The extinct flightless mihirungs (Aves, Dromornithidae): cranial anatomy, a new species, and assessment of Oligo-Miocene lineage diversity

Trevor H. Worthy; Warren D. Handley; Michael Archer; Suzanne J. Hand

—Giant flightless fowl (Aves, Dromornithidae) similar to the Northern Hemisphere gastornithids and weighing up to 350–650 kg evolved on Gondwana and existed in what is now Australia from the Eocene to the late Quaternary. Understanding cranial morphology of dromornithids has until now been based almost wholly on species of Dromornis, with that of species in three other genera either previously unknown or very fragmentary. Here we rectify this deficiency and describe a well-preserved cranium from the middle Miocene Bullock Creek Local Fauna referred to Ilbandornis woodburnei, Rich, fragmentary crania, quadrates, pterygoids, and mandibles for the Oligo-Miocene Barawertornis tedfordi Rich, and additional material of the species of Ilbandornis. The morphological similarity of this cranial material suggests that the emu-sized B. tedfordi is a smaller precursor to and differs little from species of Ilbandornis. Dromornis murrayi, n. sp., from late Oligocene–Early Miocene sites at Riversleigh, based on cranial and postcranial elements, is the oldest and smallest species in its genus. Placed in the context of other data, these observations suggest that the dromornithids comprised only two lineages throughout the Oligo-Miocene. The Barawertornis-Ilbandornis lineage attained maximum diversity in the middle Miocene Bullock Creek and late Miocene Alcoota local faunas (LF), with two species in each, but the Dromornis lineage seems to have been monotypic throughout its temporal range. The low diversity of these giant galloanseres in Australia mirrors that of the giant herbivorous ratites (ostriches and kin), which similarly have low diversity where they coevolved with diverse mammalian faunas. http://zoobank.org/urn:lsid:zoobank.org:

Journal of Vertebrate Paleontology e1031345 (21 pages) Ó by the Society of Vertebrate Paleontology DOI: 10.1080/02724634.2015.1031345 ARTICLE Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 THE EXTINCT FLIGHTLESS MIHIRUNGS (AVES, DROMORNITHIDAE): CRANIAL ANATOMY, A NEW SPECIES, AND ASSESSMENT OF OLIGO-MIOCENE LINEAGE DIVERSITY TREVOR H. WORTHY,*,1 WARREN D. HANDLEY,1 MICHAEL ARCHER,2 and SUZANNE J. HAND2 1 School of Biological Sciences, Flinders University, GPO 2100, Adelaide 5001, South Australia, Australia, trevor.worthy@flinders.edu.au; warren.handley@flinders.edu.au; 2 School of Biological Earth and Environmental Science, University of New South Wales, Sydney 2052, New South Wales, Australia, m.archer@unsw.edu.au; s.hand@unsw.edu.au ABSTRACT—Giant flightless fowl (Aves, Dromornithidae) similar to the Northern Hemisphere gastornithids and weighing up to 350–650 kg evolved on Gondwana and existed in what is now Australia from the Eocene to the late Quaternary. Understanding cranial morphology of dromornithids has until now been based almost wholly on species of Dromornis, with that of species in three other genera either previously unknown or very fragmentary. Here we rectify this deficiency and describe a well-preserved cranium from the middle Miocene Bullock Creek Local Fauna referred to Ilbandornis woodburnei, Rich, fragmentary crania, quadrates, pterygoids, and mandibles for the Oligo-Miocene Barawertornis tedfordi Rich, and additional material of the species of Ilbandornis. The morphological similarity of this cranial material suggests that the emu-sized B. tedfordi is a smaller precursor to and differs little from species of Ilbandornis. Dromornis murrayi, n. sp., from late Oligocene–Early Miocene sites at Riversleigh, based on cranial and postcranial elements, is the oldest and smallest species in its genus. Placed in the context of other data, these observations suggest that the dromornithids comprised only two lineages throughout the Oligo-Miocene. The Barawertornis-Ilbandornis lineage attained maximum diversity in the middle Miocene Bullock Creek and late Miocene Alcoota local faunas (LF), with two species in each, but the Dromornis lineage seems to have been monotypic throughout its temporal range. The low diversity of these giant galloanseres in Australia mirrors that of the giant herbivorous ratites (ostriches and kin), which similarly have low diversity where they coevolved with diverse mammalian faunas. http://zoobank.org/urn:lsid:zoobank.org:pub:591C910A- 882F-46B6-900D-20078E5A537B Citation for this article: Worthy, T. H., W. D. Handley, M. Archer, and S. J. Hand. 2016. The extinct flightless mihirungs (Aves, Dromornithidae): cranial anatomy, a new species, and assessment of Oligo-Miocene lineage diversity. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1031345. INTRODUCTION Gondwanan landmasses were home to at least two lineages of giant flightless birds in the Late Cretaceous or early Palaeogene: the ratite palaeognaths (ostrich, emu, rhea, and kin) and giant galloanseres, with Brontornis in South America and dromornithids in Australia (Agnolin, 2007; Mayr, 2009; Mitchell et al., 2014). The giant flightless fowl of Australia, the mihirungs (Aves, Dromornithidae), are much less well known than the ratites and are entirely extinct (Murray and Vickers-Rich, 2004). Seven species in four genera are recognized from the late Oligocene, Miocene, and Pleistocene (Owen, 1873; Stirling and Zietz, 1896; Rich, 1979; Nguyen et al., 2010; Worthy and Yates, 2015). Here we follow the generic arrangement advocated by Nguyen et al. (2010), except that Ilbandornis lawsoni Rich, 1979, is not transferred to Genyornis, following the recommendation of Worthy and Yates (2015). For a long time considered to be ratites (Rich, 1979), these birds came to be recognized as related to anseriforms with the discovery of cranial material (Olson, 1985; Vickers-Rich, 1991; Murray and Megirian, 1998). More recent analyses refined this anseriform relationship to sister group to *Corresponding author. Color versions of one or more of the figures in this article can be found online at www.tandfonline.com/ujvp. either Anhimidae or Anseranatidae (Murray and Vickers-Rich, 2004), although another analysis placed dromornithids as the sister group of galloanseres, i.e., the clade of galliforms and anseriforms (Mayr, 2011). Dromornithids rival and even exceed the larger ratites, such as moa (Dinornithiformes) and elephant birds (Aepyornithiformes), in size, with the smallest, Barawertornis tedfordi Rich, 1979, being about the size of an emu (Dromaius novaehollandiae) and the largest, Dromornis stirtoni Rich, 1979, estimated to have weighed 350–650 kg (Murray and VickersRich, 2004). Most were quite graviportal birds, although one, Ilbandornis lawsoni Rich, 1979, was cursorial and about the size of an ostrich (Murray and Vickers-Rich, 2004; Worthy and Yates, 2015). One of the most outstanding features of dromornithids is their cranial anatomy. To date, knowledge of this is essentially limited to Dromornis planei (Rich, 1979) and D. stirtoni because crania and bills are unknown for the other taxa or are extremely fragmentary (Murray and Megirian, 1998). The oft-referred to skull of Genyornis newtoni Stirling and Zietz, 1896, is essentially a pile of fragments, apparently carved from the sediment in an expected shape (T. H.W., pers. observ.) and, as revealed by Stirling and Zietz (1913) and inspection of the fossil (SAM P10838), the occipital condyle (displaced and oriented at 90 to expected), orbital rim, and quadratojugal are the only recognizable osseous structures, contra Murray and Vickers-Rich (2004:fig. 38), and Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-2) reveals nothing about bill morphology because no margins are preserved (T.H.W., pers. obs.). Therefore, the material of Dromornis described by Murray and Megirian (1998) provides essentially the only insight into skull structure in these birds. Dromornithids were characterized by extremely foreshortened crania, a hinge-like articulation of the bill with the cranium, and a large yet fragile bill that was elongate, very deep, and lateromedially compressed, with the tip only slightly decurved ventrally. The mandible was similarly large and deep, especially below the coronoid process. This structure is superficially very similar to that of the Eocene Gastornis (D Diatryma) gigantea Cope, 1876, from the Northern Hemisphere, as revealed by the type of Diatryma steini Matthew and Granger, 1917, now synonymized with D. gigantea (Brodkorb, 1967; Andors, 1992; Buffetaut, 2004). Matthew and Granger (1917) dismissed similarity with dromornithids, being misled by the image in Stirling and Zietz (1913) for G. newtoni, but both birds share the deep highly compressed bill with rudimentary nares and a well-formed prokinetic hinge between the cranium and bill. In the same way as for dromornithids, Gastornis species are recognized as giant fowl related to anseriforms (Andors, 1992), and both are giant herbivores (Andors, 1992; Murray and Vickers-Rich, 2004; Angst et al., 2014), contra Witmer and Rose (1991). The only cranial material referred to Ilbandornis has until now been a badly crushed and distorted cranium from the Alcoota Local Fauna (LF), fragments of mandibles, and partial quadrates and pterygoids (Murray and Megirian, 1998; Murray and Vickers-Rich, 2004). The cranium from the Alcoota LF features a bizarre structure where the supraoccipital area markedly overhangs the condylus occipitalis posteriorly, although it is unclear how much of this is a real feature and how much the result of a taphonomic distortion (Murray and Vickers-Rich, 2004). A small fragment of a cranium from Bullock Creek of similar size to the Alcoota Ilbandornis cranium was referred to ?Bullockornis sp. by Murray and Vickers-Rich (2004). In the light of these observations, a new essentially complete and undistorted cranium referable to an Ilbandornis species is significant for the potential it has to shed light on cranial morphology of the genus and on intergeneric cranial diversity of dromornithids. Furthermore, undescribed cranial material recently prepared from sites in the Riversleigh World Heritage Area represents two taxa. Material of a small species is assignable to Barawertornis tedfordi, whereas that of a large species represents a new species of Dromornis. The aim of this contribution is therefore to describe these new cranial materials, describe the new species of Dromornis, and assess cranial morphology and lineage diversity through time and the hypothesis that diversity of these large flightless herbivorous birds was constrained by mammalian diversity (Mitchell et al., 2014). The material described and compared herein derives from three site complexes. The new cranium attributed to Ilbandornis and other material described below form part of the Bullock Creek LF that derives from the Camfield Beds at Bullock Creek, Northern Territory, and is middle Miocene in age, between 15 and 12 Ma old, based on biochronological considerations (Megirian, 1992; Murray and Megirian, 1992; Murray and Vickers-Rich, 2004; Megirian et al., 2010; Woodhead et al., 2016). It forms the type locality for the Camfieldian Land Mammal Age (Megirian et al., 2010). This fauna contains Dromornis planei and two species of Ilbandornis (I. cf. I. lawsoni and I. cf. I. woodburnei) (Rich, 1979; Murray and Vickers-Rich, 2004; Worthy and Yates, 2015). The fauna is derived from freshwater limestone, the material is well preserved and undistorted, and it was the source for the extraordinary material described by Murray and Megirian (1998). The second site complex producing material described herein is that at Alcoota, in the Northern Territory. Material from here is termed the Alcoota LF, derives from the Waite Formation (Woodburne, 1967), and is about 9–7 Ma (Murray and VickersRich, 2004; Megirian et al., 2010). Alcoota is the type locality of D. stirtoni Rich, 1979, Ilbandornis woodburnei Rich, 1979, and Ilbandornis? lawsoni Rich, 1979 (Rich, 1979; Murray and Vickers-Rich, 2004). Fossils from this site are much more poorly preserved than those from Bullock Creek due to their shallow interment in unconsolidated clays and silts. Repeated wetting and drying of this deposit has led to complete fracturing and partial crushing of most specimens. Alcoota is important as the principal site known from mainland Australia that samples late Miocene terrestrial vertebrates (Woodhead et al., 2016) and is recognized as the type locality of the Waitean Land Mammal Age (Megirian et al., 2010). The remaining new material described here derives from the late Oligocene–early Miocene freshwater limestone deposits in the Riversleigh World Heritage Area, Boodjamulla (Lawn Hill) National Park, in northwestern Queensland, Australia. The material mainly derives from Hiatus Site (Queensland Museum Locality 941), Hals Hill, D Site Plateau (Archer et al., 1989, 1994; Creaser, 1997; Travouillon et al., 2006). The site is considered part of Riversleigh’s Faunal Zone A deposits, which, based on stage of evolution of contained mammal taxa and faunal correlation, are late Oligocene–early Miocene (25–23 Ma) in age (Archer et al., 1997, 2006; Creaser, 1997; Travouillon et al., 2006; Woodhead et al., 2016). Other material described from Riversleigh is mainly from Neville’s Garden Site, a cave deposit considered part of Faunal Zone B (Archer et al., 1997, 2006; Travouillon et al., 2006) and recently given an absolute date in the early Miocene (18.24 § 0.29 to 17.85 § 0.13 Ma) (Woodhead et al., 2016). Some material is also described from White Hunter Site, Hals Hill, of Faunal Zone A. Deposits attributed to Faunal Zone A are the source for Barawertornis tedfordi Rich, 1979, but the species is also frequent in Faunal Zone B sites (Nguyen et al., 2010). Some taxa from Faunal Zone A at Riversleigh have also been collected from the upper part of the Etadunna Formation (e.g., the ilariid Kuterintja ngama Pledge [see Myers and Archer, 1997] and the diprotodontoid Ngapakaldia bonythoni Stirton [see Black, 2010]). The Etadunna Formation has been dated using a range of techniques as late Oligocene in age (Woodburne et al., 1994), so the Faunal Zone A deposits from Riversleigh are likely to be late Oligocene in age also (Woodhead et al., 2016). MATERIALS AND METHODS Cranial material of dromornithid taxa were examined in museum and university collections, particularly those of the AM, AR, NTM, QM, and QVM, and loaned to T.H.W. at Flinders University. Additional specimens were sourced from the collection held at the Outback at Isa, Mount Isa, Queensland, which are part of the QM collections. These specimens had been prepared from Riversleigh limestone by John Scanlon. Qualitative features that might distinguish taxa were sought by comparative observations. Measurements were made with dial callipers to the nearest 0.1 mm and rounded to the nearest mm. Measurements common to femora, tibiotarsi, and tarsometatarsi included total length, minimum shaft width, and maximum distal width. Total length for tibiotarsi was taken from the tip of the crista cnemialis cranialis to the distal end of the condylus lateralis. For femora, the proximal width was taken in proximal view as the width of a line extending from the caput through the middepth of the collum femoris to the lateral facies. Proximal width of tibiotarsi was taken across the articular surfaces and for tarsometatarsi was maximum lateromedial width. We use the anatomical nomenclature for specific bone landmarks advocated by Baumel and Witmer (1993). Terminology for cranial musculature follows Lautenschlager et al. (2014). Institutional Abbreviations—AM, Australian Museum, Sydney, New South Wales; AR, the palaeontology collections of the Worthy et al.—Oligo-Miocene dromornithids (e1031345-3) Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Palaeontology Laboratory in the School of Biological Earth and Environmental Sciences at University of New South Wales, Sydney, New South Wales; FU, Palaeontology Laboratories, Flinders University, Adelaide, South Australia; NTM, Museum of Central Australia, Alice Springs, Northern Territory; QM, Queensland Museum, Brisbane, Queensland; QVM, Queen Victoria Museum and Art Gallery, Launceston, Tasmania; SAM, South Australian Museum, Adelaide, South Australia. Measurements—DW, distal width; PD, proximal depth; PW, proximal width; SD, shaft depth; SW, shaft width. Anatomical Abbreviations—lig., ligamentum; mm, musculus; n, nervi; v, veni. SYSTEMATIC PALEONTOLOGY ILBANDORNIS Rich, 1979 ILBANDORNIS WOODBURNEI Rich, 1979 (Fig. 1) Material Bullock Creek Local Fauna—QVM:2000:GFV:20, cranium lacking zona flexoria craniofacialis, right processus paroccipitalis, and rostrum parasphenoidalis and associated processus basipterygoidei (Fig. 1); measurements—see Description of Cranium. NTM P8765-1, a fragment preserving the basioccipital area; condylus occipitalis width D 13.2 mm, condylus occipitalis height D 11.1 mm. NTM P8695-273, a fragment preserving the condylus occipitalis, listed by Murray and Megirian (1998:66) as Bullockornis sp.; occipital condyle width D 12.6 mm, condylus occipitalis height D 11.0 mm. Description of Cranium The following description is based mainly on QVM:2000: GFV:20. Measurements—QVM:2000:GFV:20; width between orbits D 106.6 mm, width across ossa exoccipitales D 88.3 mm, width condylus occipitalis D 13.1 mm, height condylus occipitalis D 12.4 mm, height foramen magnum D 20.1 mm, maximum width foramen magnum (ventrally) D 11.4 mm, width between lateral margins of recessus quadratica D 75.5 mm, length recessus quadratica D 14.0 mm, width recessus quadratica D 12.4 mm, length tip processus zygomaticus to angle of os exoccipitale D 74.7 mm, height processus paroccipitalis to crista nuchalis transversus medially D 117.0 mm. Lateral Aspect—As in Dromornis, the cranium is dorsoventrally deep and rostrocaudally very short (Fig. 1A). The QMV cranium preserves the entire orbital margin, so if it had a similar morphology to that of Dromornis, breakage has resulted in the loss of only the zona flexoria craniofacialis and very little else. The junction of the crista supraorbitalis and the processus postorbitalis is a shallow notch in lateral view. The crista supraorbitalis is penetrated by a series of foramina that extend from within the orbit to the dorsolateral surface of the cranium, and it projects rostrally of the caudal wall of the orbit by about 15 mm. The processus postorbitalis and processus zygomaticus are fused together over their entire length (Fig. 1A), in contrast to the partial fusion seen in some galliforms, but similar to the situation in Anhima. The processus zygomaticus, described as the “squamosal eminence of the quadratic fossa and the laterosphenoid” by Murray and Megirian (1998:56), is developed rostrally by ossified aponeuroses that extend below the orbit. The side of the cranium bears a shallow fossa temporalis that extends caudally from the processus postorbitalis to the midlength of the cavum tympanicum and dorsally to about level with the ventral third of orbit. The fossa temporalis is thus located differently to that of most birds, in which it lies between the processus postorbitalis and processus zygomaticus. Nevertheless, this is presumed to be the insertion area for m. abductor mandibulae externus pars articularis (see Zusi and Livezey, 2000). It is deepest where it abuts the lateral wall of the recessus quadratica (new term, for the reception of the globular processus oticus of the quadrate on which the capituli oticum et squamosum are undifferentiated). Immediately caudal to this recess, a robust conical processus suprameaticus that is round in section and 8 mm long by 7 mm wide extends ventrorostrally. The ventral margin of this process therefore forms the roof of the cavum tympanicum. Extending from the rostral tip of the processus suprameaticus, a twisted sliver of bone encloses the cavum rostrally by connecting ventrally to the robust processus lateralis parasphenoidalis that is continuous caudally with the base of the processus paroccipitalis. A rugose elevation is situated at the caudodorsal corner of the cavum tympanicum and lateral to the base of the processus suprameaticus. The cavum tympanicum is elongate rostrocaudally (20 mm long by 13 mm high) with a solid dorsally-concave floor. Within the cavum, the pila oticum is robust, mediolaterally broad, bounded laterally by an oval foramen, and aligned horizontally (i.e., parallel to the basioccipital). The pila oticum is bounded medially by two large recesses, with a broad funnel-like opening of the tubita auditiva situated ventromedially. The more caudal recess (recessus columellae) is »5 mm in diameter. Just rostral to this is the recessus tympanicus rostralis that is divided internally into equal-sized lateral and medial halves. The processus paroccipitalis is robust (Fig. 1C), extends 35 mm ventral to the cavum tympanicum, and is triangular in lateral view with a somewhat flattened rostral margin and a rounded caudal side. The caudal profile of the processus paroccipitalis and os exoccipitale forms a nearly straight line that extends to an angle on the caudal margin that marks the junction with the cristae nuchalis lateralis et transversus. Damage to the supraoccipital area precludes knowledge of the presence or size of a supraoccipital prominence, but it would have been a slight swelling at most, because the available area is small and the area enclosed rostrally by the cristae lateralis et transversus is flattened and sloped forward dorsal to the foramen magnum. There cannot have been a large, caudally-directed prominence as suggested for the Alcoota cranium of Ilbandornis NTM P9843 by Murray and Megirian (1998). There is no supraoccipital prominence in Dromornis. Caudal Aspect—The dorsal half of the cranium is evenly rounded in profile (Fig. 1C). The condylus occipitalis (13.2 mm wide and 12.4 mm high) is situated at approximately mid-height between the tip of the processus paroccipitalis and the dorsal surface of the cranium, flattened dorsally with no incisura, and without a constricted neck. The foramen magnum is dorsoventrally elongate, with subparallel sides 20 mm high by 11 wide at middepth. At the boundary of the os exoccipitale and os parietale, midway between the condylus occipitalis and the prominence on the os exoccipitale laterally, the foramen v. occipitalis externae opens from a dorsally-projecting canal. The ossa exoccipitales are robustly developed caudolaterally so that a line connecting their caudal margin passes just caudad of the condylus occipitalis, thereby encompassing the foramen magnum within a broad shallow fossa. The maximum width across the ossa exoccipitales is level with the condylus occipitalis, with the lateral margin joining the processus paroccipitalis at a wide angle. The QMV specimen and the similar-sized NTM P8765-1 both preserve the area ventral to the condylus occipitalis and the foramina for the exits of the cranial nerves and veins/arteries (Fig. 1E, F). Foramina n. hypoglossi (XII) are closest to the condylus and level with the mid-height of the condylar neck, with those on each side being » 18 mm from one another across the midline. Another, similarly small foramen (paired on the left side) is located about 7 mm ventral to this foramen and Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-4) FIGURE 1. Crania of Ilbandornis woodburnei QMV:2000:GFV:20 (A, C–F) and Dromornis planei NTM P9464-106 (B, G–H) from Bullock Creek, Northern Territory, in lateral (A, B), rostroventral (D, H), ventral (E, F), and posterior (C, G) views. Abbreviations: co, condylus occipitalis; coe, ostium for canalis opthalmici externi (VI); cs, crista supraorbitalis; ct, cavum tympanicum; ep, exoccipital prominence; fm, foramen magnum; fo, foramen for n. opticum; foe, foramen v. occipitalis externae; ft, fossa temporalis; lf, lacerate (presphenoid) fossa; lp, lamina parasphenoidalis; ma, insertion area for m. adductor mandibulae externus medialis et superficialis; mrcd, insertion for branch of m. rectus capitus dorsalis; mrcv, insertion m. rectus capitus ventralis; mt, mamillar tuberosities; op, ostium pharyngeale; pb, processus basipterygoidei; po, processus postorbitalis; pp, processus paroccipitalis; ps, processus suprameaticus; pts, insertion for m. pseudotemporalis superficialis; pz, processus zygomaticus; rp, rostrum parasphenoidalis; rq, recessus quadratica; tf, trigeminal foramen or foramen n. maxillomandibularis, for cranial nerves V2 and V3; zfc, zona flexoria craniofacialis; III, foramen for n. occulomotorii (III); VII, ostium canalis carotici and branch nerve VII, VIIr, foramen for rostral opening nerve VII; IX, foramen n. glossopharyngeus (IX); X, foramen n. vagi (X); XII, foramina for n. hypoglossi (XII). Scale bars equal 10 cm, apply to all, except F (magnification D 200%). Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-5) represents the second exit of cranial nerve XII. This is located along a line that would pass mesad of the mamillar tuberosities. Two exits for XII are normal in Galloanseres. Located about 5 mm laterad of these last two foramina are three larger foramina aligned in a dorsoventrally arranged row, with a yet larger fourth foramen immediately lateral of these. The most dorsally located in the line of three is the foramen n. vagi (X), with the middle position representing the foramen n. glossopharyngeus (IX). The most ventral foramen of the triad is the ostium canalis carotici that transmits the carotid and a branch of cranial nerve VII, and is separated from its counterpart by 30 mm. The lateralmost foramen is the ostium canalis opthalmici externi for the ophthalmic arteries and veins. The mamillar tuberosities are relatively low and » 8 mm wide. They are slightly elevated caudally such that a notch in which the carotid would have passed separates them from the processus paroccipitalis. The mamillar tuberosities merge with the os parasphenoidale anteriorly and form a rounded fossa medially. The mamillar tuberosities mark the insertions for the neck muscle m. rectus capitis ventralis that originates via a series of slips on cervical vertebrae 2–4. Between the tuberosities are smaller elongate (3.8 mm by 8 mm) insertion scars for a part of the m. rectus capitis ventralis. Closer to the condylus occipitalis are a third pair of insertions (» 5 mm in diameter) that abut each other medially and are presumed to be for a branch of m. rectus capitis dorsalis. A shallow fossa is present between these and the base of the condylus occipitalis, as noted by Murray and Megirian (1998). Ventral Aspect—The entire lamina parasphenoidalis is preserved in the QMV specimen (Fig. 1E). It projects rostrally as a point about 33 mm anterior to a line connecting the two mamillar tuberosities. The rostrum parasphenoidalis is broken off, but two grooves, interpreted as the canalis ramus palatinus, extend from the base of the processus paroccipitalis into the ostium pharyngeale. The ostium is broad, dorsoventrally flattened, and contains the the openings of the tubita auditiva; the latter nearly meet medially and are mostly obscured by the lamina parasphenoidalis. Ventrorostral Aspect—The recessus quadratica (new term) is located between the processus suprameaticus caudally and the processus zygomaticus rostrally (Fig. 1D, E). The cotylae quadratici otici et squamosi are merged to form one rounded cotyla within recessus quadratica. The cotyla quadratica otici is buttressed by the pila oticum and partly separated by a notch from the rostroventral part of cotyla quadratica squamosi. The recessus is elongate along a laterorostral to caudomedial plane and is 14 mm long by 11 mm wide. Opening within the notch and between the two cotylae is the exit for nerve VII. Mesad of the recessus quadratica and level with a line linking the base of the processus zygomaticus is a large (4 mm) foramen n. maxillomandibularis, or trigeminal foramen that transmits cranial nerves V2 and V3. Immediately rostral to this foramen is a conical tuberosity that is interpreted as the insertion for musculus pseudotemporalis superficialis (Lautenschlager et al., 2014). Lateral to this tuberosity is a large and deep fossa extending anterior to the base of the processus zygomaticus. This housed the insertion for the musculi adductor mandibulae externus medialis et superficialis. These muscles usually insert in the fossa temporalis on the lateral side of the cranium in most birds, but in anseriforms insert within the orbit on the processus postorbitalis (Zusi and Livezey, 2000). Abutting the base of the rostrum parasphenoidalis are a set of foramina for the exit of cranial nerves. Closest to the rostrum and most ventrally located is the foramen n. oculomotorii (III) which is » 2 mm in diameter. The foramen n. opticum is the largest of the group (ca. 6.8 mm) and is located 4 mm dorsal to the foramen of III. Caudally to these is a presphenoid or lacerate fossa that includes three foramina, interpreted here to include the foramen n. opthalmici (D abducent) or VI and a branch of V1 (Fig. 1D). Another small foramen opens about 7 mm dorsal to the lacerate fossa, and is likely the foramen n. trochlearis (IV). The orbit is 48 mm wide from the anterior boundary formed by the rostrum, 45 mm long from the anterior side of the processus zygomaticus, and deepest dorsolaterally where the crista orbitalis is broadest. Numerous nutrient foramina penetrate the walls of the orbit at this point and lead to exits dorsally on the cranium. Comments—Worthy and Yates (2015) referred postcranial bones from Bullock Creek to the two species of Ilbandornis known from the Alcoota LF, I. lawsoni and I. woodburnei. Those of the former species are on average smaller and more gracile than those of the latter. The Bullock Creek cranium QVM:2000: GFV:20 is here referred to Ilbandornis woodburnei on the basis that it represents the larger of two cranial forms of ‘small’ dromornithids found at the site. For example, the width of its condylus occipitalis (13.1 mm) is only exceeded by that of NTM P8765-1 (13.2 mm), which has a very similar basioccipital morphology and so is considered to be the same taxon. As discussed below, there are other cranial fragments of considerably smaller dromornithids that likely pertain to the Ilbandornis lawsoni lineage. ILBANDORNIS, sp. indet. Material: Bullock Creek Local Fauna Cranial Fragments—NTM P907-27, right side of cranium preserving part of the orbit, processus postorbitalis, processus suprameaticus, cavum tympanicum, and recessus quadratica that was depicted by Murray and Vickers-Rich (2004:fig. 91A, D) as ?Bullockornis sp. (Fig. 2A–D). NTM P87103-44, a fragment preserving the condylus occipitalis, listed by Murray and Megirian (1998:66) as Bullockornis sp., condylus occipitalis width D 11.8 mm. NTM P9464-262, occipital fragment, condylus occipitalis width D 15.2 mm. Mandibles—NTM P2774-2, partial right ramus mandible (Fig. 3A, B); NTM P2775, partial left ramus mandible. Quadrates—NTM P991-x, a worn right quadrate. Pterygoids—NTM P9973-8, left complete except for sliver off medial side of facies articularis basipterygoidea. Material: Alcoota Local Fauna Cranial Fragments—NTM P9843, a rather distorted and crushed cranium with width between recessus quadratica D 70 mm and width condylus occipitalis D 13.1 mm; see Murray and Megirian (1998) and Murray and Vickers-Rich (2004:111– 112, figs. 91, 92). Occipital fragments: NTM P4518, condylus occipitalis width D 10 mm; NTM P98108, condylus occipitalis width D 12.8 mm; and five unregistered fragments with condylus occipitalis widths D 10.1, 13.4, 15.7, and 17.0 mm. Quadrates—NTM P3231, processus oticus of quadrate; NTM P3235, right quadrate lacking processus orbitalis, height D 39.9 mm, width condylus lateralis D 9.7 mm, maximum width otic capitulum D 11.2C mm; NTM P3236, left quadrate, lacking condylus medialis, height D 41.8 mm; NTM P3237, left quadrate lacking processus orbitalis, height D 39 mm, width condylus lateralis D 8.4 mm, maximum width otic capitulum D 11.9 mm; NTM P3238, left quadrate, height D 35.5 mm; NTM P98116, partial left quadrate. Pterygoids—NTM P3239, partial right missing quadratic articular area; NTM P3240, right missing rostral half and broken through facies articularis basipterygoidea. Description Cranium—The available fragments offer little information besides that covered in the description above for I. woodburnei. However, the material listed above includes specimens that Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-6) represent considerably smaller individuals than those referred to I. woodburnei e.g., NTM P907-27 and NTM P87103-44 with an occipital condylar width of 11.8 mm. The former lacks a condylus occipitalis but is from a smaller individual, width recessus quadratica 12.5 mm versus 14 mm in QVM:2000:GFV:20, and has a more prominent processus suprameaticus (Fig. 2A–D). These latter two specimens are therefore likely to be from the other smaller Ilbandornis species in the site, I. lawsoni. Murray and Vickers-Rich (2004:111:figs. 91, 92) noted the similarity of NTM P907-27 to the Alcoota specimen NTM P9843, referring both to I. woodburnei, but at that time did not recognize that two Ilbandornis species coexisted at Bullock Creek. Specimen NTM P9843 was described by Murray and Megirian (1998) and again by Murray and Vickers-Rich (2004:111–112, fig. 92), so a detailed description will not be repeated here. However, it has a condylus occipitalis 12.5 mm wide and 13.5 mm deep, so it is slightly smaller than QVM:2000:GFV:20 referred above to I. woodburnei. Its size is otherwise difficult to assess, because it is mediolaterally crushed and is missing most of the right side and the left paroccipital area. Importantly, the cranium is distorted dorsally, with what was likely the right lateral side preserved as a protuberance overhanging the caudal region. Given the nature of Alcoota material, which is typically highly fractured, the breakage zone was not recognized as an artefact of preservation. Specimens QVM:2000:GFV:20 and NTM P907-27 reveal that the crania of Ilbandornis taxa are very similar to those of Dromornis, and it is unlikely that such a caudally overhanging crest was a real feature of crania of Ilbandornis at Alcoota. However, one significant feature is discernible in NTM P9843. The form of the processus suprameaticus (i.e., conical, round in section, and elongate) is similar to NTM P907-27, which we here refer to I. lawsoni. Therefore, NTM P9843 is tentatively referred to I. lawsoni. Until more complete fossils are available, it seems that crania of Ilbandornis species differ little from each other except for the morphology around the processus suprameaticus. The occipital fragment NTM P9464-262 that preserves a large condylus occipitalis (width at 15.2 mm) is considerably larger than QVM:2000:GFV:20, yet seems too small to be a Dromornis species. The incomplete nature of this specimen precludes certain referral to either genus at this time. Several specimens from the Alcoota LF preserving the condylus occipitalis indicate a size range for small dromornithid crania that reflect the two species of Ilbandornis, but there is currently insufficient data to discriminate between them. Mandible—NTM P2774-2 is well preserved but lacks the tip and symphyseal zone, processus retroarticularis and processus medialis mandibulare (Fig. 3A, B). Measurements: height at processus coronoideus D 62 mm; length processus coronoideus to anterior side cotylae D 44 mm; width across cotylae D 21.8 mm; length cotyla lateralis D 23 mm. A fenestra caudalis mandibulae is present and is 25.8 mm long by 6.3 mm high. This fenestra lies lateral to and immediately above an elongate shelf that is interpreted as the dorsal margin of os prearticulare and is slightly higher than mid-height of the mandible. This shelf ventrally bounds the fossa aditus canalis mandibularis that is about 80 mm long and extends both rostral and caudal to the fenestra. The angulus mandibulae is coincident with the processus coronoideus and marks the deepest part of the mandible and shows that the rhamphothecal sheath extended well caudad of its midlength. The process that Murray and Megirian (1998) called the coronoid process is a minor secondary aponeurosis and not the primary aponeurosis of the m. adductor mandibulae externus. The processus coronoideus is most elevated at the caudal end of the fenestra, with this point also matching the maximal ventral expansion of the mandible. Rostral to the maximal coronoid elevation, the os supra-angulare is fully fused to the os dentale and the conjoined elements thicken rostrally on the dorsal margin. Over the rostral 20 mm, a crest representing the tomial margin is preserved. It is flanked medially by a flat facet indicative of a former shearing zone of the mandible. The cotylae are shallow with a laterally convex cotyla lateralis, whereas in D. planei (NTM P2774-3) it is sharply angular. The cotylae lateralis et medialis are adjacent to one another, separated by a low crista intercotylaris that is aligned at ca. 30 from the ramal axis. The cotyla medialis mandibularis is substantially deeper than its lateral counterpart. The processus medialis mandibulae extends medially from the upper two-thirds of the depth of the mandible, with the corpus below it robust and rounded ventrally. There is no fossa caudalis or recessus conicalis. A pair of nutrient foramina are present in the middle of the robust lower part of the mandible at the caudal end of the fenestra, representing a point that presumably marks the boundary of the os angulare and os prearticulare. At present, NTM P2774-2 is referred to an indeterminate species of Ilbandornis, given that there is not a clear second morphotype in this size range for comparison. Quadrate—The quadrates from the Alcoota LF referred to Ilbandornis have the following features as exemplified by NTM P3235 and P3237 (Fig. 4G, H): height from top of processus oticus to mandibular condyles D 39–40 mm (although other specimens listed above range 35.5–41.5 mm); capitulum squamosum and capitulum oticum are merged, lacking an intercapitula vallecula; the capitulum oticum overhangs the medial facies, the capitulum squamosum does not overhang the lateral facies; the medial facies is concave; a foramen pneumaticum rostromediale is present, a low crista medialis defines its caudal margin, another low crista defines its rostral margin and passes ventrally to merge with the crista medialis and become the caudal boundary of a broad fossa basiorbitalis; a robust tuberculum subcapitulare extends 12–13 mm rostroventrally, enclosing a distinct elongate fossa dorsal to it; the pars quadratojugalis of the lateral process meets the caudal facies of the corpus at a right angle, lacks a prominentia submeatica, and is concave medially; the fovea quadratojugalis is shallow, marked by an elevated crest anteriorly, located so that it forms the dorsal and caudal margins of the pars quadratojugalis of the lateral process and is widely separated from the condylus mandibularis lateralis, and the plane of the fovea is set at about 45 to the alignment of the mandibular condyles; the condyli mandibularis lateralis et medialis are oval, overlap by about a third of their length, are ventrally flattened, and are barely separated by an intervening groove; and the condylus pterygoideus is a rounded projection directed dorsolaterally from the condylus medialis, with the articular facet for the pterygoids extending from it around the notch at the base of the processus orbitalis. Whether a separate facies for the pterygoids was present on the processus orbitalis cannot be assessed. Both of these quadrates are too small to be associated with a skull the size of QVM:2000:GFV:20, as judged by the loose fit of the processus oticus into the recessus quadratica in the cranium; however, NTM P3236 with a height 41.8 mm is a better size match. This size disparity suggests that both quadrates NTM P3235 and P3237 may belong to the smaller I. lawsoni. Pterygoid—The specimens NTM P9973-8 (a left pterygoid from Bullock Creek LF) and NTM P3239 (partial right pterygoid, missing the caudal quadratic articular portion) and NTM P3240 (right pterygoid missing the palatine articulation), both from Alcoota LF, inform the morphology of this element for Ilbandornis. They are not much shorter, but are differentiated from those attributed to species of Dromornis by being much more gracile, with especially smaller cotyla for articulation with the quadrate. Specimen NTM P9973.8 is 46.6 mm long, 18.4 mm across the palatine articulation, with the articulation for the facies articularis basipterygoidea at 18.6 mm long. About half of the length is posterior to the facies articularis basipterygoidea. The dorsal side of the ‘shaft’ has a shallow sulcus in it, and the medial facies has an elongate sulcus where it ventrally overlaps Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-7) FIGURE 2. Crania fragments of Ilbandornis sp. ?I. lawsoni NTM P907-27 from Bullock Creek, Northern Territory (A–D), Barawertornis tedfordi QM F58013 from Hiatus Site, Riversleigh (E, F), Ilbandornis woodburnei QMV:2000:GFV:20 from Bullock Creek, Northern Territory (G), and Dromornis planei NTM P9464-106 from Bullock Creek, Northern Territory (H), in ventrolateral (A, G), mirrored (H), right lateral (B), lateroventrorostral (C), ventral (D, E), and posterior (F) views. Abbreviations: co, condylus occipitalis; coe, ostium for canalis opthalmici externi (VI); cs, crista supraorbitalis; ct, cavum tympanicum; ep, exoccipital prominence; fm, foramen magnum; ft, fossa temporalis; ma, insertion area for m. adductor mandibulae externus medialis et superficialis; pb, processus basipterygoidei; po, processus postorbitalis; pot, pila otica; pp, processus paroccipitalis; ps, processus suprameaticus; pts, insertion for m. pseudotemporalis superficialis; pz, processus zygomaticus; rq, recessus quadratica; tf, trigeminal foramen or foramen n. maxillomandibularis, for cranial nerves V2 and V3. Scale bars equal 10 cm. Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-8) FIGURE 3. Mandibles of Ilbandornis sp. NTM P2774-2 from Bullock Creek, Northern Territory (A, B), Dromornis murrayi, n. sp., QM F57986 Hiatus Site, Riversleigh (C, D), and Barawertornis tedfordi QM F57895 from Neville’s Garden Site, Riversleigh (E–G), in medial (A, G), dorsal (B, D–F) and lateral (C) views. E–G coated in ammonium chloride, and fossil prepared by voids in limestone where bone eroded away being filled with resin before acid preparation, so preserving true thickness of rami. Abbreviations: am, angulus mandibularis; clm, cotyla lateralis mandibularis; cmm, cotyla medialis mandibularis; facm, fossa aditus canalis mandibularis; fcm, fenestra caudalis mandibularis; fpm, foramen in processus medialis mandibularis; pc, processus coronoideus; pm, processus medialis mandibulae; pr, processus retroarticularis. Scale bars equal 10 cm. Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-9) FIGURE 4. Left quadrates of Dromornis murrayi, n. sp., paratype, QM F57985 from Hiatus Site, Riversleigh (A, B), D. planei NTM P9464-100 from Bullock Creek (C, D), D. stirtoni NTM P3202 from Alcoota (E, F), and Ilbandornis sp. NTM P3237 from Alcoota (G, H) in lateral (A, C, E, G) and medial (B, D, F, H) views, all coated in ammonium chloride. Abbreviations: cm, crista medialis; cml, condylus mandibularis lateralis; cmm, condylus mandibularis medialis; co, capitulum oticum; cp, condylus pterygoideus; cs, capitulum squamosum; fb, fossa basiorbitalis; fpr, foramen pneumaticum rostromediale; fq, fovea quadrateojugalis; paf pterygoid articular facet; po, processus orbitalis; ts, tuberculum subcapitulare. Scale bar equals 20 mm. the facies articularis basipterygoidea. The palatine articulation is roughly square of the axis of the bone and allowed only a simple abutment with the palatine, although the articular surface extends onto the lateral facet. The facies articularis basipterygoidea is located close to the rostral end but does not reach as far as the palatine articulation zone. Damage on the dorsal surface of the quadratic end precludes as assessment of the extent of the processus that projects dorsally. This process would project towards the base of processus orbitalis on the quadrate when these bones were articulated. A similar processus is seen in D. planei NTM P9970.1 and in QM F24124, attributed to Barawertornis tedfordi as discussed below. processus coronoideus to rostral side of cotyla quadratica D 75 mm; NTM P9464-112, complete mandible (see Murray and Megirian [1998:figs. 11, 12] and Murray and Vickers-Rich [2004: figs. 83, 84]), missing right quadrate articular zone, length to rostral side of cotyla quadratica D 305 mm, depth at processus coronoideus D 115 mm, caudal margin of processus retroarticularis and ascending tip lost; NTM P9464-112, mandible tip; NTM P9464-113, mandible tip, symphyseal length D 68 mm (Murray and Megirian [1998:fig. 1]); NTM P9464-114, partial mandible; NTM P9464-116, partial mandible; NTM P9464-265, rostral tip mandible. Description DROMORNIS Owen, 1872 DROMORNIS PLANEI (Rich, 1979) Material Cranial Material—NTM P907-6, two fragments of a cranium; NTM P9276-4, fragment with condylus occipitalis; NTM P9464106, cranium (Fig. 1B, G, H); NTM P9464-109, cranium; NTM P9464-110, cranial fragment; NTM P9464-111, cranial fragment; NTM P9464-263, a highly abraded small fragment preserving the condylus occipitalis with width about 14.5 mm; NTM P9464-264, a fragment preserving the condylus occipitalis with width of 18.7 mm; NTM P9612-1, partial cranium; NTM P9973-1, fragment with condylus occipitalis; NTM P9973-6, cranium. Quadrates—NTM P9464-100, left quadrate lacking the caudal half processus lateralis and processus orbitalis, height D 60 mm, width mandibular condyli D 16.3 mm, maximum width of capitulum oticum D 18.4 mm (Fig. 4C, D); NTM P9464-118, left quadrate, height D 50.4 mm, width mandibular condyli D 16.1 mm, maximum width capitulum oticum D 17.9 mm. Pterygoids—NTM P87103-43, partial left; NTM P9464-101, partial right; NTM P9464-102, partial; NTM P9464-127, left; NTM P9970-1, right. Mandibles—NTM P2771, anterior tip and partial right side; NTM P2772, left ramus lacking cotylae; NTM P2774-3, right ramus, depth at processus coronoideus D 115 mm, length Crania—Crania of Dromornis were comprehensively described by Murray and Megirian (1998) based on well-preserved material of D. planei, as Bullockornis, and the somewhat less well preserved material of D. stirtoni. Here, because the cranium of Ilbandornis differs from that of D. planei in relatively subtle ways, mainly relating to their size disparity, only those features differentiating the taxa will be described. The cranium of D. planei, as best exemplified by NTM P9464106 (Fig. 1B, G, H), with an orbital width of 117 mm, is from the smaller sex of this species, with larger individuals reaching 136 mm for the comparable measurement, e.g., NTM P9464-111 (Table 1). Crania of Dromornis planei differ from those of Ilbandornis woodburnei as follows: (1) The fossa temporalis is notably larger, extending caudally to the rugosity at the dorsocaudal corner of the cavum tympanicum (Fig. 1B). (2) The processus suprameaticus is reduced to a lateromedially thin sliver because of the caudal extension of the fossa temporalis (Fig. 1B); however, it is still connected by a twisted sliver of bone to the processus lateralis parasphenoidalis, whereas in Ilbandornis it is larger and conical in section. (3) The cavum tympanicum is more rounded, whereas in Ilbandornis its long axis is aligned rostrocaudally and it is slightly dorsoventrally compressed (Fig. 1B). (4) The processus paroccipitalis has a compressed flange on its anteromedial margin (Fig. 1H) that is lacking in I. woodburnei. (5) In lateral view, the processus paroccipitalis meets the caudal margin of the os exoccipitale at a greater angle, creating a Worthy et al.—Oligo-Miocene dromornithids (e1031345-10) Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 TABLE 1. Measurements (mm) of Dromornis stirtoni and D. planei from NTM collection compared with those of D. murrayi QM F57984. Taxon Catalog no. OrbW POP OccW OccH QSW CranH D. stirtoni D. stirtoni D. stirtoni D. stirtoni D. stirtoni D. stirtoni D. planei D. planei D. planei D. planei D. planei D. planei D. planei D. planei D. planei D. murrayi P3250 P98105 P3251 P9342 P98106 P3249 P9464-109 P9464-106 P9973.6 P9464-xx P9612-1 P9276-4 P907-6 P9464-111 P9973-1 QM F57984 127.9 137.0 111.0 ca. 117.0 23.4 20.6 97.0 105.0 136.0 26.5 23.8 24.3 21.5 19.9 24.0 23.7 18.4 20.8 23.1 22.3 22.2 20.1 19.9 22.5 22.4 15.8 18.4 22.4 20.7 19.7 18.0 125.0 141.0 114.4 117.0 126.0 ca. 93.0 105.5 135.7 105.0 96.0 130.0 121.0 91.1 102.5 92.4 ZFC 91.0 165.0 105.8 115.0 117.7 84.0 89.5 108.3 103.0 ‘ca.’ means the measurement was estimated because some of the structure was missing. Abbreviations: CranH, height of crania from mamillar tuberosities to top of cranium; OccW, width condylus occipitalis; OccH, height of condylus occipitalis; OrbW, width across the orbits; POP, width across the processus paroccipitalis; QSW, width between lateral margins of recessus quadratica; ZFC, width zona flexoria craniofacialis. marked notch (Fig. 1B), whereas it is more in line with the os exoccipitale in Ilbandornis. (6) The arrangement of the foramina in the basioccipital area is similar in both taxa, but in D. planei, relatively larger mamillar tuberosities are associated with a welldeveloped fossa parabasalis that houses the foramen n. vagi (X), the foramen n. glossopharyngeus (IX), the ostium canalis carotici ventrally, and the ostium canalis opthalmici externi laterally (Fig. 1G). (7) The mamillar tuberosities are larger in D. planei, resulting in the two smaller pairs of insertions caudal to them being less obvious. This appearance is enhanced by the fact that the caudal insertions are not elevated and on each side are conjoined to form a single elongate scar (e.g., NTM P9464-109 and NTM P9464-106), whereas the relatively smaller mamillar tuberosities in Ilbandornis result in better definition of the intermediary insertions of the neck muscles (e.g., m. rectus capitus ventralis; Fig. 1E, F). (8) The insertion for m. pseudotemporalis superficialis forms a less regular and less projecting tuberosity than its counterpart in Ilbandornis. (9) The foramen n. maxillomandibularis is more laterally placed, closer to the base of the processus zygomaticus, and thus is laterad of the insertion for m. pseudotemporalis superficialis rather than ventral to it. (10) The foramen n. oculomotorii (III) is relatively much smaller in size than in Ilbandornis, as best revealed in NTM P9973-6 and P9464109, whereas the foramen n. opticum, and the fossa presphenoidalis are large and obvious. (11) The orbit is much less enclosed laterally by the crista supraorbitalis in D. planei than in Ilbandornis (Fig. 1D, H). Quadrates—Both specimens lack the caudal half of the pars quadratojugalis of the processus lateralis and the processus orbitalis (Fig. 4C, D). As preserved, they are essentially larger versions of the quadrates referred above to Ilbandornis sp., sharing the important features of overall shape and the presence of the foramen pneumaticum rostromediale; however, they have a less projecting condylus pterygoideus. In both fossils, the condylus lateralis is flat but the condylus medialis is noticeably convex ventrally, with its articular surface wrapping onto the medial face. The condylus medialis is more ventrally convex than it is in the Ilbandornis quadrates. They differ from each other slightly by the larger specimen having a more robust tuberculum subcapitulare. Pterygoids—The two better examples, NTM P9464-127 and NTM P9970-1, do not differ greatly in length (53 and 48.5 mm, respectively), but the latter has a much larger facet for the processus basipterygoideus (26 by 18 mm) compared with the former (22 mm by 16 mm), a broader palatine articulation (26 mm vs. 19 mm), and a broader shaft posterior to the facies articularis basipterygoidea (13.3 mm vs. 12.3 mm). They also reveal that this bone is intraspecifically variable in detail, such as the relative length of the shaft caudal to the facet and the width of the palatine articulation relative to the width of the facet, indicating that a much more robust specimen may have similar length. This is to be expected given the extremely foreshortened crania of these birds. These pterygoids are similar to those attributed to Ilbandornis sp., but it is noteworthy that the shaft posterior to the processus basipterygoideus is dorsally flattened to convex and lacks a sulcus, in contrast to the deep sulcus present in those of D. stirtoni. Mandibles—Specimen NTM P9464-112 is the most informative: it and others were described by Murray and Megirian (1998: figs. 11, 12), so only salient points are mentioned here. It displays a short, robust, slightly upturned processus medialis mandibulae with a pneumatic foramen. The cotyla medialis is deeper and slightly shorter than the cotyla lateralis, with a low intervening crista intercotylaris. The cotylae are short, such that the length of either is less that the width across both. In contrast, the cotylae are much more elongate in Ilbandornis sp. and Barawertornis tedfordi. The lateral margin of the cotyla lateralis is markedly angular, in stark contrast to the evenly convex form in Ilbandornis and Barawertornis. It has only a very small fenestra caudalis mandibulae located below the processus coronoideus, above a weakly defined fossa aditus canalis mandibularis. The mandible is very deep, with maximum depth 38% of the length to the cotylae, and the tomial margin is relatively short, being less than half the mandibular length. Also, the processus retroarticularis is very robust, with its depth equal to its caudal extension, as also seen in Barawertornis. DROMORNIS STIRTONI Rich, 1979 Material Crania—NTM P3249, P3250, P3251, P5420, P9342, and P98105 and occipital fragments NTM P98106 and SAM P48643. Quadrates—NTM P3201, left quadrate, height D 64 mm; NTM P3202, left quadrate, essentially complete but lacking part of the pars quadratojugalis and with processus orbitalis distorted by crushing at base, height D 69 mm, width mandibular condyli D 22.6 mm, maximum width capitulum oticum D 19.8 mm (Fig. 4E, F); NTM P5401, right quadrate, lacking part of the pars quadratojugalis and processus orbitalis, height D 52.7 mm, width mandibular condyli D 12.6 mm, maximum width capitulum oticum D 19.1 mm. Worthy et al.—Oligo-Miocene dromornithids (e1031345-11) Pterygoids—NTM P3204, right; NTM P3205, left; NTM P98114, partial left; NTM P98115, partial left. Mandibles—NTM P3241, left side; NTM P3242, right side; NTM P3243, anterior symphyseal fragment; NTM P3244, anterior symphysis; NTM P3245, partial right side; NTM P3246, left side; NTM P3252, part mandible; NTM P98107, left and right sides (Murray and Megirian, 1998:figs. 16, 17; Murray and Vickers-Rich, 2004:figs. 55, 56); NTM P98109, left side and symphysis; NTM P98112, left side and symphysis (Murray and Megirian, 1998:fig 18; Murray and Vickers-Rich, 2004:fig. 56). Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Description Dromornis stirtoni crania were comprehensively described by Murray and Megirian (1998), so only brief pertinent points will be reiterated here. Crania of D. stirtoni attain a larger size (Table 1), but are morphologically very similar to those of D. planei (see Murray and Megirian, 1998); however, because they derive from unconsolidated sediments at Alcoota, they are generally much more poorly preserved. They share all the major features that differentiate crania of D. planei from Ilbandornis: the condylus occipitalis has a constricted neck; in the occipital area, large mamillar tuberosities result in the exits for the cranial nerves and ostia having the same arrangement within a fossa parabasalis; the processus paroccipitalis has a crest anteromedially; the fossa temporalis is deeper, enlarged caudally, and the processus suprameaticus is lateromedially flattened; and the orbits are not deeply enclosed laterally by the crista supraorbitalis. The crania of D. stirtoni mainly differ from those of D. planei by greater development of the ligamental attachment laterally on the cranium dorsal of the cavum tympanicum and have a relatively smaller, rostrocaudally compressed cavum tympanicum, best seen in NTM P5420. The examined specimens vary in the depth of the insertion for the musculi adductor mandibulae externus medialis et superficialis, which is shallow and with two parts in NTM P5420 but deep in NTM P98105. The quadrates are very similar to those of D. planei but differ in two significant ways. First, the medial facies of the pars quadratojugalis is much more excavated into a broad fossa, so accentuating the concave medial facies, and second, there is no foramen pneumaticum rostromediale (Fig. 4F). In addition, the condylus ventralis, although ventrally convex, is less so than in quadrates of D. planei. The pterygoid articulation is revealed as a single facet wrapping from the condylus pterygoideus around a notch onto the base of the processus orbitalis and not as two separate facets. The processus orbitalis in NTM P3202 is short and stout, with a distinct crista orbitalis extending onto the lateral facies (Fig. 4E). The large NTM P3202 has the width of the condylus lateralis relatively increased compared with the smaller NTM P5401 by greater development of a flange projecting ventromedially, likely adding stability to the joint. All the pterygoids of D. stirtoni are damaged to some extent, but those available are similar to those of D. planei in overall morphology. They differ in one major feature: the shaft caudal to the facies articularis basipterygoidea has a deep sulcus dorsally. This feature is obvious in NTM P3205 and is part of the reason why NTM P98115 is referred to D. stirtoni here and not to Ilbandornis sp. (as in Murray and Vickers-Rich; 2004:fig. 143). Additionally, this latter specimen has a relatively large quadratic articulation, about as wide as that in D. planei NTM P9970-1, but much narrower than that of NTM P3240, attributed here to Ilbandornis sp. The mandible of D. stirtoni was described by Murray and Megirian (1998) and Murray and Vickers-Rich (2004) as being very similar to that of D. planei, differing only in attaining larger size, being more gracile, slightly deeper for length, with possibly a shorter symphysis. In addition, there is no fenestra caudalis mandibulae preserved in any specimen, and so this fenestra appears to have been completely closed. DROMORNIS MURRAYI, sp. nov. (Figs. 3C, D, 4A, B, 5A–E, 6A–D, 7A–J) urn:lsid:zoobank.org:act:1085D2C2-5ADD-47C7-86B0-91E245C CCE5C Bullockornis planei Rich, 1979: Boles (1997:242). Unnamed genus and species: Boles (2006:392, table 1). Dromornithidae new genus A sp. 1: Archer et al. (2006:9). Holotype—QM F57984, partial cranium preserving the left side of zona flexoria craniofacialis, the left orbital area and the processus postorbitalis et zygomaticus, the otic regions, the ventral region around the os parasphenoidales, the foramen magnum and surrounding area, and the majority of the neurocranium (Fig. 5). Damage includes erosion to the caudal part of the dorsal surface and loss of the condylus occipitalis, the left processus paroccipitalis, the rostrum parasphenoidalis and its base in the area dorsal to the ostium pharyngeale, the right orbital area, and the processus postorbitalis et zygomaticus. Type Locality—Hiatus A Site (Queensland Museum Locality 941), Hals Hill, D Site Plateau, Riversleigh World Heritage Area, Boodjamulla (Lawn Hill) National Park, northwestern Queensland, Australia (Archer et al., 1989, 1994; Creaser, 1997; Travouillon et al., 2006). Details of the site are available from the University of New South Wales or Queensland Museum on request. Paratypes—From Hiatus Site, Faunal Zone A, Riversleigh: QM F57985, left quadrate lacking processus orbitalis, the caudal margins of the pars quadratojugalis, and the condylus lateralis (Fig. 4A, B); QM F57986, symphysis and left ramus mandible (Fig. 3C, D); QM F45055, right femur, with proximal end incorrectly joined, such that the femoral ball is rotated caudally about 20 from its correct position relative to the shaft. Other sites: QM F57893, right femur, Neville’s Garden Site, Faunal Zone B, Riversleigh World Heritage Area (Fig. 6A–D). Etymology—Named after Peter F. Murray, former Curator of Palaeontology and the Finlayson Vertebrate Collection at the Museum of Central Australia in Alice Springs and co-author of ‘Magnificent Mihirungs, The Colossal Flightless Birds of the Australian Dreamtime.’ Stratigraphy/Age/Fauna—Hiatus Site is a freshwater lacustrine limestone deposit interpreted to be late Oligocene in age (Archer et al., 1997, 2006; Creaser, 1997; Travouillon et al., 2006). The Hiatus Local Fauna has been interpreted as belonging to Faunal Zone A (ibid; Worthy and Scanlon, 2009). Measurements of Holotype—External width between recessus quadratica D 103 mm, length base of foramen magnum to left side zona flexoria craniofacialis D 107.8 mm, width midline to outside processus postorbitalis D 65 mm, therefore maximum width inferred as D 130 mm, width from midline to lateral side of process in fossa temporalis D 58.5 mm, so width between fossa temporalis D 117 mm, maximum diameter orbit D 54 mm, foramen magnum height D 25.5 mm, foramen magnum width at midheight D 20 mm. Measurements of Paratypes—QM F57985, left quadrate, height D 52.2 mm, width mandibular condyli D 14.4 mm, maximum width capitulum oticum D 16.4 mm. QM F57986, left mandible and symphysis, height rostral to cotyla D 58.5 mm, height above ventral angulus D 90 mm (estimated total D 95 mm), width across cotylae D 25 mm, length cotylae D ca. 36 mm, length ventral angle to tip D 233 mm, length cotyla lateralis to tip D 295 mm, length sharp tomial margin D 140 mm. QM F57893, right femur, length D 325 mm, PW D 117 mm, PD D ca. 112 mm, SW D 61.4 mm, SD D 51 mm, DW D 137 mm, depth of condylus medialis 100 mm, depth condylus lateralis D 100 mm. Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-12) FIGURE 5. Dromornis murrayi, n. sp., QMF57984 from Hiatus Site, Riversleigh, Queensland (A–E), in dorsal (A), posterior (B), ventral (D), right ventrolateral (C), and left lateral (E) views. Abbreviations: coe, ostium for canalis opthalmici externi (VI); cs, crista supraorbitalis; ct, cavum tympanicum; ma, insertion area for m. adductor mandibulae externus medialis et superficialis; mt, mamillar tuberosities; po, processus postorbitalis; pp, processus paroccipitalis; ps, processus suprameaticus; pts, insertion for m. pseudotemporalis superficialis; pz, proc. zygomaticus; rq, recessus quadratica; tf, trigeminal foramen or foramen n. maxillomandibularis, for cranial nerves V2 and V3; zfc, zona flexoria craniofacialis; VII, ostium canalis carotici and branch nerve VII; IX, foramen n. glossopharyngeus (IX); X, foramen n. vagi (X); XII, foramina for n. hypoglossi (XII). Scale bar equals 10 cm. QM F45055, right femur, PW D 119 mm, SW D 56 mm, SD D 48.5 mm, PD D ca. 115 mm, width collum 52 mm, caput width 52 mm, depth condylus medialis 100 mm, preserved DW D 135 mm, estimated total DW D 135 mm, preserved length D 330 mm, estimated total length D 360 mm. Referred Material—Hiatus Site, QM L941, Faunal Zone A: QM F57987, badly crushed partial cranium, preserves partial left side and dorsum with processus zygomaticus et postorbitalis and recessus quadratica; QM F57988, rostral fragment mandible symphysis; QM F57989, articular partial left ramus mandible, larger sex; QM F57990, articular partial left side mandible, smaller sex; AM F82182, tip of mandible; QM F57894, proximal left femur, PW D 109.7 mm (on plane bisecting neck), max. PW D 125 mm, SW D 52 mm, PD D 102 mm; QM F57991, shaft left femur, SW D 56 mm, SD D 51.5 mm; QM F57992, shaft left femur, SW D 52.2 mm, SD D 50.7 mm; QM F57993, shaft left femur, SW D 55 mm, SD D 46.8 mm; QM F57994, proximal and shaft right femur; QM F40333, proximal left tibiotarsus; QM F57995, juvenile left tibiotarsus, lacks distal tarsal and supratendinal bridge; QM F57996, shaft left tibiotarsus, min. SW D 52 mm, SD D 40.5 mm; QM F57997, proximal right tibiotarsus, crushed but articular width D 102.6 mm, anterior caudal depth across articular surface D 180 mm; QM F57998, distal left tibiotarsus, min. SW D 64.9 mm, DW D 96.2 mm, depth condylus medialis D 100 mm (Fig. 7D); QM F57999, distal right tibiotarsus, DW D 90.7 mm, depth condylus lateralis D 77.7 mm (Fig. 7E); QM F58000, proximal left tibiotarsus; QM F45053, distal right tarsometatarsus with trochleae metatarsi II, III, and IV, DW D ca. 105 mm, width trochlea metatarsi III D ca. 45 mm; QM F45117, proximal left tarsometatarsus, PW D ca. 105 mm, PD D ca. 78 mm (Fig. 7A); QM F45223, proximal right tarsometatarsus, PW D ca. 93 mm, PD D ca. 75 mm (Fig. 7B); QM F45441, left tarsometatarsus missing trochlea metatarsi IV, L D 404, PW D 102 mm, least SW D 47 mm; QM F58001, juvenile distal left tarsometatarsus, SW D 52 mm, SD D 33 mm, TII–TIII D 66 mm (Fig. 7L); QM F58002, distal left tarsometatarsus with trochleae complete, minimum SW D 44 mm, DW D 97.9 mm, width trochlea metatarsi III D 45.3 mm, depth trochlea metatarsi III D 52.5 mm (Fig. 7C); QM F58007, right scapulocoracoid, total length 120 mm, sternal articular width 36 mm, length pars coracoid 82 mm, length pars scapulae 122 mm (Fig. 7G); QM F58005, anterior part sternum, sulci coracoidei 90 mm apart; QM F58004, proximal left carpometacarpus, preserved PW D 18.4 mm, PD D 10.9 mm (Fig. 7I, J); QM F58006, right humerus, two fragments with bit of shaft missing, PW D 25.2 mm, greatest PD D 17.2 mm, SW D 13.6 mm, SD D 9.7 mm, greatest DW D 21.5 mm, greatest distal depth 13.8 mm (Fig. 7F); QM F58004, atlas vertebra, missing arcus atlantis; QM F58008, dorsal vertebra; QM F58009, dorsal vertebra; QM F58010, cervical vertebra; QM F58011, cervical vertebra; QM F58012, cervical vertebra. Burnt Offering Site, D-Site Plateau, Burnt Offering LF, Faunal Zone A, Riversleigh World Heritage Area: QM F57896, nearly complete sternum. White Hunter Site, Hals Hill, White Hunter LF, Faunal Zone A, Riversleigh World Heritage Area: QM F30826, distal left Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-13) FIGURE 6. The paratype femur of Dromornis murrayi, n. sp., QM F57893 from Neville’s Garden, Riversleigh, in caudal (A), lateral (B), cranial (C), and caudolateral (D) views. D is coated with ammonium chloride. Abbreviations: c, collum femoris; cai, caudal impressio for ansa m. iliofibularis; cf, caput femoris; cl, condylus lateralis; cm, condylus medialis; ct, crista tibiofibularis; fa, facies antitrochanterica; fp, fossa poplitea; ftt, fovea tendineus m. tibialis cranialis; iie, insertion for m. iliotrochantericus cranialis; iim, insertion for m. iliotrochantericus medialis; ilcc, impressio ligamentum cruciati cranialis; ilic, linea intermuscularis caudalis; img, insertion for m. gastrocnemialis; iol, insertion for m. obturatorius lateralis and obturatorius medialis; iom, insertion for major part m. obturatorius lateralis; lcc, impressio ligamentum cruciati caudali; lic, linea intermuscularis caudalis; licr, linea intermuscularis cranialis; pai, cranial impressio for ansa m. iliofibularis; pf, pretrochanteric facies; sp, sulcus patellaris; tf, trochanter femoris; tfib, trochlea fibularis. Scale bar equals 10 cm. tarsometatarsus DW D 101.6 mm, width trochlea metatarsi III D 46.5 mm. Diagnosis—Cranium as for Dromornis planei, but the mamillar tuberosities are considerably smaller, narrower, and less prominent ventrally (Fig. 5B, D); the ridges extending from the mamillar tuberosities to the condylus occipitalis are less robust, so that the foramina in the basioccipital area open onto a shallow concave facies lacking a discrete fossa parabasalis (Fig. 5B); the processus suprameaticus is flattened (Fig. 5C), but more robust than in D. planei; the fossa temporalis is shallowly excavated Worthy et al.—Oligo-Miocene dromornithids (e1031345-14) dorsal to the cavum tympanicum but not excavated dorsal to the recessus quadratica (Fig. 5C, E); the fossa for the musculi adductor mandibulae externus medialis et superficialis is large and extends medially rostral to the insertion for m. pseudotemporalis superficialis (Fig. 5C, D), the latter is a conical tuberosity as in Ilbandornis. The quadrate has (1) a foramen pneumaticum rostromediale, (2) a medial facies that is shallowly concave in the area rostral to the pars quadratojugalis, and (3) a very low tuberculum subcapitulare (Fig. 4A, B). The femur has the same shape as that of Dromornis planei, but is smaller (Fig. 6). Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Description and Comparisons Cranium—The cranium QM F57984 of Dromornis murrayi, n. sp. (Fig. 5), shares with D. planei and D. stirtoni the following features: the processus paroccipitalis has a compressed flange on its anteromedial margin (lacking in I. woodburnei); the same arrangement of the foramina in the basioccipital area; a rectangular foramen magnum with a flat dorsal margin (markedly convex dorsally in I. woodburnei); the same shape and orientation of the cavum tympanicum; the dorsal parts of the orbits are little enclosed laterally (well enclosed in I. woodburnei), resulting in the maximal width of the cranium being across the processus postorbitalis (across the dorsal parts of the orbits in I. woodburnei); and a much reduced foramen n. oculomotorii (III) compared with I. woodburnei. Although of similar size (Table 1), it differs from crania of D. planei and D. stirtoni in that the foramen n. vagi (X), the foramen n. glossopharyngeus (IX), the ostium canalis carotici, and the ostium canalis opthalmici externi are not enclosed in a welldeveloped fossa parabasalis as in those taxa (Fig. 5B). The processus suprameaticus (Fig. 5C, E) is much more reduced than it is in Ilbandornis species, but not to the thin flattened sliver seen in D. planei and D. stirtoni. The fossa temporalis is much shallower, with little excavation dorsal to the recessus quadratica and the cavum tympanicum (Fig. 5C, E). The fossa for the musculi adductor mandibulae externus medialis et superficialis is larger than that in D. planei and Ilbandornis species (Fig. 5D); in these taxa it does not extend medially along the rostral side of the insertion for m. pseudotemporalis superficialis. Although this fossa passes rostromesad of the insertion for m. pseudotemporalis superficialis in D. stirtoni, it is shallower and not so defined rostrally. The foramen n. maxillomandibularis is located ventral to the insertion for m. pseudotemporalis superficialis and at the same separation from the midline, as in Ilbandornis woodburnei and D. stirtoni, rather than more laterad as in D. planei. Quadrate—One specimen (QM F57985) is available for study (Fig. 4A, B). It is of similar size to NTM P9464-118 of D. planei from Bullock Creek and likewise has a foramen pneumaticum rostromediale. It differs from those of D. planei in having a less concave medial facies in the area rostral to the pars quadratojugalis, in lacking a tuberculum subcapitulare, and the condylus medialis is less convex ventrally (Fig. 4). The capitulum oticum et squamosum is also more globose than D. planei NTM P9464118, which is more compressed rostrocaudally; however, the Hiatus specimen is similar to the D. planei specimen NTM P9464100, so the relative globoseness of the capitulum appears to be variable. As in D. planei, the pterygoid articulation is a single facet wrapping from the condylus ptergoideus around a notch onto the base of the processus orbitalis. Specimen QM F57985 thus forms the oldest and least derived end of a sequence of quadrates (Dromornis murrayi, n. sp.—D. planei—D. stirtoni) marked by increased concavity of the medial facies and increased size of the tuberculum subcapitulare in younger forms, and between D. planei and D. stirtoni, loss of the foramen pneumaticum rostromediale. Mandibles—Of the several fragments of mandibles available, QM F57986 is the most informative, despite some crushing that most affects the medial side and having an incomplete coronoid margin (Fig. 3C, D). It is relatively shallower compared with length than are those of Ilbandornis species (NTM P2774-2) and other Dromornis species. For example, the length cotyla lateralis to tip (295 mm) is 3.1 times the estimated maximum depth of 95 mm, compared with equivalent ratios of 2.65 (D. planei; NTM P9464-112) and 2.35 (D. stirtoni; NTM P98107); a similar ratio for Ilbandornis species cannot be computed because the mandible tip is missing on the most complete specimen (NTM P27742), yet the attenuation of height proximal to the processus coronoideus suggests a relatively short deep mandible. A large part of the loss of depth in the new species is because the mandible has minimal ventral projection in the region just anterior to the cotylae, so that along the length of the mandible it is relatively flatter ventrally than those of other species that can be compared. Despite damage obliterating a section of the mandible extending from the processus coronoideus caudoventrally to just below mid-depth rostral to the cotylae, it is apparent that the specimen cannot have had a large fenestra caudalis mandibulae situated above mid-depth and extending rostrally of the processus coronoideus, as is the case in Ilbandornis species. The new species is like D. planei in having at most a small fenestra caudalis mandibulae. Like all dromornithids, a short, mediolaterally thick, and deep processus retroarticularis is present, but the extent of dorsal upturning, if any, cannot be ascertained due to damage. Damage medially prohibits any assessment of the fossa aditus canalis mandibularis. Specimen QM F57989 is a caudal fragment of a mandible and the bone mass joined anterior to the cotyla is likely not of the mandible, or if it is, it has been displaced from its original position. The specimen has a ridge extending ventrorostrally from the cotylae along the medial aspect that is the end of the fossa aditus canalis mandibularis. The depths of the three specimens at the rostral side of the cotyla (QM F57989, 63 mm; QM F57986, 58.5 mm; QM F57990, 50 mm) also reflect the marked size variation exhibited by femora in the sample. This similar to that seen in D. planei and D. stirtoni and likely reflects sexual dimorphism. Femora—The femur QM F57893 from Neville’s Garden is the best example (Fig. 6), and its morphology does not differ from the Hiatus Site material. Together they show that femora of Dromornis murrayi, n. sp., with a range in SW of 52–61 mm (n D 6; see Measurements in Referred Material above), overlaps in size with D. planei (e.g., QMV:2000:GFV:456, with SW D 59 mm, or QMV:2000:GFV:417, with SW D 60 mm), but none are as large as D. planei NTM P9464-193, which has a minimum SW D 73 mm. Moreover, femora of D. murrayi, n. sp., are much smaller than those of D. stirtoni. If the cranium QM F57984 is from one of the birds represented by femora from Hiatus Site, then it appears that D. murrayi had relatively smaller legs compared to cranium size in other, later occurring species. Given the large size variation in Dromornis species and lack of associated bones of individuals, more complete and associated materials are necessary to verify this assertion. The femur is described here in detail because this element is the holotype for several other dromornithids and QM F57893 is far better preserved than any previously described type material of the group. The femur is robust, wider at midlength than deep, with the shaft, and particularly the caudal facies, straight in lateral view, and the medial facies evenly concave in caudal view. The trochanter femoris is (1) short, with a length less than twice the proximodistal width of the caput femoris; (2) robust or mediolaterally thick and elevated cranially such that its craniocaudal depth is about twice that of the caput; and (3) projects proximally only slightly more so than the caput from which it is separated by a broad ‘U’-shaped notch. The collum femoris is not constricted in proximal view. The caput shows little medial projection from the shaft (Fig. 6A). The facies antitrochanterica is concave in the mediolateral plane (Fig. 6A). The pretrochanteric facies is flat Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-15) and lacks pneumatic foramina (Fig. 6C). A crista linking the caput and the trochanter femoris along the caudal side of the facies antitrochanterica markedly overhangs the caudal facies (Fig. 6B). Cranially, a linea intermuscularis cranialis extends proximally from the lateral side at about the middle of the shaft to pass medially of the distal end of the trochanter and along the pretrochanteric facies (Fig. 6C). An elevated slightly rugose area spreading over the caudolateral margin just distal to the facies antitrochanterica represents the likely area of the insertion for the mm. obturatorii lateralis et medialis (Fig. 6B, D). The insertion area for the major part of m. obturatorius lateralis, forms a distinct bulge 28 mm long traversing the caudolateral margin about 35 mm further distally of a smooth concave intervening zone (Fig. 6B, D). Towards the cranial facies from this obturator impression, there is a marked rugosity, about 28 mm from the trochanter femoris, some 17 mm long and 20 mm wide, interpreted as the insertion area for the m. iliotrochantericus cranialis (Fig. 6B). A smaller rugose zone closer to the end of the trochanter is presumed to be the insertion area for m. iliotrochantericus medialis. As in all dromornithids, the linea intermuscularis caudalis forms an elongate elevation on the medial side of the shaft just distal to midlength (Fig. 6A, D). A small nutrient foramen is located at about midlength on the medial facies about 10 mm from the linea. The fossa poplitea is large, deep, and contains two large pneumatic foramina, one extending along the distal margin of the fossa and the other large and just proximal to an elongate insertion area for ligamentum cruciati caudali that traverses the fossa (Fig. 6A). The impressio ligamentum cruciati cranialis is shallow and only slightly deepened into the base of condylus medialis but not into the condylus lateralis (Fig. 6A). The crista tibiofibularis is robust, oval to elongate triangular in caudal view, with its lateral facies flat and arising from the trochlea fibularis at right angles (Fig. 6A). The trochlea fibularis projects 22 mm from the condyle and is more than two-thirds the width of the crista tibiofibularis. Its articular facet is slightly convex caudally in lateral view, and it terminates abruptly distally so that in caudal view it meets the condylus lateralis at a marked angle proximal to the distal extreme of that condyle (Fig. 6). The caudal impressio ansa m. iliofibularis forms an elongate rugose scar aligned mediolaterally and extending proximomedially from the lateral margin just proximal to the trochlea fibularis (Fig. 6D). It merges with a similarly elongate scar for the insertion of m. gastrocnemialis that is aligned at right angles to the crista tibiofibularis. The cranial impressio ansa m. iliofibularis is a 12-mm-long scar about 36 mm proximal to its caudal counterpart just below mid-depth on the lateral facies (Fig. 6D). The fovea tendineus m. tibialis cranialis forms a distinct depression distally on the condylus lateralis at a craniocaudal depth level with the sulcus patellaris (Fig. 6C). The condylus medialis in caudal view projects medially and in medial view projects caudally from the shaft. There is no sharp crista supracondylaris medialis. The sulcus patellaris is broad and flat, with the condyles elevated only about 15 mm above it. The crest of the condylus lateralis in cranial view deviates from the axis by about 30 and is parallel to the condylus medialis. In cranial view, the distal end between the condyles is broadly and shallowly concave. No substantive femoral differences were found, other than size, to separate the new species from D. planei. However, Rich (1979) listed a constricted collum as a feature of D. planei and D. stirtoni, whereas in the new species the collum is only marginally (QM F57893) or not (QM F45055) constricted in proximal view. The extent to which this feature is affected by individual variation will remain to be seen in larger samples. Femora of D. stirtoni are larger and considerably more robust, with much enlarged distal and proximal ends relative to length, resulting in the medial shaft facies in caudal view being highly concave. The holotype AM F10950 of Dromornis australis, the type species of the genus, is damaged, limiting possible comparisons. The trochanter femoris is broken both cranially and proximally, precluding determining its original relative proximal extent; however, at least another 10 mm was likely present proximally. The cranial surface between the trochanter femoris and the collum femoris is crushed. The caput is eroded, with perhaps 10 mm of the medial facies missing. Distally, all of the craniodistal part of condylus lateralis and the cranial part of the condylus medialis are broken and no original intercondylar area is preserved distally. The trochlea fibularis is badly damaged, as is also the crista tibiofibularis, precluding interpreting the original form of the trochlea fibularis. The linea intermuscularis caudalis forms an elongate elevation on the medial side of the shaft just distal to midlength. The insertion for m. gastrocnemialis is elongate and shallow, but its continuation medially as the caudal impressio ansa m. iliofibularis is lost. In caudal aspect, the condylus medialis is complete proximally and the adjacent medial facies is separated from the fossa popliteus by a broad, rounded ridge. As preserved, AM F10950 shows that the trochanter was robust and its distal extent was very short, as in other dromornithids. The impressiones obturatoriae are low, and weakly marked. The linea intermuscularis caudalis is weakly expressed. The facies articularis antitrochanterica overhangs the caudal facies. A small nutrient foramen is located at midlength on the caudal facies about 10 mm from the medial margin. The distal condyles are broadly separated by a shallow flat sulcus patellaris. The bone near the collum femoris, especially caudally under the caput and on the lateral facies adjacent to the trochanter femoris, has a lineated texture that suggests that the fossil is of a juvenile. There are also no preserved ligamentous attachment sites apparent in this area. This juvenile nature is obvious in the illustrations in Owen (1873, 1879). Despite this juvenile status and damage, the unique holotype of D. australis differs from the new species as follows: in lateral view, the caudal facies is concave, rather than straight; the shaft appears to have a slight dorsoventral curvature and is not flattened caudally at midlength, so its section is more oval as originally noted by Owen (1873, 1879); the collum femoris is constricted in proximal view; the cranial projection of the trochanter femoris is less than the craniocaudal width of the caput; and the condylus medialis is not as projecting medially. Femora of the new species differ markedly from those of Genyornis, the latter of which has greatly enlarged proximal and distal ends. This results in increased concavity of both the medial and lateral sides, a more proximally projecting trochanter femoris, a broader shaft, more medially projecting condylus medialis, and a deeper ‘U’-shaped sulcus patellaris (Stirling and Zietz, 1900; Murray and Vickers-Rich, 2004). The new species has femora markedly larger than those of Barawertornis and Ilbandornis species (Rich, 1979; Nguyen et al., 2010; Worthy and Yates, 2015). Tibiotarsi—The few tibiotarsi available (Fig. 7D, E) are generally smaller than those of Dromornis planei, as expected from the size of femora. There are no significant differences between the distal right tibiotarsus of D. planei NTM P9464-203 and those of the new species. All share a centrally placed sulcus extensorius, the condylus medialis is not displaced medially in the manner of anseriforms, and the pons supratendineus is longer than wide and aligned transversely across the shaft (not at right angles as in anseriforms). The condylus medialis projects anteriorly beyond the condylus lateralis. The distal attachment for the retinaculum extensorium tibiotarsi (lig. transversum) is an elongate rugosity lateral to the pons supratendineus. This is aligned from a medial location distal to the pons proximolaterally to a point near the lateral margin at about midlength of the pons. Laterally, there is a shallow depressio epicondylaris lateralis. Medially, the epicondylaris medialis is low and not prominent and has a distinct depressio epicondylaris medialis anterior to it. The distal condyles are not separated anteriorly by an incisura intercondylaris. Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-16) Tarsometatarsi—The tarsometatarsi referred to Dromornis murrayi, n. sp., are smaller, with length D 102 mm, proximal width D 93–105 mm, and distal width D 98–105 mm, than those of D. planei, but much larger than those of Barawertornis tedfordi (see Nguyen et al., 2010). The eminentia intercotylaris projects proximally of the area intercotylaris and the cotylae, but in proximal view it does not exceed the cotylae anteriorly (Fig. 7A, B). The hypotarsus comprises a single ridge as for all dromornithids, and there is minimal development of fossae parahypotarsalis medialis et lateralis. The tarsometatarsi share with D. planei, e.g., NTM P9464-210, a much reduced foramen vasculare distale, a dorsally open canalis interosseous distalis, trochleae metatarsi II and IV that lack a medial groove, and a similar pattern of distal projection of the trochleae, with trochlea metatarsi III greatest and trochlea metatarsi II least (Fig. 7C). However, the distal fragments referred to the new species differ from D. planei NTM P9464-210 by a less expanded distal end (e.g., the DW:SW ratio is 2.22 in QM F58002 versus minimally 2.5 in NTM P9464-210) that does not reveal the minimum shaft width and DW is compromised by loss of a sliver of trochlea metatarsi II. Related to this difference in relative distal width is the observation that the trochleae are not so greatly splayed as in NTM P9464-210, where trochleae metatarsi II and IV are more widely separated (Fig. 7C, H). Sternum—The nearly complete sternum QM F57896 is of appropriate size for D. murrayi and matches QM F58005 from Hiatus Site described below. Measurements: width at anterior processus costales approximately 219 mm (surface missing on left); midline length 157 mm (margin caudally eroded); distance between coracoidal sulci is 84 mm. It is acarinate, as are all dromornithids, wider than long, with a flattened central section flanked by slightly upturned sides. The processus craniolateralis projects cranially, but not laterally, of the sulcus articularis coracoideus by about 40 mm. The sulci articularis coracoidei are, like other dromornithids, widely separated and essentially abutments medial to the processus craniolateralis and the cranial margin is notched between them. There are four processus costales of which the last is about 30 mm from the caudolateral end: there is no distinct trabecula lateralis. The trabecula medialis is separated by a shallow notch from the lateral margin and projects further caudally than the caudolateral corner. The sternal fragment QM F58005 is slightly larger, with the sulci articularis coracoidei separated by 90 mm. These specimens have the sulci more widely separated than in NTM P3262, a sternum attributed to Ilbandornis species from Alcoota (75 mm), and further differ from that specimen in having the coracoidal sulci directed more cranially, not craniolaterally. Specimen NTM P3262 is also longer than wide and lacks processus craniolateralis. The two referred sterna are slightly smaller than smaller Dromornis stirtoni sterna (e.g., NTM P9310) where the sulci are 105 mm apart, but share the more cranially directed sulci and markedly cranially projecting processus craniolateralis, supporting their attribution to Dromornis. A low median ridge dorsally separates the basin into left and right halves, at least anteriorly, and is more accentuated than that seen in some sterna of D. stirtoni (e.g., NTM P6005). The anterior profile between the sulci articularis coracoidei is more deeply concave than in all D. stirtoni sterna, wherein this feature varies from concave to flat. Scapulocoracoid—The right scapulocoracoid QM F58007 (Fig. 7G) is typical of dromornithids (e.g., that of D. stirtoni; see Murray and Vickers-Rich, 2004). The pars coracoideus is fused to the pars scapularis, the latter of which is about 1.5 times longer. The junction is marked by a deep glenoid sulcus for the humeral articulation. The pars coracoid has no evidence of an incisura nervi supracoracoidei; sternally it lacks a discrete articular facet for sternal articulation, although it is much thicker dorsomedially than it is laterally, and it does have pneumatic foramina penetrating the impressio m. sternocoracoidei. The width of the pars scapula attenuates distally except for a slight expansion at the distal extreme. Medially, a projection on the pars scapula opposite the glenoid sulcus may be a fused os claviculae or, more probably, a rugose attachment point for the membrana sternocoracoclavicularis. This specimen is smaller than those attributed to Ilbandornis species from Alcoota (e.g., NTM P3291 and P3292) but because it fits into the sulci of the sternal fragment QM F58005, it is of appropriate size for Dromornis murrayi, n. sp. Humerus—The two fragments of one right humerus (QM F58006) indicate that this element was already markedly vestigial in this dromornithid lineage by the early Miocene (Fig. 7F). There is no indication of a fossa pneumotricipitalis, the caput humeri is obsolete, and the crista deltopectoralis is robust and only in its distal part does it thin to a crest as it joins the shaft. The tuberculum ventrale is a low, rounded rugose surface that marks the craniocaudally deepest part of the bone, and there is no sign of a crista bicipitalis. The attachment of m. latissimus dorsi is the most notable muscle or ligament attachment in dromornithid humeri (Murray and Vickers-Rich, 2004). In this specimen, it is an elongate sulcus on the caudal surface close to the dorsal margin, extending from level with the end of the crista deltopectoralis for 12 mm distally. Distally, there are no condyles, just a single articular surface directed distally, which is craniocaudally deepest dorsally. In humeri of D. stirtoni there is considerable variation in the detailed shapes of the proximal and distal ends. The humerus of the new species does not differ significantly from them. Carpometacarpus—The proximal left carpometacarpus QM F58003 (Fig. 7I, J) reveals that Dromornis murrayi, n. sp., shared a similar highly modified carpometacarpus to those reported for other dromornithids (e.g., D. stirtoni, D. planei, and Genyornis newtoni; Rich, 1979; Murray and Vickers-Rich, 2004). Like in all these species, there is no trochlea carpalis: rather, the proximal end has flattened articular surfaces for the ulna and radius. The os metacarpale majus is fused to a hollow bone for 16.5 mm, although a foramen passes through the synostosis at about half this distance. Because the proximal articulation on this smaller fused element is about half the diameter of that on the os metacarpale majus, it follows that it is for the radius in which the articular surface is much smaller than that of the ulna. Therefore, this structure on the side of the os metacarpale majus is the processus extensorius (metacarpal I) with the os metacarpale alulae fused to it distally (Fig. 7I, J). The os metacarpale majus is about 10 mm in diameter at the preserved distal end. This breakage occurred proximal to the origin of os metacarpale minus, which in D. stirtoni and D. planei is seen as a relatively narrow ridge conjoined to the os metacarpale majus and extending distally to sometimes protrude as a discrete element (Murray and Vickers-Rich, 2004). Vertebrae—The atlas vertebra is represented by QM F58004. The facies articularis axialis is 26.4 mm wide and 17.4 mm high medially, and the corpus atlantis is 19.8 mm long. There is no evidence of foramina transversaria. Specimen QM F58008 is a dorsal vertebra that is last in the presacral series, with a total height of 185 mm, centrum length of 46 mm, and depth below foramen vertebrale anteriorly of 54 mm. The processus spinosus is very tall and much wider (49.6 mm) than long (34 mm) at midheight. A low processus ventralis is present anteriorly, but the ventral profile is flat. Large pneumatic foramina penetrate the corpus vertebrae laterally just above and just below the foramen vertebrale and anteriorly on the neural platform (recessus dorsocraniales pneumatici). Specimen QM F58009 is a dorsal vertebra that is second to last in the presacral series and articulates directly with QM F58008. It has a total height of 182 mm, centrum length of 50 mm, and a depth below foramen vertebrale anteriorly of 46 mm. The processus spinosus is very tall and much wider (40 mm) than long (30 mm) at mid height. It is similar to QM F58008 in most features but has a more prominent processus ventralis. Together Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-17) FIGURE 7. Postcranial elements of Dromornis murrayi, n. sp., from Hiatus Site, Riversleigh. Proximal left tarsometatarsus QM F45117 in plantar view (A); proximal right tarsometatarsus QM F45223 in proximal view (B); distal left tarsometatarsus QM F58002 in dorsal view (C); distal left tibiotarsus QM F57998 in anterior view (D); distal right tibiotarsus QM F57999 in anterior view (E); right humerus in two non-joining pieces QM F58006 in caudal view (F); right scapulocoracoid QM F58007 in caudodorsal view (G); left tarsometatarsus QM F45441 in dorsal view (H); proximal left carpometacarpus QM F58003 in dorsal (I) and ventral (J) views. Abbreviations: cl, cotyla lateralis; cm, cotyla medialis; col, condylus lateralis; com, condylus medialis; dre, distal attachment for the retinaculum extensorium tibiotarsi (lig. transversum); ei, eminentia intercotylaris; fvd, foramen vasculare distale; oma, os metacarpale alulae; omm, os metacarpale majus; pc, pars coracoideus; pons, pons supratendineus; ps, pars scapularis; rua, articular facet for radius and ulna; se, sulcus extensorius; TII, trochlea metatarsi II; TIV, trochlea metatarsi IV. Scale bars equal 50 mm (A–H) and 10 mm (I and J). these thoracic vertebrae indicate that the ilia extended high above the synsacrum in the pelvis. A well-preserved cervical vertebra, QM F58011, is missing the zygopophyses craniales and the right ansa costotransversaria. It is similar to Vertebra A of Genyornis newtoni (see Stirling and Zietz, 1905), with the zygopophyses caudalis separated by narrow parallel-sided area lig. elastici and a thin and narrow lamina arcocostalis that dorsally encloses a foramen arcocostalis cranialis that lies dorsal to the foramen vertebrale. It differs by a smaller foramen transversarium and in facies articularis cranialis being more sloped dorsoventrally, indicating that this is a relatively cranial vertebra, perhaps 5 or 6, where the neck is curving from horizontal to vertical in normal stance. The centrum length is 76 mm. Specimen QM F58010 is a well-preserved midcervical vertebra, although with some erosion to both ansa costotransversaria and both zygopophyses caudalis. It is similar to vertebra C of Genyornis newtoni (see Stirling and Zietz, 1905), with zygopophyses caudalis being somewhat divergent caudally, the area lig. elastici shorter and deeper, the recessus dorsocraniales deeper and defined by steeper walls caudally, and the facies articularis cranialis at right angles relative to the Worthy et al.—Oligo-Miocene dromornithids (e1031345-18) centrum than in QM F58011. As such, it was likely more caudal in the vertebral series. The centrum length is 66 mm. Specimen QM F58012 is a more caudally positioned cervical vertebra than the previous two, one from near the apex of the neck loop as indicated by well-developed processus carotici that even though damaged, indicate that they nearly enclosed the carotid artery. The centrum length is 74 mm. Together these cervical vertebrae indicate a robust and relatively short neck in Dromornis, because none of the vertebrae are elongated as seen, for example, in Dromaius or further accentuated in Struthio. Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 BARAWERTORNIS TEDFORDI Rich, 1979 Barawertornis tedfordi is a small dromornithid found in multiple local faunas from Faunal Zones A and B at Riversleigh in Northwest Queensland from the late Oligocene to early Miocene (Nguyen et al., 2010). To date, no skull material has been described. Material Cranial—QM F58013, Hiatus Site, QM L941, Faunal Zone A, Riversleigh, posterior right lateral fragment of cranium (Fig. 2E, F). Pterygoid—QM F24124, Hiatus Site, QM L941, Faunal Zone A, Riversleigh, right, total length 33 mm, height at caudal end facies articularis basipterygoidea 12.9 mm. It lacks the medial side of the facies articularis basipterygoidea and palatine articulation. Mandible—QM F57895, Neville’s Garden, Faunal Zone B, Riversleigh, left and right sides of a mandible (Fig. 3E–G). Postcranial—QM F58014, distal left femur; QM F58015, thoracic vertebra. process is similar to but proportionally less projecting than that seen in D. planei NTM P9970-1. Mandible—The mandible QM F57895 was preserved with its symphysis a little crushed so that the rami lay parallel to each other (Fig. 3E–G). Erosion had differentially removed bone, producing voids that were filled with resin before acid etching of the specimen from the enclosing limestone. The right side lacks the posterior half of the processus retroarticularis and the dorsal half of the ramus from anterior to the angulus mandibulae to the symphysis, but the entire ventral margin and area caudad of the angulus mandibularis are otherwise well preserved. The left side complements the right side by preservation of the dorsal and ventral margins of the ramus rostral to the angulus mandibularis and more of the processus retroarticularis, but its caudal end is also broken. Measurements: QM F57895 has a preserved length of 210 mm (left side), but a bit of the rostral tip and tip of this processus retroarticularis are missing, so a former length of 220 mm is estimated. The height at processus coronoideus D 52 mm, the length processus coronoideus to anterior side cotylae is 42 mm, the width across cotylae is 15.3 mm, and the length cotyla lateralis is 21 mm. In form it is very similar to the mandible of Ilbandornis (NTM P2774-2) described above except that it differs by lacking a fenestra caudalis mandibulae (Fig. 3G). The complete processus medialis mandibularis has a pneumatic foramen, is short, robust, and upturned dorsally (Fig. 3E). The processus retroarticularis on the left side is best preserved: it is deep and robust, with its ventral margin upturned before the breakage zone, suggesting that its total length was less than that of the cotylae. As preserved, the processus retroarticularis lacks dorsal extension above the cotylae, and given the size of the tip as preserved, any dorsal extension was minimal (Fig. 3E–G). DISCUSSION Description Crania—The only cranial fragment known is QM F58013, a right caudolateral section of a cranium (Fig. 2E, F). At 34 mm from the caudal angle of the os exoccipitale to the anterior side of the recessus quadratica, it is much smaller than Ilbandornis QVM:2000:GFV:20 (47 mm) and thus is of the expected size for B. tedfordi, given the smaller size of the leg bones of this species (see Nguyen et al., 2010). The morphology is very similar to that of Ilbandornis woodburnei: the foramen magnum is similarly tall and narrow, the foramina for nerves and other ostia in the occipital area have the same arrangement, laterally the fossa temporalis is similarly shallow, a robust conical processus suprameaticus is present, and the insertion for m. pseudotemporalis superficialis is conical and projecting. Apart from its smaller size, the only significant difference is that in the cranium of B. tedfordi the insertion for the musculi adductor mandibulae externus medialis et superficialis has two distinct parts, a deeper fossa adjacent to the base of the processus zygomaticus and arcing around this medially a shallower one. There are no differences between these fossils that would warrant generic distinction, and Barawertornis could easily be accommodated as the smaller and older progenitor of Ilbandornis species. Pterygoid—A well-preserved right pterygoid (QM F24124) is also from Hiatus Site at Riversleigh and is referred to B. tedfordi on the basis of its small size. This specimen is smaller than NTM P9973-8 from the larger Ilbandornis sp. in the Bullock Creek LF. It is smaller, but does not differ substantially from those referred to Ilbandornis or Dromornis; see Murray and Vickers-Rich (2004:fig. 94). It is similar to those of D. planei in that the dorsomedial surface of the shaft caudal to the facies articularis basipterygoidea is flattened to convex and lacks a fossa. The specimen preserves an elongate dorsal process extending about 6 mm above the quadrate articulation, for a total of 13.6 mm. This In this contribution, the skull anatomy of dromornithids from the late Oligocene to the late Miocene is described, with a focus on crania, mandibles, quadrates, and pterygoids. The new material includes the first well-preserved cranium of a species of Ilbandornis, which derives from the middle Miocene Bullock Creek (ca. 12 Ma) and is referred to I. woodburnei. A cranial fragment, a quadrate, and a pterygoid from Riversleigh local faunas of late Oligocene to early Miocene age (25–17 Ma) are referred to Barawertornis tedfordi and enable comparisons with cranial material of species of Ilbandornis. The well-preserved crania, pterygoids, and quadrates and mandibles of Dromornis planei from Bullock Creek LF are redescribed and compared with those of species of Ilbandornis and D. stirtoni. Lastly, a new species, Dromornis murrayi, n. sp., is described based on partial crania, a quadrate, mandibles, and some postcranial elements from sites attributed to Faunal Zones A and B of late Oligocene to early Miocene age (25–17 Ma) from Riversleigh World Heritage Area, Queensland. All dromornithids are characterized by crania that are extremely foreshortened, with the zona flexoria craniofacialis transecting part of the orbit, and their depth considerably greater than rostrocaudal length. However, this morphology reaches its greatest manifestation in D. stirtoni, where rostrocaudal length is about half the depth of the crania. The Dromornis lineage also exhibits concomitant trends in quadrate morphology associated with increased skull size, an increased concavity of the medial facies, increased size of the tuberculum subcapitulare, a flattening of the condylar articulation with the mandible, and between D. planei and D. stirtoni, in the loss of the foramen pneumaticum rostromediale. At the same time, the mandibles show a trend over time towards loss of the fenestra caudalis mandibulae and increased depth of the mandible. The latter probably implies that the premaxilla also increased in depth as Dromornis species Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-19) got bigger. Despite the large bills, the fossa temporalis is exceedingly small in part due to the rostrocaudal compression of the crania. The loss of the area of attachment for the mandibular muscles associated with this autapomorphic foreshortening of the cranium is somewhat offset by enlarged insertion areas on the quadrate associated with the increased medial concavity of that bone and by the presence of large distinct fossae at the base of the processus zygomaticus for the musculi adductor mandibulae externus medialis et superficialis. An origin of musculi adductor mandibulae externus medialis et superficialis on the quadrate has been recognized in some galliform and anseriform birds (Holliday and Witmer, 2007; Lautenschlager et al., 2014), so it may be a trait of Galloanseres. Even so, the muscle mass available to operate the large bills of these birds is surprisingly limited and prohibits the ability for forceful biting required for a fibrous diet, such as the twig dominated diet of Dinornis moa (Worthy and Holdaway, 2002). Bearing on the hypothesis of a weak biting ability for these birds is that their upper bills are very fragile and thinly constructed, which contributes to their rarity and fragmentary nature in the fossil record (Murray and Vickers-Rich, 2004). The near-complete cranium here referred to I. woodburnei reveals a typical dromornithid structure. It makes it most unlikely that the skull referred to Ilbandornis woodburnei by Murray and Vickers-Rich (2004:111–112, figs. 91, 92) from the Alcoota LF originally had a supraoccipital area that markedly caudally overhung the foramen magnum; instead, the structure on NTM P9843 is interpreted as an artifact of preservation. The cranial material referred to species of Ilbandornis differs from that of species of Dromornis as follows: (1) the orbit is relatively larger and more enclosed laterally; (2) the foramen n. maxillomandibularis is positioned further mesad of the base of the processus zygomaticus and ventral to the insertion for m. pseudotemporalis superficialis; (3) the foramen n. oculomotorii (III) is relatively larger; (4) the processus suprameaticus is more robust and conical; (5) the quadrates have a more projecting condylus pterygoideus but are otherwise similar to those of the smaller species of Dromornis; and (5) on the mandible, the cotylae are more elongate, the lateral margin of the cotyla lateralis is evenly convex, and the fenestra caudalis mandibulae is large. In addition, there are relative differences in expression of structures related to lesser mandibular musculature, such as the smaller fossa temporalis and the processus paroccipitalis lacking a flange on its anteromedial margin. Similarly, structures associated with the neck musculature differ, such as the relatively smaller mamillar tuberosities and the associated absence of a distinct fossa parabasalis and more distinct intermediary insertions of the neck muscles for m. rectus capitus ventralis. These latter differences are likely to be associated with the smaller size of the head in Ilbandornis and thus are of little phylogenetic significance. The available cranial material of Barawertornis tedfordi does not differ from that of species of Ilbandornis except in size and a few minor features revealing that this older and smaller species belongs to the Ilbandornis lineage. In total, the differences between species in the Ilbandornis/Barawertornis lineage and those of Dromornis are relatively minor and suggest that these lineages are little divergent. There is no informative cranial material known for Genyornis newtoni: the often published figure of a skull of this species (e.g., Murray and Vickers-Rich; 2004), actually shows a pile of fragments carved from the substrate in the shape of an aepyornithid skull. It includes an occipital condyle fragment aligned at 90 to that expected and essentially not one other identifiable osteological structure. The cranial diversity now known for dromornithids encompasses less variation than seen in the single ratite moa genus Pachyornis (Emeidae, Dinornithiformes), which has only three species. In this genus, P. elephantopus Owen, 1856, has a much elongated preorbital area compared with the other species. Relative length and width vary substantially, being broad in P. australis Oliver, 1949, and the relative size of the temporal fossae vary markedly, being small in P. geranoides Owen, 1848 (Worthy, 1989; Worthy and Scofield, 2012). The various genera of moa encompass even greater variability in their bill and cranial morphology (Worthy and Scofield, 2012), thus calling into question the current generic diversity for dromornithids and appearing to reflect geological age rather than morphological differences. The description of D. murrayi, n. sp., increases the known diversity of dromornithids to eight species in four genera. There are four Dromornis species: D. australis of unknown, but likely Pliocene-Pleistocene age, D. stirtoni of late Miocene age (8– 6 Ma; Alcoota and Ongeva LFs), D. planei of middle Miocene age (12 Ma; Bullock Creek LF), and D. murrayi, n. sp., of late Oligocene to early Miocene age (24–17 Ma) (Murray and Vickers-Rich, 2004). The Ilbandornis/Barawertornis lineage enters the known fossil record with B. tedfordi in the late Oligocene to early Miocene (24–17 Ma) and proceeds in the Bullock Creek and Alcoota LFs with two species of Ilbandornis. By the late Pleistocene, just one lineage survived, represented by Genyornis newtoni. The data presented herein reveal that this diversity reflects only two lineages evolving in parallel from the late Oligocene through to the late Miocene and thereafter reduction to just one. Species of the Ilbandornis lineage increased in size from the late Oligocene to the late Miocene, when two ostrich-sized taxa existed, with I. lawsoni much more cursorial than I. woodburnei and the latter representing a slightly heavier bird (Worthy and Yates, 2015). After the Ongeva LF was deposited, the fossil record is almost bereft of dromornithids until the late Pleistocene when Genyornis newtoni is found to be the only exemplar of the family. The exceptions are a few bones of an undescribed form, tentatively assigned to Ilbandornis on the basis of size, from the Pliocene Curramulka LF (Pledge, 1992) and D. australis. Features of the postcranial skeleton of G. newtoni, the cranium being unknown, suggest that this latest surviving species is also from the Ilbandornis lineage, and if so, indicates that there was further increase in size after the late Miocene. However, this hypothesis remains to be tested in a phylogenetic analysis and by recovery of cranial material, which is the subject of ongoing work (Worthy, unpubl. data). The Dromornis taxa increase in size from the older Oligocene species to a maximum in the Alcoota LF, where D. stirtoni became the largest bird known globally at perhaps 350–650 kg (Murray and Vickers-Rich, 2004). The fossil record shows that dromornithids had evolved two lineages and attained their characteristic morphology by the late Oligocene, and changed little over the next 25 million years until the extinction of the group in the late Pleistocene. Specifically, dromornithids of late Oligocene age already had highly reduced pectoral girdle elements similar to those present in the Pleistocene Genyornis newtoni, as described by Stirling and Zietz (1900). There are older, undescribed fragmentary remains known from the Pwerte Marnte Marnte LF of the Northern Territory, also considered of late Oligocene age (Murray and Megirian, 2006), but as yet these reveal little more than that large taxa existed. These observations imply a long ghost lineage extending from presumably volant ancestors for which the only hint of a precursor is the mould of fossil footprints of Eocene age (Vickers-Rich and Molnar, 1996). The lack of terrestrial vertebrate sites sampling the interval between the early Eocene and late Oligocene (Black et al., 2012) makes the problem of this early period of evolution intractable at present. The diversity of dromornithids, with a maximum of three contemporary species, compares markedly to the dinornithiform (moa) ratite radiation in New Zealand, where nine species were contemporary, with up to four species coexisting in habitats and Downloaded by [Flinders University of South Australia], [Dr TH Worthy] at 17:21 18 February 2016 Worthy et al.—Oligo-Miocene dromornithids (e1031345-20) seven species found on South Island (Worthy and Holdaway, 2002; Worthy and Scofield, 2012). As for the dromornithids, the ratite fauna in Australia was also of limited diversity, with one species of an ancestral emu (Emuarius) known at any one time from the late Oligocene through to the late Miocene and just one fossil cassowary Casuarius (Worthy et al., 2014). Just the one species each of Dromaius and Casuarius exist in the extant mainland fauna (Christidis and Boles, 2008). In Australia, the lower diversity of the giant browsing birds, both ratites and dromornithids, probably relates to the highly diverse co-occurring browsing mammalian fauna (Black et al., 2012), which is hypothesized to have similarly formed diversity constraints for ratites on other Gondwanan landmasses (Mitchell et al., 2014). A parallel is seen in the Madagascan fauna, where the extinct elephant birds, which coexisted with a suite of browsing mammals, probably had a real diversity of just three species, two in Aepyornis and one in Mullerornis (Worthy and Holdaway, 2002). ACKNOWLEDGMENTS This research is part of Australian Research Council DECRA project DE130101133, ‘Evolution, breeding biology, and extinction of giant fowl in Australia and the southwest Pacific’ (to T. H. Worthy). Riversleigh specimens have been collected and processed with the support of Australian Research Council grants LP100200486, DP1094569, DP130100197, and DE130100467 (to M. Archer, S. J. Hand, and K. H. Black). For access to specimens, we thank A. Yates, Museum of Central Australia, Alice Springs, Northern Territory; W. Boles, Australian Museum, Sydney, New South Wales; J. R. Laurie, Geoscience Australia, Canberra; A. Rozefelds and K. Spring, Queensland Museum, Brisbane, Queensland; C. Reid, Queen Victoria Museum and Art Gallery, Launceston, Tasmania; K. Hughes and John Scanlon for preparation, Outback-at-Isa, Mt. Isa, Queensland; A. K. Gillespie, T. Myers, and K. H. Black, School of Biological Earth and Environmental Science, University of New South Wales, Sydney, New South Wales; and M. Binnie, South Australian Museum, Adelaide, South Australia. G. Gully (Flinders University) helped with photography, and we thank V. De Pietri for comments on a draft. LITERATURE CITED Agnolın, F. L. 2007. Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno medio de Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales 9:15–25. Andors, A. V. 1992. 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The extinct flightless mihirungs (Aves, Dromornithidae): Cranial anatomy, a new species, and assessment of Oligo-Miocene lineage diversity

The extinct flightless mihirungs (Aves, Dromornithidae): Cranial anatomy, a new species, and assessment of Oligo-Miocene lineage diversity

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