Monday, March 11, 2019

[Paleontology • 2019] Galleonosaurus dorisae • New Small-bodied Ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic Rift System, with Revision of Qantassaurus intrepidus


Galleonosaurus dorisae 
Herne, Nair, Evans & Tait, 2019


Abstract
The Flat Rocks locality in the Wonthaggi Formation (Strzelecki Group) of the Gippsland Basin, southeastern Australia, hosts fossils of a late Barremian vertebrate fauna that inhabited the ancient rift between Australia and Antarctica. Known from its dentary, Qantassaurus intrepidus Rich and Vickers-Rich, 1999 has been the only dinosaur named from this locality. However, the plethora of vertebrate fossils collected from Flat Rocks suggests that further dinosaurs await discovery. From this locality, we name a new small-bodied ornithopod, Galleonosaurus dorisae n. gen. n. sp. from craniodental remains. Five ornithopodan genera are now named from Victoria. Galleonosaurus dorisae n. gen. n. sp. is known from five maxillae, from which the first description of jaw growth in an Australian dinosaur is provided. The holotype of Galleonosaurus dorisae n. gen. n. sp. is the most complete dinosaur maxilla known from Victoria. Micro-CT imagery of the holotype reveals the complex internal anatomy of the neurovascular tract and antorbital fossa. We confirm that Q. intrepidus is uniquely characterized by a deep foreshortened dentary. Two dentaries originally referred to Q. intrepidus are reassigned to Q. ?intrepidus and a further maxilla is referred to cf. Atlascopcosaurus loadsi Rich and Rich, 1989. A further ornithopod dentary morphotype is identified, more elongate than those of Q. intrepidus and Q. ?intrepidus and with three more tooth positions. This dentary might pertain to Galleonosaurus dorisae n. gen. n. sp. Phylogenetic analysis recovered Cretaceous Victorian and Argentinian nonstyracosternan ornithopods within the exclusively Gondwanan clade Elasmaria. However, the large-bodied taxon Muttaburrasaurus langdoni Bartholomai and Molnar, 1981 is hypothesised as a basal iguanodontian with closer affinities to dryomorphans than to rhabdodontids.



Figure 4. Specimens of Galleonosaurus dorisae n. gen. n. sp. from the Flat Rocks Sandstone in the upper Barremian, Wonthaggi Formation, Gippsland Basin, southeastern Australia:
(1–2) holotype (NMV P229196), left maxilla in lateral (1) and medial (2) views; (3) NMV P208178, left maxilla in lateral view; (4) NMV P212845, left maxilla in lateral view; (5) NMV P209977, left maxilla in lateral view; (6) NMV P186440, left maxilla in lateral view; (7) NMV 208113, right maxillary tooth in labial view.

Scale bars = 10 mm (1–6); 1 mm (7).

Systematic paleontology

Dinosauria Owen, 1842
Ornithischia Seeley, 1888
Neornithischia Cooper, 1985
Cerapoda Sereno, 1986
Ornithopoda Marsh, 1881

Genus Galleonosaurus new genus

Type species: Galleonosaurus dorisae n. gen. n. sp., by monotypy.


Etymology: From galleon (Latinization of the English for a type of large sailing ship) + saurus (New Latin from the Greek sauros for lizard), in reference to the appearance of the maxilla to the upturned hull of a galleon.

Occurrence: Flat Rocks locality in the Inverloch region of Victoria, southeastern Australia (Fig. 1); Flat Rocks Sandstone and The Caves Sandstone, upper Barremian of the Wonthaggi Formation in the Gippsland Basin.

Remarks: Prior to the recognition of Galleonosaurus n. gen., Atlascopcosaurus loadsi and Leaellynasaura amicagraphica were the only Victorian ornithopods identified from maxillary remains (Rich and Rich, 1989). The maxillae of Atlascopcosaurus loadsi are highly incomplete and the only known maxilla of L. amicagraphica (that of the holotype, NMV P185991) is damaged, and due to its diminutive size, difficult to study. The maxillae of Galleonosaurus n. gen., as well as the complete palatine and fragment of the lacrimal, now provide new information from which the anatomy of the other Victorian ornithopods can be better understood. The holotype of Galleonosaurus dorisae n. gen. n. sp. (NMV P229196) represents the most complete maxilla of a dinosaur currently known from Victoria.

Diagnosis: Small-bodied, noniguanodontian ornithopod characterized by five potential autapomorphies: (1) ascending ramus of maxilla has two slot-like foramina on the anterior margin that communicate with the neurovascular tract; (2) neurovascular tract bifurcates internally to exit at two anteroventral maxillary foramina; (3) lingual margin of maxillary tooth roots in midregion of tooth row form an S-bend at their bases; (4) posterior third of maxilla on some, but not all, specimens deflects posterolaterally at an abrupt kink; and (5) lateral end of palatine lateral ramus forms a hatchet-shaped flange.

Occurrence: Flat Rocks locality in the Inverloch region of Victoria, southeastern Australia (Fig. 1); Flat Rocks Sandstone and The Caves Sandstone, upper Barremian of the Wonthaggi Formation in the Gippsland Basin.

Etymology: dorisae, in recognition of Doris Seegets-Villiers for her geological, palynological, and taphonomic work on the Flat Rocks fossil vertebrate locality.



Figure 1. Maps of Australia, southern Victoria and Gondwana: (1) present-day eastern Australia indicating region of interest; (2) inset from (1) showing upper Barremian–lower Albian ornithopod localities and associated geology; (3) reconstruction of Gondwana during the late Barremian (~ 125 Ma) using GPlates (www.gplates.org). Dashed lines in (2) indicate basin boundaries. Geological information in (2) based on Bryan et al. (1997, 2000). V-shaped symbols in (3) indicate direction and position of plate subduction, based on Wandres and Bradshaw (2005). Australian paleoshoreline in (3) based on Heine et al. (2015). Dashed arrows in (2–3) indicate paleoflow direction. AAR = Australian-Antarctic rift; AF = Africa; AN = Antarctica; AU = Australia; I = India; EF = Eumeralla Formation; ES = epeiric Eromanga Sea (in region of Eromanga Basin); ETRW = Eric the Red West; M = Madagascar; NC = New Caledonia; NZ = New Zealand; SA = South America; VHFT2 = Victorian Hypsilophodontid Femur Type 2; VOPC1 = Victorian ornithopod postcranium 1 (NMV P185992/P185993); VOPC2 = Victorian ornithopod postcranium 2 (NMV P186047); W = Whitsunday Large Siliceous Igneous Province (Bryan et al., 1997); WF = Wonthaggi Formation.

Figure 27. Australian ornithopod occurrences: ETRW = Eric the Red West; VHFT2 = Victorian Hypsilophodontid Femur Type 2; VOD2 = Victorian ornithopod dentary morphotype 2; VOD3 = Victorian ornithopod dentary morphotype 3; VOM4 = Victorian ornithopod maxilla morphotype 4; VOPC1 = Victorian ornithopod postcranium 1 (NMV P185992/P185993); VOPC2 = Victorian ornithopod postcranium 2 (NMV P186047). See Table 5 for associated information on ornithopod occurrences.

Figure 28. Time-calibrated phylogeny of the ornithopods from the IW strict consensus cladogram (Fig. 25.2). Dashed lines indicate unknown times of Pangaean branch/lineage divergences prior to the middle Callovian. Time scale based on Cohen et al. (2013). Thick lines indicate taxon (graduated shaded lines) and clade (solid lines) durations (for sources, see Text S1). Aal = Aalenian; AF = Africa; Alb = Albian; AN = Antarctica; Apt = Aptian; AU = Australia; Baj = Bajocian; Bar = Barremian; Bat = Bathonian; Ber = Berriasian; Cal = Callovian; Cam = Campanian; Cen = Cenomanian; Con = Coniacian; Hau = Hauterivian; Kim = Kimmeridgian; LA = Laurasia; Maa = Maastrichtian; NZ = New Zealand; Oxf = Oxfordian; SA = South America; San = Santonian; Tit = Tithonian; Tur = Turonian; Val = Valanginian.


Conclusions: 
The identification of the new ornithopod, Galleonosaurus dorisae n. gen. n. sp., and three further jaw morphotypes (VOM4, VOD2, and VOD3) from the Flat Rocks locality in the upper Barremian Wonthaggi Formation complements the four previously named ornithopods from Victoria—Atlascopcosaurus loadsi, Diluvicursor pickeringi, Leaellynasaura amicagraphica, and Qantassaurus intrepidus. Although synonymy between some of these taxa is possible, Galleonosaurus dorisae n. gen. n. sp. and the newly identified craniodental morphotypes confirm that a highly diverse small-bodied ornithopod fauna flourished in the periodically disturbed, high-latitude, riverine floodplain environment of the Australian-Antarctic rift valley (see also Rich and Rich, 1989; Rich and Vickers-Rich, 1999, 2000; Rich et al., 2002; Herne et al., 2016, 2018).

The new dentary morphotype from the Flat Rocks Sandstone (VOD3) confirms the presence of an ornithopod with a more elongate dentary than that of Qantassaurus intrepidus, from the same locality, and with more alveoli in specimens of similar size (15 alveoli compared to 10). We speculate that VOD3 is a more likely candidate for the presently unknown dentary of Galleonosaurus dorisae n. gen. n. sp. than the dentary of Q. intrepidus, although this suggestion cannot be presently confirmed. The similarity between the dentary teeth of VOD3 and an isolated dentary tooth (QM F52774) discovered in the Winton Formation, central-western Queensland (Hocknull and Cook, 2008) suggests that the spatiotemporal range of potentially closely related ornithopods in eastern Australia extended from at least the upper Barremian of the Australian-Antarctic rift system to the lower Turonian of the Eromanga Basin (Figs. 1.3, 27).

The phylogenetic analysis (Figs. 25.2, 26) recovered the Victorian ornithopods Diluvicursor pickeringi, Leaellynasaura amicagraphica, and Galleonosaurus dorisae n. gen. n. sp. within Elasmaria (Calvo et al., 2007). In addition to the Victorian taxa, Elasmaria also comprises the Argentinian taxa Anabisetia saldiviaiGasparinisaura cincosaltensisMacrogryphosaurus gondwanicus, and Talenkauen santacrucensis. Increased anatomical understanding of the ornithopods recovered within Elasmaria, and particularly the Victorian ornithopods, will undoubtedly impel renewed phylogenetic assessment. The large-bodied Australian genus Muttaburrasaurus, however, is a nonelasmarian and was recovered within Iguanodontia. The time-calibrated phylogeny derived from the IW strict consensus tree (Fig. 28) suggests that Elasmaria and the stem of Muttaburrasaurus langdoni had their origins in Pangaea prior to the opening of seaways between Gondwana and Laurasia in the middle Callovian.


Matthew C. Herne, Jay P. Nair, Alistair R. Evans and Alan M. Tait. 2019. New Small-bodied Ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic Rift System, with Revision of Qantassaurus intrepidus Rich and Vickers-Rich, 1999Journal of Paleontology. First View. DOI: 10.1017/jpa.2018.95

New wallaby-sized dinosaur from the ancient Australian-Antarctic rift valley https://phys.org/news/2019-03-wallaby-sized-dinosaur-ancient-australian-antarctic-rift.html via @physorg_com

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