Ornithopod diversity in the Griman Creek Formation (Cenomanian), New South Wales, Australia

Abstract

During the Early Cretaceous, dinosaur communities of the Australian-Antarctic rift system (Eumeralla and Wonthaggi formations) cropping out in Victoria were apparently dominated by a diverse small-bodied ‘basal ornithopod’ fauna. Further north, in Queensland (Winton and Mackunda formations), poorly-represented small-bodied ornithopods coexisted with large-bodied iguanodontians. Our understanding of the ornithopod diversity from the region between the Australian-Antarctic rift and Queensland, represented by Lightning Ridge in central-northern New South Wales (Griman Creek Formation), has been superficial. Here, we re-investigate the ornithopod diversity at Lightning Ridge based on new craniodental remains. Our findings indicate a diverse ornithopod fauna consisting of two-to-three small-bodied non-iguanodontian ornithopods (including Weewarrasaurus pobeni gen. et sp. nov.), at least one indeterminate iguanodontian, and a possible ankylopollexian. These results support those of previous studies that favour a general abundance of small-bodied basal ornithopods in Early to mid-Cretaceous high-latitude localities of southeastern Australia. Although these localities are not necessarily time-equivalent, increasing evidence indicates that Lightning Ridge formed a ‘meeting point’ between the basal ornithopod-dominated localities in Victoria and the sauropod-iguanodontian faunas in Queensland to the north.

High-latitude neonate and perinate ornithopods from the mid-Cretaceous of southeastern Australia

“…Nevertheless, four taxa have been named from these deposits: Leaellynasaura amicagraphica, Qantassaurus intrepidus, Atlascopcosaurus loadsi , and Diluvicursor pickeringi 23,24,37 . Molnar and Galton 56 identified two femoral morphotypes from the Griman Creek Formation and craniodental remains suggest that up to three small-bodied non-iguanodontian ornithopods were present 22 . Larger-bodied iguanodontians were also present in the Griman Creek Formation but are absent from the Eumeralla and Wonthaggi formations 9,22,57 .…”

“…The high-paleolatitude (~60–70°S) mid-Cretaceous Australian dinosaur faunas of the Griman Creek, Eumeralla, and Wonthaggi formations preserve a particularly diverse array of small-bodied, bipedal non-iguanodontian ornithopods 9,12,22–24 . The diversity of these animals suggests that they were well suited to the high-latitude conditions 23,24 , although their breeding habits remain unknown, due to the absence of appropriate material.…”

“…Here, we describe two miniscule and partial ornithopod femora from the Griman Creek Formation (GCF; Cenomanian 9 ) in central-northern New South Wales, Australia, and build upon previous descriptions of femora from the Eumeralla and Wonthaggi formations. Although histological analysis is obviated by the pseudomorphic opalization of some fossils from the Griman Creek Formation (opalised fossils typically do not preserve bone microstructure) 22 , gross anatomical comparisons with the histologically sampled specimens from the Eumeralla and Wonthaggi formations 25,26 indicate that the GCF specimens represent perinate (around the point of hatching) individuals. Together, these specimens constitute the first evidence of perinatal dinosaurs from Australia and, more broadly, the first insights into the high-latitude breeding preferences of non-iguanodontian ornithopods in Gondwana.…”

Isisfordia molnarisp. nov., a new basal eusuchian from the mid-Cretaceous of Lightning Ridge, Australia

“…The Griman Creek Formation at Lightning Ridge was previously considered Albian in age (e.g., Dettman et al, 1992; Smith, 1999; Smith & Kear, 2013), but recent radiometric dating indicates a Cenomanian (96.6–100.2 Ma; Bell et al, 2019) age, slightly younger than the lower Winton Formation at Isisford (see Tucker et al, 2013). The Griman Creek Formation has produced a diverse assemblage of vertebrate fossils (see Bell et al, 2019 for a comprehensive overview) apart from crocodyliforms, including aspidorhynchids (Bell et al, 2019), lamniforms (Bell et al, 2019), dipnoans (Kemp, 1997a; Kemp, 1997b), meiolaniform and chelid testudines (Smith, 2009; Smith, 2010; Smith & Kear, 2013), leptocleidid plesiosaurs (Kear, 2006), anhanguerian pterosaurs (Brougham, Smith & Bell, 2017), ankylosaurians (Bell, Burns & Smith, 2017), small and large bodied ornithopods (Molnar & Galton, 1986; Molnar, 1996; Bell et al, 2018), titanosauriform sauropods (Molnar & Salisbury, 2005), megaraptorid theropods (Bell et al, 2015; Brougham, Smith & Bell, 2019), enantiornithes (Bell et al, 2019) and australosphenid mammals (Archer et al, 1985; Flannery et al, 1995; Clemens, Wilson & Molnar, 2003; Pian et al, 2016; T. Rich in Poropat et al, 2018).…”

New theropod (Tetanurae: Avetheropoda) material from the ‘mid’-Cretaceous Griman Greek Formation at Lightning Ridge, New South Wales, Australia

“…The Griman Creek Formation at Lightning Ridge preserves a rich array of vertebrate and invertebrate fauna, including crocodylomorphs [23,28,29], australosphenidian mammals [30–32], ornithischian dinosaurs [33–35], titanosauriform sauropods [36], megaraptoran theropods [18,37], enantiornithine birds [38], pterosaurs [39], plesiosaurs [40], turtles [41,42], dipnoan lungfish [43–45], a possible synapsid [24] and numerous species of non-marine macro-invertebrates [22,46–48]. For a review of the vertebrate fauna of the Griman Creek Formation, see Bell et al .…”