COELOPHYSIDAE NOPSCA, 1923 SENSU TYKOSKI, 2005

Marsh, Adam D. & Parker, William G., 2020, New dinosauromorph specimens from Petrified Forest National Park and a global biostratigraphic review of Triassic dinosauromorph body fossils, PaleoBios 37, pp. 1-56 : 23-27

COELOPHYSIDAE NOPSCA, 1923 SENSU TYKOSKI, 2005

FIGS. 13A–N, 14A–L, 15A–I

Referred specimens and localities — PEFO 21373/ UCMP 129618 ( Fig. 13), partial skeleton including a right ilium ( Fig. 13A), right astragalocalcaneum ( Fig. 13J–K),

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left femur ( Fig. 13B–F), left tibia and fibula ( Fig. 13G–I), and partial right pes ( Fig. 13L–N), PFV 040: Dinosaur Hill, UCMP V 82250, PFM; PEFO 33981 ( Fig. 14), partial skeleton including left ( Fig. 14A–C) and right femora ( Fig. 14D–E), right ( Fig. 14F–J) tibia, and left astragalocalcaneum ( Fig. 14K–L), PFV 231: The Giving Site, PFM; PEFO 33983 ( Fig. 15), partial skeleton including proximal end of right femur ( Fig. 15A–B), right tibia ( Fig. 15C–G), right astragalocalcaneum ( Fig. 15I), and distal tarsal 4 ( Fig. 15H), PFV 231; The Giving Site, PFM).

Description and rationale for assignment— The three partial skeletons have preserved elements in common that aid in identifying the specimens, namely the proximal ends of femora, distal ends of femora (except for PEFO 33983), proximal and distal ends of tibiae, astragalocalcanea, and distal tarsal 4 (except for PEFO 33981). Three additional apomorphies of Neotheropoda are present on the distal end of the tibiae of these specimens: a subrectangular distal outline (Rauhut 2003:208-1) ( Fig. 15E) that has a concave posterolateral margin (Nesbitt 2011:335-1) and a proximodistal ridge on the posteromedial surface (Langer and Benton 2006; Nesbitt 2011:336-1). A concave posterolateral margin of the tibia in distal view is also present in some early sauropodomorphs, e.g., Saturnalia tupiniquim (MCP PV 3844, Langer 2003: fig. 5h), and the posteromedial ridge is variably present in other early dinosaurs such as Lesothosaurus diagnosticus (NHMUK PV RU B17, Baron et al. 2017a: fig. 15c), Eodromaeus murphii (PSVJ 562, Ezcurra 2017), and Sarahsaurus aurifontanalis Rowe et al., 2010 (TMM 43646-2.173, Marsh and Rowe, 2018: fig. 37b). Distal tarsal 4 is preserved in PEFO 21373/UCMP 129618 and PEFO 33983; the medial process found in saurischian dinosaurs, e.g., Sa. tupiniquim , (MCN PV 3844, Nesbitt 2011: fig. 42g) is present but rounded (Nesbitt 2011:235-1) ( Fig. 13L), and like the fourth distal tarsal of other neotheropods, e.g., Dilophosaurus wetherilli (UCMP 37302, Marsh and Rowe, 2020: fig. 24.48), the posterior process is has a straight posterior margin (Nesbitt 2011:350-0, reversal).

These specimens also preserve apomorphies of the Coelophysidae . The partial skeleton PEFO 21373/UCMP 129618 (Padian 1986) includes a nearly complete right ilium with a prominent supraacetabular crest that projects ventrally (Gauthier 1986, Nesbitt 2011:264-1) ( Fig. 13A). This condition is best seen in the coelophysids Coelophysis bauri (MNA V3318) and Megapnosaurus rhodesiensis (BP/1/5246, Munyikwa and Raath 1999: fig. 2b), as well as the stem-averostran Di. wetherilli (TMM 43646-1.60, Marsh and Rowe 2020: fig. 49.1) and some poposauroid pseudosuchians such as Poposaurus gracilis (YPM 57100, Schachner et al. 2019: fig. 26e) and Effigia okeeffeae (AMNH FR 30588, Nesbitt 2007: fig. 32). Additionally, PEFO 21373/UCMP 129618 ( Fig. 13F) and PEFO 33981 ( Fig. 14E) preserve the infrapopliteal ridge on the femur that connects the crista tibiofibularis and medial condyle posteriorly (Tykoski 2005, Marsh and Rowe 2020:240-1), which is best exemplified in ‘ Syntarsus ’ kayentakatae (MNA V2623, Rowe 1989: fig. 4f) and C. bauri (TMM 45559-12), but is also convergently present in ceratosaurs such as Ceratosaurus nasicornis Marsh (1884) (UMNH VP 5278, Madsen and Welles 2000: pl. 21c) and Carnotaurus sastrei Bonaparte (1985) (MACN- CH 894, Bonaparte1990: fig. 32c).

As in other neotheropods, e.g., C. bauri (AMNH FR 30576, Nesbitt 2011: fig. 46e, and Di. wetherilli (UCMP 37302, Marsh and Rowe 2020: fig. 23.3), the astragalus lacks the basin posterior to the ascending process found in most early saurischians (Nesbitt 2011:359-0) ( Fig. 15I). Unlike non-dinosaur avemetatarsalians and early dinosaurs, e.g., Teleocrater rhadinus (NMT RB490, Nesbitt et al. 2017: fig. 2n), Asilisaurus kongwe (NMT RB159, Nesbitt et al. 2019: fig. 50), Eoraptor lunensis (PVSJ 559, Sereno et al. 2012: fig. 88g), and Scutellosaurus lawleri (MNA V175, Colbert 1981: fig. 30c), the proximal tarsals of these three PEFO specimens ( Fig. 13J, 14K, 15I) are co-ossified to form an astragalocalcaneum (Tykoski 2005:149, Nesbitt 2011:370-1). Coossified proximal tarsals are apomorphic for pterosaurs, e.g., Dimorphodon macronyx Buckland (1829) (YPM 9182, Padian 1983: fig. 18c), lagerpetids, e.g., Dromomeron romeri (GR 223, Nesbitt et al. 2009b: fig. 7a), Heterodontosaurus tucki (SAM-PK-K1332, Santa Luca 1980: fig. 19), coelophysids, e.g., C. bauri (AMNH FR 30576, Nesbitt 2011: fig. 46e) and ‘ S.’ kayentakatae (MNA V2623, Rowe 1989: fig. 6a), and ceratosaurs, e.g, Ce. nasicornis (UMNH VP 5278, Madsen and Welles 2000: pl. 22a), and Majungasaurus crenatissimus Depéret (1896) (FMNH FR 2278, Carrano 2007: fig. 9d). In some of these taxa, e.g., pterosaurs, Heterodontosaurus tucki , and ‘ S.’ kayentakatae, the distal tarsals are also co-ossified to the distal ends of the tibia and fibula to form a tibiotarsus; at least in coelophysids the degree of coossification between the astragalocalcaneum, tibia, and fibula is ontogenetically variable (Tykoski 2005, Griffin 2018). We assign these three partial skeletons to the Coelophysidae owing to the presence of the infrapopliteal ridge on the distal end of the femur and the coossifed proximal tarsals.