SAURISCHIA SEELEY, 1887 SENSU GAUTHIER, 1986

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 : 13-15

SAURISCHIA SEELEY, 1887 SENSU GAUTHIER, 1986 (=EUSAU- RISCHIA PADIAN ET AL., 1999)

FIG. 6I–T

Referred specimens and localities — PEFO 21660/ UCMP 126751 ( Fig. 6I, J), distal end of right femur, PFV 071: Flattops W, UCMP V 82259, PFM; PEFO 33956 ( Fig. 6K–L), distal end of right femur, PFV 231: The Giving Site, PFM; PEFO 44469 ( Fig. 6M, N), distal end of right femur, PFV 451: Black Knoll E, PFM; PEFO 34562 ( Fig. 6O, P), distal end of left femur, PFV 184: Clambake Amphitheater, PFM; PEFO 44474 ( Fig. 6Q, R), distal end of left femur, PFV 492: Dead Wash NW2, PFM; PEFO 42987/ UWBM 117640 ( Fig. 6S, T), distal end of left femur, PFV 410: Kaye Quarry, UWBM C2226, Jim Camp Wash beds, SM.

Description and rationale for assignment —These distal ends of femora are all broken distal to the fourth trochanter, but they all preserve the distal medial and lateral condyles and crista tibiofibularis, except PEFO 33956 ( Fig. 6K), which is lacking most of the crista tibiofibularis. In all of the specimens, a groove divides the lateral condyle and crista tibiofibularis in distal view (Nesbitt 2011:322-1) ( Fig. 6I), which is a synapomor- phy of Saurischia , e.g., Herrerasaurus ischigualastensis (PVSJ 373, Novas 1993: fig. 7f), Saturnalia tupiniquim (MCP PV 3844, Langer 2003: fig. 4d), and ‘ Syntarsus ’ kayentakatae (MNA V2623). Furthermore, this groove opens posterolaterally in an obtuse angle in distal view in all these specimens. Shuvosaurid pseudosuchians have a similar morphology in the distal end of the femur but can be differentiated as their groove opens at a 90° angle (Parker and Irmis 2005). A similar groove is also

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present convergently in lagerpetids (Garcia et al. 2019: fig. 7a–h), but in that group the crista tibiofibularis is greatly enlarged and is larger than the medial condyle in distal view (Nesbitt 2011:326-1), e.g., Dromomeron romeri (GR 218, Nesbitt et al. 2009b: fig. 1d).

In distal view, the posterior margin of the medial condyle is rounded in PEFO 21660/UCMP 126751 ( Fig. 6I), PEFO 44469 ( Fig. 6M), and PEFO 44474 ( Fig. 6Q), and pointed in PEFO 33956 ( Fig. 6K), PEFO 34562 ( Fig. 6O), and PEFO 42987/UWBM 117640 ( Fig. 6S). A round medial condyle is present in most early dinosaur groups, including ornithischians, e.g., Eocursor parvus (SAM-PK-K8025, Butler 2009: fig. 15f), and Scutellosaurus lawleri (MNA V175), early sauropodomorphs, e.g., Buriolestes schultzi (ULBRA-PVT280, Cabriera et al. 2016: fig. s2e), and Sa. tupiniquim (MCP PV 3844, Langer 2003: fig. 4d), early theropods, e.g., Tawa hallae (GR 244, Nesbitt 2011: fig. 39b), and H. ischigualastensis (PVSJ 373, Novas 1993: fig. 7f), and stem-averostrans, e.g., Dilophosaurus wetherilli (UCMP 37302, Marsh and Rowe 2020: fig. 20.6), and Cryolophosaurus ellioti Hammer and Hickerson (1994, FMNH PR 4923). A pointed medial condyle is present in the large-bodied coelophysid specimens from PEFO (PEFO 21373/UCMP 129618 and PEFO 33981). In distal view, the crista tibiofibularis and lateral condyle are not well separated from one another in PEFO 44474 ( Fig. 6Q), much like the condition found in Chindesaurus bryansmalli (PEFO 10395, Marsh et al. 2019a: fig. 7f) and T. hallae (GR 244, Nesbit 2011: fig. 39b). In the other specimens ( Fig. 6O), the crista tibiofibularis and lateral condyle are distinctly separate structures and resemble the distal outline of theropods such as coelophysids and stem-averostran (Ezcurra 2017: figs. 4.1, 4.3, 4.4, 4.6, 4.7). We assign these distal femora to Saurischia owing to the presence of a groove between the lateral condyle and crista tibiofibularis that opens at an obtuse angle in distal view.