ARCHOSAURIA COPE, 1869 SENSU NESBITT, 2011 AVEMETATARSALIA BENTON, 1999 SENSU NESBITT ET AL.

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 : 9

ARCHOSAURIA COPE, 1869 SENSU NESBITT, 2011 AVEMETATARSALIA BENTON, 1999 SENSU NESBITT ET AL.,

2017 ORNITHODIRA GAUTHIER, 1986 SENSU NESBITT ET AL., 2017

FIG. 4A–J

Referred specimens and localities — PEFO 36741 ( Fig. 4A–E), left metatarsal I, PFV 215: Zuni Well Mound, PFM; PEFO 44217 ( Fig. 4F–J), right metatarsal I, PFV 217: Dinosaur Wash, BMM.

Description and rationale for assignment —Metatarsals I of PEFO 36741 and PEFO 44217 are proportionally long and slender metapodials and, as observed by the crushing of PEFO 34741, hollow. The proximal end of PEFO 34371 is twisted with respect to the distal end. In proximal view, the medial surface is nearly straight where it would articulate with metatarsal II, and the lateral edge is rounded, making a subtriangular proximal outline ( Fig. 4D, I). The proximal outline is mediolaterally narrow, which indicates that the metatarsus was compact, not splayed (Ezcurra 2016:565-1). A compact metatarsus is present in ornithodirans and some early crocodylomorphs (Nesbitt 2011, Ezcurra 2016). The proximal surface of PEFO 36741 and PEFO 44217 is flat, would articulate with the distal tarsals, and would reach the proximal extent of metatarsal II, unlike in neotheropods where metatarsal I is more distally placed along the back of the metatarsus (Rauhut 2003, Nesbitt 2011:385-1). The distal end is asymmetrical, such that the medial condyle is more prominent than the lateral ( Fig. 4E, J). Both distal condyles have a collateral ligament fossa. In dorsal view, the medial condyle projects distally further than the lateral. The distal condyles of metatarsal I in the crocodylomorphs Protosuchus richardsoni Brown (1933) (AMNH FR 3024), Colbert and Mook 1951: fig. 20b) and Terrestrisuchus gracilis Crush (1984) are not asymmetrical (Crush 1984: fig. 10e). Asymmetrical distal condyles of metatarsal I are found in Heterodontosaurus tucki Crompton and Charig (1962, SAM-PK-K1332) (Santa Lucas 1980: fig. 20b), Eoraptor lunensis Sereno et al. (1993, PVSJ 512) (Sereno et al. 2012: fig. 91b), Saturnalia tupiniquim Langer et al. (1999, MCP PV 3844) (Langer 2003: fig. 7e), Herrerasaurus ischigualastensis Reig (1963, PVSJ 373) (Novas 1993: fig. 9j) and Coelophysis bauri (MNA V3320, Nesbitt 2011: fig. 48f), but not in the non-dinosaur dinosauriform Asilisaurus kongwe Nesbitt et al. (2010, NMT RB159) (Nesbitt et al. 2019: fig. 53e). The PEFO specimens are identical to metatarsal I of GR 1033 (Nesbitt et al. 2009a: fig. 2j), a partial skeleton of Tawa hallae Nesbitt et al. (2009a) . We assign PEFO 36741 and PEFO 44217 to non-neotheropod Ornithodira owing to the presence of a compact metatarsal I that is not distally positioned down the metatarsus.