Vancleavea campi, Long and Murry, 1995

Lessner, Emily J., Parker, William G., Marsh, Adam D., Nesbitt, Sterling J., Irmis, Randall B. & Mueller, Bill D., 2018, New insights into Late Triassic dinosauromorph-bearing assemblages from Texas using apomorphy-based identifications, PaleoBios 35, pp. 1-41 : 20-29

VANCLEAVEA CAMPI Long and Murry, 1995 + LITOROSUCHUS SOMNII Li et al., 2016

Referred Specimens— Humeri: TTU-P 11382, complete right humerus ( Fig. 6G–I) TTU-P 11385, complete left humerus ( Fig. 6J).

Localities— MOTT 3628 (Kirkpatrick Quarry); MOTT 3624 (Post Quarry).

Description and Rationale for Assignment— TTU- P11382 and TTU-P 11385 are nearly identical, complete humeri and are therefore described together with differences noted ( Fig. 6G–J). The proximal end of the humerus is thickened dorsoventrally ( Fig. 6G). The deltopectoral crest is located high on the lateroventral margin proximal to the midshaft ( Fig. 6H, J). In TTU-P 11385 the midshaft is nearly circular and thick in cross-section. The two condyles on the distal end of the humerus expand equally anteriorly and posteriorly ( Fig. 6I). The ulnar condyle is larger than the radial condyle, and the condyles are separated on the lateral surface side by a small fossa that does not extend dorsally onto the shaft. The medial surface of the distal end of the humerus is flat. The absence of the ectepicondylar flange is a synapomorphy for archosau- riforms, and the specimen, the humerus of Vancleavea campi , and the humerus of Litorosuchus somnii lack an ectepicondylar flange (Li et al. 2016; 234:1). TTU-P 11382 is approximately 49.5 mm in length and the proximal and distal ends form an angle of approximately 45°. TTU- P11385 has been deformed during preservation, so we are unable to acquire these measurements though there is obvious torsion between the proximal and distal ends ( Fig. 6G, I). A high angle of torsion between the proximal and distal ends of the humerus is present in the nonarchosauromorph diapsids Petrolacosaurus kansensis , Youngina capensis Broom, 1914 , Planocephalosaurus robinsonae Fraser, 1982 , Gephyrosaurus bridensis Evans, 1980 , and Simoedosaurus lemoinei Gervais, 1877 and the archosauromorphs Prolacerta broomi , Boreopricea funereal Tatarinov, 1978 , “ Chasmatosaurus ” yuani Young, 1936 , and Vancleavea campi ( Ezcurra 2016; 415:0). Litorosuchus has not been scored for a high angle of torsion between the proximal and distal ends of the humerus, but the proximal head is oriented posteromedially with respect to the humeral shaft (Li et al. 2016). On the basis of this character state, the absence of an ectepicondylar flange, and the absence of synapomorphies specific to Litorosuchus or Vancleavea , we assign TTU-P 11382 and TTU-P 11385 to the clade that includes these two taxa.

ARCHOSAURIA Cope, 1869 sensu Gauthier & Padian, 1985

Referred Specimen— TTU-P 11399, distal end of left pubis ( Fig. 7A–C).

Locality— MOTT 3898 (Headquarters South).

Description and Rationale for Assignment — TTU -P11399 preserves the posteriorly expanded distal end of the left pubis as well as a portion of the pubic shaft ( Fig. 7A–C). A posteriorly expanded distal end of the pubis is present among paracrocodylomorphs and saurischians

(Nesbitt 2011; 283:1). The pubic shaft is crescentic in cross-section, narrows more medially than laterally, and is convex anterolaterally and concave posteromedially ( Fig. 7B). The medially-narrowing portion (=midline contact) of the pubic shaft extends distally, forming the anteromedial border of the distal end of the pubis. The area of midline contact does not extend to the distal most end of the pubis and the distal expansions of the pubes would likely not contact when articulated. The specimen is rectangular in anterior view. In lateral view, the pubic shaft widens anteroposteriorly towards the convex, rugose distal end of the pubis. The anterior corner of the distal expansion is just wider than 90° in lateral view, and the posterior border of the distal expansion narrows to a posterodorsally-hooking point ( Fig. 7B). In distal view, TTU-P 11399 is wide anteriorly, tapers posteriorly, and is slightly concave laterally and convex medially ( Fig. 7C). TTU-P 11399 most closely resembles the pubis of Coelophysis bauri (Padian 1986: fig. 5.3), in that there is little dorsal inflection of the posterior tip of the distal end of the pubis, whereas the paracrocodylomorphs such as Poposaurus and Postosuchus have large, sharp dorsal inflections of the posterior tip (Schachner et al. 2011, Parker and Nesbitt 2013, Weinbaum 2013). However, in the absence of any apomorphies specific to Paracrocodylomorpha or Saurischia, we assign TTU- P11399 to Archosauria on the basis of the posteriorly expanded distal end.

PSEUDOSUCHIA Zittel, 1890 sensu Gauthier & Padian, 1985

Referred Specimens— Tibiae: TTU-P 11393, proximal end of left tibia ( Fig. 7D); TTU-P 11290, proximal end of right tibia ( Fig. 7E, F); TTU-P 11396A, proximal end of right tibia ( Fig. 7G, H); TTU-P 11396B, proximal end of left tibia ( Fig. 7I, J); TTU-P 11412F, proximal end of right tibia ( Fig. 7K, L); TTU-P 11412G, proximal end of right tibia ( Fig. 7M, N); TTU-P 11398, proximal end of left tibia ( Fig. 7O, P); TTU-P 11397B, distal end of right tibia ( Fig. 7Q, R).

Localities— MOTT 3892 (Headquarters); MOTT 3898 (Headquarters South).

Description and Rationale for Assignment— TTU- P11393, TTU-P 11290, TTU-P 11396A-B, TTU-P 11412F- G, and TTU-P 11398 preserve the proximal ends of tibiae as well as portions of the midshafts. There are five distinct morphs of tibiae among these six specimens. TTU-P 11396A ( Fig. 7G, H), TTU-P 11393 ( Fig. 7D), TTU- P11290 ( Fig. 7E, F), and TTU-P 11398 ( Fig. 7O, P) represent distinct morphologies, whereas TTU-P 11412F-G are identical to TTU-P 11396B, and these latter three

specimens are described together ( Fig. 7I–N).

TTU-P 11393 preserves a large portion of the midshaft that is circular in cross section ( Fig. 7D). The proximal end of the tibia is subcircular with a flat posterior border in proximal view. Anteriorly, the tibia is rounded, and there are two posterior condyles that are the same length at their posterior borders. The posterolateral margin of the proximal end appears to be square; however, the lateral posterior condyle is worn, presumably as a result of taphonomy. The proximal surface of the lateral condyle is depressed ( Fig. 7D). This is similar to the condition in Euparkeria and pseudosuchian archosaurs, though the depression in Euparkeria is not to the same degree as in pseudosuchians (Nesbitt 2011; 330:1). The medial posterior condyle is rounded posteromedially, and the medial surface is slightly concave. Because the specimen has a depressed lateral condyle, we assign TTU-P 11393 to Pseudosuchia.

The posterior portion of the proximal end of TTU- P11290 comprises a larger medial condyle and a smaller lateral condyle ( Fig. 7E, F). The posterior border of the condyles is level in proximal view, and the condyles are separated by a small groove on the posterior surface that widens distally to form a fossa ( Fig. 7F). The proximal surface of the lateral condyle is depressed in comparison to the concave medial condyle ( Fig. 7E), which is characteristic of Euparkeria and crocodylian-line archosaurs, though the proximal surface is not as depressed in Euparkeria as it is in pseudosuchians (Nesbitt 2011; 330:1). The posteromedial margin of the proximal end of the tibia is formed by a proximodistally-oriented ridge originating just distal to the medial condyle and continuing onto the midshaft. In proximal view, the anterolateral border is flat and the anteromedial border angles towards the rounded medial condyle ( Fig. 7F). The specimen has a depressed lateral condyle, so we assign TTU-P 11290 to Pseudosuchia.

The midshaft of TTU-P 11396A is elliptical in cross section and is widest in the posteromedial-anterolateral axis ( Fig. 7G, H). TTU-11396A expands slightly towards the proximal end in comparison with the other tibiae, and is rounded anteriorly with a flat lateral border in proximal view ( Fig. 7H). TTU-P 11396A has two posterior condyles on the proximal end. The medial condyle is rounded posteromedially. The lateral condyle of TTU-P 11396A expands posteriorly to a lesser extent than TTU-P 11396B and TTU-P 11412F and is depressed ( Fig. 7G). Again, this is a characteristic of Euparkeria and pseudosuchians, though the proximal surface is not as depressed in Euparkeria as it is in pseudosuchians (Nesbitt 2011; 330:1). The lateral condyle is level with the medial condyle in TTU-P 11396A, and the two condyles are separated by a wide proximodistally-trending groove ( Fig. 7G, H). TTU- P11396A has a round fossa on the posterior surface distal to the medial condyle. The specimen has a depressed lateral condyle, and therefore we assign TTU-P 11396A to Pseudosuchia.

The midshaft of TTU-P 11412F is elliptical in cross section and is widest in the posteromedial-anterolateral axis. TTU-P 11412F-G and TTU-P 11396B are triangular in anterior view and expand greatly from the midshaft to the proximal end ( Fig. 7I–N). Both TTU-P 11412F-G and TTU-P 11396B are rounded anteriorly and have flat lateral borders in proximal view ( Fig. 7J, L, N). TTU- P11412F tapers slightly anterolaterally in proximal view, whereas TTU-P 11396B and TTU-P 11412G are rounded in proximal view. All three specimens have two posterior condyles on the proximal end. The medial condyle in both TTU-P 11412F and TTU-P 11396B is rounded posteromedially, and it is worn in TTU-P 11412G.In TTU-P 11412F-G, the proximal surface of the medial condyle is concave, whereas this surface is obscured by matrix in TTU- P11396B. The proximal surface of the lateral condyle is concave in all three specimens ( Fig. 7I, K, M), again a characteristic of Euparkeria and pseudosuchians, though the proximal surface is not as depressed in Euparkeria as it is in pseudosuchians (Nesbitt 2011; 330:1). The surface between the two concavities on the proximal surface of TTU-P 11412F-G is convex. There is a rounded expansion just anteromedial to the concavity on the surface of the medial condyle in TTU-P 11412F ( Fig. 7K). The lateral condyle in TTU-P 11396B and TTU-P 11412F-G expands posteriorly from the proximal end and is concave proximally ( Fig. 7J, L, N). The lateral condyle is level with the medial condyle in all specimens, and the two condyles are separated by a wide proximodistally-trending groove. The groove is wider and shallower in TTU-P 11396A. The anterior border of the proximal end is angled anterodistally in TTU-P 11412G and TTU-P 11396A. TTU-P 11412F- G and TTU-P 11396B have depressed lateral condyles, so we assign them to Pseudosuchia.

TTU-P 11398 preserves the expanded proximal end of the tibia as well as a small portion of the midshaft ( Fig. 7O, P). The proximal end is flat and preserves two posterior condyles. In proximal view, the medial and posterolateral borders are flat ( Fig. 7P). On the anterior border of the proximal surface, the tibia tapers anteromedially. The anteromedially-tapering portion is distinct from the cnemial crest observed in dinosauromorphs in that it does not form a distinct angle with the shaft of the tibia (Novas 1996). On the posterior border of the proximal surface, the lateral posterior condyle tapers posteriorly and the medial posterior condyle is rounded and forms much of the posterior border( Fig. 7P). There is a distally-trending groove separating the posterior condyles that extend from the proximal surface onto the midshaft distally. In proximal view this groove appears as a small concavity between the posterior condyles. The posterior condyles are level at their posterior borders. The lateral posterior condyle forms a rounded ridge on the posterolateral surface that does not extend distally onto the midshaft. The anteromedially-tapering portion forms a sharp ridge on the anterior surface of the proximal end of the tibia that extends distally onto the midshaft. The lateral and medial posterior condyles are depressed distally. A depressed lateral condyle on the proximal surface of the tibia is a characteristic of Euparkeria and pseudosuchian archosaurs, though the proximal surface is not as depressed in Euparkeria as it is in pseudosuchians (Nesbitt 2011; 330:1), and based on this character state, we assign TTU-P 11398 to Pseudosuchia.

TTU-P 11397B preserves the distal end of a right tibia as well as a portion of the midshaft ( Fig. 7Q, R). The tibia is hollow, and the midshaft is convex medially and slightly concave laterally because of a groove on the lateral surface ( Fig. 7Q). This groove is present in most crocodylian-line archosaurs (Nesbitt 2011; 337:1). The distal end of the tibia expands anteroposteriorly and preserves two articular surfaces for the astragalus. The distally rounded posterolateral surface is extended further distally than the distally concave anterolateral surface, identical to the condition in Effigia Nesbitt and Norell, 2006 (Nesbitt 2007: fig. 45). The anterolateral articular surface slants medially, whereas the posterolateral articular surface slants laterally as in shuvosaurids, Postosuchus , stagonolepidids, and crocodylomorphs (Nesbitt 2007). We therefore assign TTU-P 11397B to Pseudosuchia based on the presence of a groove on the lateral surface.

AETOSAURIA Marsh, 1884 sensu Parker, 2007

SCUTARX DELTATYLUS Parker, 2016a

Referred Specimen— TTU-P 10195, left paramedian osteoderm ( Fig. 8A–C).

Locality— MOTT 3899 (Headquarters NW).

Description and Rationale for Assignment— TTU- P10195 is incomplete but still possesses diagnostic character states allowing a precise taxonomic assignment ( Fig. 8A–C). The weakly-raised anterior bar and a radial ornamentation of grooves and ridges ( Fig. 8B) allow assignment as a non-desmatosuchin desmatosuchine aetosaur (Parker 2016a; 52:2, 53:1). This specimen is a paramedian osteoderm, as it is mediolaterally longer than anterolaterally wide, and an anteromedial projection of the anterior bar places this osteoderm on the left side of the carapace. No distinct pitting is present as ornament surrounding the eminence. The osteoderm is dorsoventrally-thickened with a slight ventral strut similar to that found in Calyptosuchus wellesi Long and Ballew, 1985 , Scutarx deltatylus , and typothoracisine aetosaurs (Martz 2002; Parker 2016a; 56:1). A prominent dorsal

Figure 9. A–N. Paracrocodylomorph femora in medial (A), proximal (B), posterior (B, E, G, I, K, M), and distal (D, F, H, J, L, N) views. A, B. TTU-P 11411E. C, D. TTU-P 11409A. E, F. TTU-P 11409B. G, H. TTU-P 11048. I, J. TTU-P 11283. K, L. TTU-P 11284. M, N. TTU-P 10845. O–X. Shuvosaurid femora in medial (O, Q, S, U, W) and proximal (P, R, T, V, X) views. O, P. TTU-P 11411A. Q, R. TTU-P 11411B. S, T. TTU- P11411C. U, V. TTU-P 11402. W, X. TTU-P 11272. Scale bar 1 cm. Abbreviations: alt, anterolateral tuber; amt, anteromedial tuber; ctf, crista tibiofibularis; g, groove; lc, lateral condyle; mc, medial condyle; p, pit; pmt, posteromedial tuber. Arrows point anteriorly.

eminence that does not contact the posterior margin of the plate ( Fig. 8B) and a slightly beveled posterior margin are characteristics of paratypothoracisin aetosaurs ( Heckert and Lucas 2000, Martz and Small 2006, Parker 2007, Parker 2016a; 54:0, 55:1). The posteromedial corner of the plate preserves a raised triangular rugose protuberance ( Fig. 8A, B) that is autapomorphic for S.deltatylus (Parker 2016a, b). The ventral surface is smooth ( Fig. 8C) with the exception of a series of longitudinal striations near the posterior margin, which is present in most aetosaurs, and is the area that dorsally overlaps the anterior margin of the subsequent plate (Parker 2008). Two small foramina are present in the slight ventral surface emargination ventral to the dorsal eminence. The dorsoventral thickening, anteriorly-situated eminence, and the triangular raised rugose posteromedial margin suggest this plate is from the anterior trunk region. The presence of the triangular protuberance at the posteromedial margin allows assignment of this specimen to S. deltatylus (Parker 2016a, b).

PARACROCODYLOMORPHA Parrish, 1993 sensu Weinbaum and Hungerbühler, 2007

Referred Specimens— Femora: TTU-P 11411E, proximal end of right femur (Fig. 9A, B); TTU-P 11409A, distal end of left femur (Fig. 9C, D); TTU-P 11409B, distal end of right femur (Fig. 9E, F); TTU-P 11048, distal end of left femur (Fig. 9G, H); TTU-P 11283, distal end of left femur (Fig. 9I, J); TTU-P 11284, distal end of left femur (Fig. 9K, L); TTU-P 10845, distal end of left femur (Fig. 9M, N).

Localities— MOTT 3898 (Headquarters South); MOTT 3902 (Lower Far East).

Description and Rationale for Assignment— TTU- P11411E comprises the expanded proximal end of a right femur (Fig. 9A, B). The proximal surface of the femur is convex and has a small pit (Fig. 9B) that may correspond to the anteroposteriorly-trending groove present in shuvosaurids (Nesbitt 2011; 314:1). The anterior portion of the femoral head is expanded anteriorly but does not project markedly from the shaft (Fig. 9A). The anterior surface is flat, and the medial surface bears an expansion with two distinct, medially-rounded tubera (anterior and posterior). These tubera are separated by a shallow groove and are equal in size (Fig. 9B). The anteromedial and posteromedial tubera are similar in size to crocodylomorphs and most taxa previously categorized as ‘rauisuchians’ (e.g., rauisuchids and poposauroids) (Nesbitt and Stocker 2008). The lateral margin is concave in proximal view, and there is a small, anterolaterallyrounded anterolateral tubera (Fig. 9B). The presence of three tubera is characteristic of all suchians (Nesbitt 2011; 300–302). The area where a proximal condylar fold might be present is worn and therefore prevents a more specific assignment of TTU-P 11411E (e.g., to Crocodylomorpha; see Nesbitt et al. 2006). Therefore we assign this specimen to Paracrocodylomorpha.

TTU-P 11409A-B, TTU-P 11048, TTU-P 11283, TTU- P11284, and TTU-P 10845 preserve the distal ends of femora and portions of the midshafts (Fig. 9C–N). These specimens are nearly identical and are described together with differences noted. In cross section, the shaft is rounded laterally and tapers medially to varying degrees. The femur is anteriorly convex and posteriorly concave in distal view. The distal end of the femur preserves three condyles, a large, posteriorly-rounded medial, tibial condyle, a small, posterolaterally-tapering lateral, fibular condyle, and a laterally-rounded crista tibiofibularis (Fig. 9D, F, H, J, L, N). The crista tibiofibularis is separated from the lateral condyle by a deep groove on the distal surface, a character state present in dinosauromorphs, Effigia , Poposaurus , Fasolasuchus Bonaparte, 1981 , Postosuchus , and crocodylomorphs (Parker and Irmis 2005: pg. 52; Nesbitt 2011; 322:1). The angle between the lateral condyle and crista tibiofibularis in distal view is about 90° in these specimens, a character shared by Effigia , Batrachotomus , Fasolasuchus , Postosuchus , and crocodylomorphs (Nesbitt 2011; 319:1). The intercondylar groove is deep on the posterior surface in all specimens and continues onto the distal end of TTU-P 11284 and TTU-P 11283 (Fig. 9D, F, H, J, L, N). In the smaller TTU-P 11284 and TTU-P 10845 the posterolateral margin of the distal end is formed by a proximodistally-oriented ridge (Fig. 9K, M). In the larger TTU-P 11048, this posterolateral margin is formed by a flattened surface that originates between the lateral condyle and crista tibiofibularis and extends proximally (Fig. 9G). TTU-P 11283 and TTU-P 11409A-B are not preserved well enough to describe this feature. The anteromedial border is similar in TTU-P 11284 and TTU-P 409A, whereas TTU-P 11048 and TTU-P 11283 preserve a proximodistally-oriented groove just proximal to the medial condyle. The combination of the presence of a groove and the 90° angle between the crista tibiofibu- laris and lateral condyle supports assignment of these specimens to Paracrocodylomorpha.

POPOSAUROIDEA Nopsca, 1928 sensu Weinbaum & Hungerbühler, 2007

SHUVOSAURIDAE Chatterjee, 1993 sensu Nesbitt, 2007

Referred Specimens— Femora: TTU-P 11411A, proximal end of left femur (Fig.9O,P); TTU-P 11411B, proximal end of left femur (Fig. 9Q, R); TTU-P 11411C, proximal end of left femur (Fig. 9S, T); TTU-P 11402, proximal end of left femur (Fig. 9U, V); TTU-P 11272, proximal end of right femur (Fig. 9W, X).

Localities— MOTT 3898 (Headquarters South); MOTT 3899 (Headquarters NW).

Description and Rationale for Assignment — TTU -P11402, TTU-P 11272, and TTU-P 11411A-C preserve the femoral head and the uncrushed proximal portion

of the femoral shaft (Fig. 9O–X). The femora are nearly identical and are subsequently described together with any differences noted. The broken cross-section of the femur reveals that the midshaft is ovate and hollow. The proximal surface of the femur possesses a prominent anteroposteriorly-trending groove (Fig. 9P, R, T, V, X) as in the dinosauriform Eucoelophysis Sullivan and Lucas, 1999 and shuvosaurids, though this character is not restricted to these taxa (Nesbitt 2011;314:1). The posterior portion of the proximal surface of the femur slopes posteromedially as in theropods and the anterior portion of the femoral head projects markedly from the shaft providing a distinct neck (Fig. 9O, Q, S, U, W). However, there is no pronounced ligament sulcus on the ventral surface of the femoral head and therefore it is not “offset” in the same manner as in members of Dinosauria (Novas 1992; character 11). The anteromedial and posteromedial tubera are separated by a pronounced sulcus in TTU-P 11402 and TTU-P 11411B-C (Fig. 9Q–V). TTU-P 11272 and TTU- P11411A are worn and missing both of the medial tubers, although broken areas show that they were present (Fig. 9O, P, W, X). The anteromedial tuber has a posteriorly-projecting apex that forms a hook in proximal view. This hook is most evident in TTU-P 11402 and TTU-P 11411B (Fig. 9R, V), and is a character shared by Effigia and Shuvosaurus Chatterjee, 1993 (Nesbitt 2011; 300:3). The lateral margin is slightly convex in proximal view and there is no distinct anterolateral tuber (Fig. 9P, R, T, V, X) as in most pseudosuchian archosaurs (Nesbitt 2011; 302:1). These are all characteristics of shuvosaurids (Nesbitt 2007: fig. 44, Nesbitt 2011: fig. 38). The medial surface of the shaft lacks the distinct ridge or trochanter found in Arizonasaurus Welles, 1947 and Effigia (Nesbitt 2005: fig. 26, 2007: fig. 44). Nevertheless, these specimens cannot be assigned to a specific genus and therefore we assign the listed partial femora to Shuvosauridae .

ORNITHODIRA Gauthier, 1986 =AVEMETATARSALIA Benton, 1999 DINOSAUROMORPHA Benton, 1985 sensu Sereno, 1991

Referred Specimens— Tibiae: TTU-P 11412A, proximal end of right tibia ( Fig. 10A, B); TTU-P 11412E, proximal end of left tibia ( Fig. 10C, D).

Locality— MOTT 3898 (Headquarters South).

Description and Rationale for Assignment— TTU -P11412A and E preserve the proximal ends of tibiae and portions of the midshafts ( Fig. 10A–D). The specimens are nearly identical and therefore described together, noting any differences. The proximal end is flat

and preserves a cnemial crest anteriorly. TTU-P 11412A preserves two posterior condyles that taper posteriorly and are equal in size, and the medial posterior condyle is worn in both TTU-P 11412A and E ( Fig. 10B, D). Because the medial posterior condyle is worn, we cannot tell if the posterior condyles are level at their posterior borders. The posterior border is concave between the posterior condyles in TTU-P 11412A ( Fig. 10B). The lateral posteri- or condyle is separated from the cnemial crest by a groove on the lateral surface that extends from the proximal end onto the midshaft ( Fig. 10A). The groove does not extend further distally, and the medial surface of the midshaft is flat and featureless. The cnemial crest tapers anteriorly and forms a rounded ridge on the anterior surface of the proximal end of the tibia that extends distally onto the midshaft ( Fig. 10A, C). An anteriorly-tapered cnemial crest is a characteristic of Avemetatarsalia (Novas 1996; 10:1), and an anteriorly straight cnemial crest is a characteristic of non-dinosaurian dinosauromorphs (Nesbitt 2011; 328:1). Therefore, we assign TTU-P 11412A and E to Dinosauromorpha.

LAGERPETIDAE Arcucci, 1986 sensu Nesbitt et al., 2009c

Referred Specimens— Femora: TTU-P 11877, proximal end of right femur ( Fig. 10E, F); TTU-P 11282, proximal end of right femur ( Fig. 10G, H); TTU-P 10866, distal end of left femur ( Fig. 10I–K).

Locality— MOTT 3898 (Headquarters South).

Description and Rationale for Assignment— TTU- P11877 and TTU-P 11282 preserve the proximal ends of right femora and portions of the midshaft ( Fig. 10E–H). They were briefly described by Nesbitt et al. (2009c: pg. 508) and assigned to Lagerpetidae . These specimens are identical and are described together. The proximal surface of the femur is convex and smooth. The anterior portion of the femoral head projects from the shaft with a smooth transition, and the femoral head is hook shaped in medial and lateral views ( Fig. 10E, G).This is characteristic of lagerpetid dinosauromorphs ( Irmis et al. 2007 a; Nesbitt et al. 2009c; Nesbitt 2011; 306:1). The medial surface of the femur is smooth except for the small, worn, medially-projecting posteromedial tuber at the proximal end ( Fig. 10F, H), also shared by lagerpetids (Nesbitt et al. 2009c). The lateral margin is convex anteriorly at the small anteromedial tuber and concave posteriorly. The anterior border of the femur is rounded in proximal view at the small, rounded anteromedial tuber ( Fig. 10F, H). A small anteromedial tuber is characteristic of all avemetatarsalians (Nesbitt 2011: pg. 146). The posterior border of the shaft is a sharp, proximodistally-trending ridge, a character of many dinosauriforms (Nesbitt 2011; 301:1). The posterolateral surface of the proximal end is lower distally than the anterolateral portion of the proximal surface of the femur, a dinosauromorph character state (Nesbitt 2011; 313:1). TTU-P 11877 and TTU-P 11282 do not have an anterior trochanter or a trochanteric shelf, unlike the condition in Dromomeron gregorii (Nesbitt et al. 2009c: fig. 2), although the development of the anterior trochanter and trochanteric shelf is ontogenetically variable in dinosauromorphs (Nesbitt et al. 2009 c, Griffin and Nesbitt 2016a, b). We are unable to assign TTU-P 11877 and TTU-P 11282 to Lagerpeton Romer, 1971 , Ixalerpeton Cabreira et al. 2016 , or D. romeri Irmis et al., 2007 a and therefore we assign both specimens to Lagerpetidae .

TTU-P 10866 preserves the robust distal end of a femur that gradually expands distally from the shaft and was briefly assigned to Lagerpetidae by Nesbitt et al. (2009c: pg. 508) ( Fig. 10I–K). The anterior surface of TTU-P 10866 preserves a mediolaterally-oriented ridge that arcs proximally onto the lateral side of the femur. The ridge separates unfinished bone (dorsally) from finished bone (ventrally) ( Fig. 10K), and Nesbitt et al. (2009c) identify this ridge as the distal origin of the M. femorotibialis externus . The medial surface is flat in the specimen, and the anteromedial corner is obtuse ( Fig. 10J). In distal view, the anterior edge of TTU-P 10866 is sigmoidal. The crista tibiofibularis is as large as the medial, tibial condyle in the specimen and is separated from the lateral, fibular condyle on the distal surface by a distinct groove ( Fig. 10J). The presence of a large crista tibiofibularis places TTU-P 10866 within Lager- petidae (Nesbitt 2011; 326:1). The medial condyle of the specimen is robust and square in distal view and the lateral condyle is gracile and rounded. The distal articular surface of the lateral condyle of TTU-P 10866 is covered with small grooves and ridges. Based on the morphology of the crista tibiofibularis, we assign TTU- P10866 to Lagerpetidae .