Lagerpeton chanarensis Romer, 1971a

Nesbitt, Sterling J., 2011, The Early Evolution Of Archosaurs: Relationships And The Origin Of Major Clades, Bulletin of the American Museum of Natural History 2011 (352), pp. 1-292 : 44

Lagerpeton chanarensis Romer, 1971a

AGE: Ladinian, Middle Triassic ( Rogers et al., 2001).

OCCURRENCE: Chañares Formation, Argentina.

HOLOTYPE: UNLR 06, articulated right hind limb.

REFERRED MATERIAL: PVL 4619, articulated sacrum, pelvis, and partial right and left hind limbs; PVL 4625, articulated vertebral column including dorsal, sacral, and anterior caudal vertebrae, left pelvis, and left femur; PVL 5000, proximal left femur; MCZ 4121, partial right and left femora.

REMARKS: Lagerpeton was named for a hind limb ( Romer, 1971a), and referred material consists of the pelvic girdle and posterior presacral, sacral, and proximal caudal vertebrae ( Bonaparte, 1984; Arcucci, 1986; Sereno and Arcucci, 1994a). In the most recent review of the taxon, Sereno and Arcucci (1994a) provided a detailed description of the hind limb and highlighted synapomorphies shared with dinosauriforms. Therefore, Lagerpeton possesses an important mix of plesiomorphic archosaurian character states and derived dinosaurian characters.

Lagerpeton , Dromomeron romeri , and Dromomeron gregorii form the Lagerpetidae ( Nesbitt et al., 2009b) at the base of Dinosauromorpha. Consequently, most of the unique features of the femur, tibia, and ankle of Lagerpeton cited by Sereno and Arcucci (1994a) are now synapomorphies of Lagerpetidae. The thin, aliform ridge for the attachment of the caudifemoralis musculature (5 fourth trochanter) differentiates Lagerpeton from both D. romeri and D. gregorii .

KEY REFERENCES: Romer, 1971 a, 1972a; Bonaparte, 1984; Arcucci, 1986; Sereno and Arcucci, 1994a.