Marasuchus lilloensis ( 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 : 45-46

Marasuchus lilloensis ( Romer, 1971a) , sensu

Sereno and Arcucci, 1994b

5 Lagosuchus lilloensis Romer, 1971a

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

OCCURRENCE: Chañares Formation, Argentina.

HOLOTYPE: PVL 3871, partial articulated skeleton including the posterior portion of the vertebral column (from the last dorsal vertebra to the 25th caudal vertebra), left scapulocoracoid, humerus, radius, ulna, fragmentary right pelvis, left ilium, left pubis, partial right and left hind limbs.

REFERRED MATERIAL: PVL 3870, partial skeleton including the maxilla and partial braincase, vertebral column from the atlas to the anterior caudal vertebrae, articulated pelvis and hind limbs lacking only the distal phalanges and unguals; PVL 3872, partial braincase and articulated vertebral column from the atlas to the ninth presacral vertebra; PVL 4670, articulated anterior caudal vertebrae with chevrons; PVL 4671, articulated anterior caudal vertebrae with chevrons; PVL 4672, articulated vertebral column from atlas to the 17th presacral vertebra.

REMARKS: Romer (1971 a, 1972a) described two incomplete long-limbed forms from the Middle Triassic of Argentina, ‘‘ Lagosuchus talampayensis ’’ (UNLR 09) as the genotype and ‘‘ Lagosuchus ’’ lilloensis (PVL 3871) as a second species. Sereno and Arcucci (1994b) demonstrated that the holotype of ‘‘ Lagosuchus talampayensis ’’ (UNLR 09) is not diagnostic, but referred specimens of ‘‘ Lagosuchus talampayensis ’’ as well as ‘‘ Lagosuchus ’’ lilloensis (PVL 3871) are diagnosable. Therefore, Sereno and Arcucci (1994b) coined a new genus-level taxon, Marasuchus , to replace the nondiagnostic Lagosuchus . Subsequent workers followed Sereno and Arcucci (1994b) in this taxonomic usage.

Marasuchus holds a critical phylogenetic position as a proximal outgroup to Dinosauria in a number of studies ( Sereno and Arcucci, 1994b; Novas, 1996; Benton, 1999; Irmis et al., 2007a). The anatomy was well documented by Bonaparte (1975) and Sereno and Arcucci (1994b). Unfortunately, most of the skull and the manus are missing. Here, I rely almost exclusively on PVL 3870 and 3871 for scoring.

Rauhut (2003) proposed the following characters autapomorphies of Marasuchus : (1) posterior cervical neural spines project anterodorsally; and (2) neural spines of midto posterior dorsal vertebrae contact each other dorsally.

KEY REFERENCES: Romer, 1971 a, 1972a; Bonaparte, 1975; Sereno and Arcucci, 1994b.