Scutellosaurus lawleri Colbert, 1981

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 : 51

Scutellosaurus lawleri Colbert, 1981

AGE: Simmurian-Pliensbachian, Early Jurassic ( Peterson and Pipiringos, 1979).

OCCURRENCE: Silty facies of the Kayenta Formation, Rock Head and other nearby localities (e.g., Gold Spring), northern Arizona ( Colbert, 1981).

HOLOTYPE: MNA 175, nearly complete, associated skeleton including the dentitionbearing parts of the skull, cervical, dorsal, sacral, and caudal vertebrae, hundreds of osteoderms, much of the pectoral and pelvic girdles, and portions of the fore- and hind limbs.

REFERRED MATERIAL: MNA 1752, partial disarticulated skeleton; UCMP 130580; UCMP 170829; TMM 43687-16 ; MCZ 8592; MCZ 8799.

REMARKS: Scutellosaurus is one of the better-known basal ornithischians, known from at least 10 partial skeletons. All specimens originate from a small set of localities in the silty facies of the Kayenta Formation. Scutellosaurus was consistently found as one of the earliest undoubted members of Thyreophora in phylogenetic analyses of ornithischians ( Sereno, 1999; Norman et al., 2004; Butler et al., 2008b). As stated by Irmis et al. (2007b), Scutellosaurus is the oldest confirmed ornithischian in North America.

Autapomorphies listed by Butler et al. (2008b) include: dorsal and ventral margins of the preacetabular process of the ilium are drawn out medially into distinct flanges that converge upon one another anteriorly; elongate tail of comprising at least 58 caudal vertebrae.

KEY REFERENCES: Colbert, 1981; Rosenbaum and Padian, 2000; Butler et al., 2008b.