Dromomeron romeri Irmis et al., 2007b

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

Dromomeron romeri Irmis et al., 2007b

AGE: Mid to late Norian ( Litwin et al., 1991; Lucas, 1998a; Heckert et al., 2005; Parker, 2007; Irmis et al., 2007a)

OCCURRENCE: Site 3, Hayden Quarry, Ghost Ranch, Rio Arriba County, New Mexico.

HOLOTYPE: GR 218, left femur.

PARATYPES: A right femur, GR 219, and a left tibia, GR 220, may belong to the same individual as the holotype. Additional material includes GR 221, a partial left femur; GR 234, a complete right femur; GR 222, a complete left tibia; and GR 223, a complete astragalocalcaneum.

REFERRED MATERIAL: GR 235, partial articulated skeleton; GR 236, isolated right tibia (cnemial crest crushed); NMMNH P- 35379, complete astragalocalcaneum; AMNH FR 2721, distal portion of a femur; AMNH FR 30648, distal portion of a right tibia; AMNH FR 30649, distal portion of a right tibia.

REMARKS: Irmis et al. (2007a) named and briefly described Dromomeron romeri , the first non-dinosaurian dinosauromorph discovered since Lagerpeton . The holotype femur bears characters that were thought to be autapomorphies of Lagerpeton . The discovery of Dromomeron in the Norian of North America, along with nondinosaurian dinosauriforms and dinosaurs, shows that primitive dinosauromorphs coexisted with dinosaurs. Only hind limb elements are known from this taxon at present.

Dromomeron romeri differs from Dromomeron gregorii and all other basal dinosauromorphs in possessing the following autapomorphies: (1) absence of a fourth trochanter; (2) presence of a sharp ridge on the anteromedial edge of the distal end of the femur; (3) presence of a lateral tuberosity on the anterolateral edge of the distal end of the femur; and (4) a large crest on the anteromedial edge of the astragalus and associated anteromedial concavity on the distal tibia.

KEY REFERENCES: Irmis et al., 2007a; Nesbitt et al., 2009b.