Lesothosaurus dianosticus Galton, 1978

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 : 50-51

Lesothosaurus dianosticus Galton, 1978

(fig. 12B–C)

AGE: Hettangian-Sinemurian, Early Jurassic ( Olsen and Galton, 1984).

OCCURRENCE: Upper Elliot Formation, South Africa and Lesotho.

SYNTYPES: BMNH RUB17, mostly disarticulated remains of at least two individuals, one larger than the other, including most of one articulated skull; BMNH RUB 23, partial skull, nearly complete, disarticulated skull; BMNH R11004, partially articulated posterior skull and anterior neck, including the braincase, parietals, right squamosal, right quadrate, posterior portion of the right lower jaw, axis and third cervical, partial postcranium ; SAM-PK-K401, partial postcranium, including proximal ischia, partial postcranium, including proximal ischia.

REMARKS: Lesothosaurus was first described by Galton (1978) for well-preserved crania and postcrania from the upper Elliot Formation. Sereno (1991a) added further details to Galton’s (1978) original description, and assigned other material to the taxon. All basal dinosaur and ornithischians analyses agree that Lesothosaurus is one of the basalmost ornithischians. Only Butler et al. (2008b) found heterodontosaurids more basal than Lesothosaurus and found Lesothosaurus as the sister taxon to all thyreophorans.

Butler (2005) provided the following diagnosis for Lesothosaurus : anterior premaxillary foramen present; slot in maxilla for lacrimal present; six premaxillary teeth pres- ent; absence of diastema between the premaxillary and maxillary teeth; maxillary teeth lack apicobasally extending ridges on their lingual and labial faces; manual phalanges lacking prominent intercondylar processes; ilium with well-developed supraacetabular flange and ventromedially angling brevis shelf visible in lateral view; dorsal groove on the ischial shaft present; shaft of ischium twists through 90 ° along its length, forms an elongate symphysis with the opposing ischial blade, and lacks a tab-shaped obturator process; prepubic process short and mediolaterally flattened rather than rodlike and does not extend beyond the end of the preacetabular process of the ilium; postcranial osteoderms absent.

KEY REFERENCES: Thulborn, 1970, 1972; Santa Luca, 1984; Norman et al., 2004; Butler, 2005.