A NEW SPECIES OF CLEVOSAURUS (LEPIDOSAURIA: RHYNCHOCEPHALIA) FROM THE UPPER TRIASSIC OF RIO GRANDE DO SUL, BRAZIL

Abstract:  Well-preserved cranial remains of a small sphenodontian lepidosaur from the Upper Triassic Caturrita Formation of Rio Grande do Sul, Brazil, are the first record of the genus Clevosaurus Swinton, 1939 from South America. They represent a new species, Clevosaurus brasiliensis , which is distinguished by a very short antorbital region of the skull (corresponding to about 20 per cent of skull length) and the presence of teeth in addition to two longitudinal rows on the pterygoid. C. brasiliensis most closely resembles C. bairdi from the Lower Jurassic of Nova Scotia (Canada) and C. mcgilli from the Lower Jurassic of Yunnan (China). The discovery of Clevosaurus in the Upper Triassic of southern Brazil provides a significant range extension of this widely distributed sphenodontian genus. Along with other recent finds, it also suggests that there may have been less biotic provincialism among terrestrial vertebrates during the Late Triassic than has previously been assumed.