Tchoiria klauseni, KSEPKA & GAO & NORELL, 2005

KSEPKA, DANIEL T., GAO, KE-QIN & NORELL, MARK A., 2005, A New Choristodere from the Cretaceous of Mongolia, American Museum Novitates 3468 (1), pp. 1-23 : 3

Tchoiria klauseni , new species

HOLOTYPE: The holotype ( IGM 1 /8) consists of an incomplete skull and partial disarticulated postcranial skeleton. The following elements are preserved: a skull nearly complete on the right side and fragmentary on the left, missing the tip of the snout and distorted in the braincase region; partial right dentary and splenial in articulation; five cervical, six dorsal, three sacral, and four caudal vertebrae or vertebral elements; several ribs and gastralia; right coracoid, fragment of scapular blade; right radius, right ulna; right ilium, partial right ischium, partial right pubis; right femur.

ETYMOLOGY: Named in honor of James Klausen, the preparator of the holotype, in recognition of years of dedicated volunteer service to the American Museum of Natural History .

TYPE LOCALITY AND HORIZON: The type locality is Two Volcanoes (43°49.503̍N, 99°19.546̍E; fig. 3). The fossil beds at Two Volcanoes are composed of light­colored fine sands interbedded with coarser sands. The age of this locality has not been firmly established; however, the freshwater invertebrate fauna and the presence of spatulate sauropod teeth suggest an Early Cretaceous Aptian age roughly equivalent to beds of the ‘‘Hütheg Svita’’ ( Shuvalov, 2000). A more well­constrained age for Two Volcanoes awaits further work .

DIAGNOSIS: Tchoiria klauseni can be differentiated from the type species T. namsarai by the smaller number of teeth in the maxilla and the symphyseal portion of the dentary. There are slightly more than 34 teeth in the maxilla of T. klauseni while there are more than 60 in the maxilla of T. namsarai . There are 12 teeth in the symphyseal portion of the dentary in T. klauseni and 17 teeth in the symphyseal portion of the dentary in T. namsarai .