Avimimus portentosus Kurzanov, 1981

Age . Santonian-Campanian.

Occurrence. Djadochtan Svita, Omnogov, Ovorkhangai, Mongolia.

Diagnosis. Pleurocoels in mid-cervical vertebrae on mid-length of vertebral centrum, behind the parapophyses; ectepicondyle of humerus significantly expanded anteroposteriorly.

Remarks. Avimimus is a very interesting, but unfortunately also problematical small theropod from the Upper Cretaceous of Central Asia. In his detailed description of the holotype, Kurzanov (1987) referred a partial skull, several vertebrae, an ischium, and a pair of articulated ilia to the same taxon. However, there is some uncertainty as to whether all these elements really represent a single taxon (Novacek 1996, p. 251; Unwin, pers. comm. 1998). Based on my own observations on a cast of the material (ROM 46144), the vertebrae are thought to represent a single taxon or even a single individual, because of their closely corresponding morphology and size, and the cranial remains also correspond well in size with the rest of the material. Thus, pending a revision of the taxon, all the material is provisionally regarded as representing a single species here.

Even if the association of the material is provisionally accepted, a comment on the anatomy of the animal should be made. Kurzanov (1987) reconstructed Avimimus with a short, bird-like tail, although no sacral or caudal vertebrae are known. However, the well-developed fourth trochanter on the femur (the insertion of the m. caudofemoralis longus) and the long presacrai vertebral column make this reconstruction seem rather unlikely.