Arstanosaurus

Abstract: The hadrosaurid dinosaur Arstanosaurus akkurganensis was described on the basis of the posterior end of a left maxilla, an associated distal end of a femur and an unreported isolated tooth, all of which were collected from the Akkurgan locality. East of the Aral Sea in central Kazakhstan. Redescription of the type material reveals that the material was inaccurately described, appears to lack specifically diagnostic characters and, although it can be assigned tentatively to the hadrosaurid subfamily Lambeosaurinae on the basis of the form of the caudodorsal margin of the maxilla, should for taxonomic purposes be regarded as a nomen dubium . Arstanosaurus cannot be assigned to any known hadrosaurid taxon from Kazakhstan with any confidence at present partly because of a lack of comparative material, and difficulties of comparative dating across what appear to be very similar localities (e.g. Shakh-Shakh). Broad anatomical similarities can be drawn with the Chinese genus Bactrosaurus . Additional hadrosaurid material collected from Baynshin Tsav, Mongolia, previously attributed to the genus Arstanosaurus , represents two new ornithopod taxa assignable to the subfamilies Hadrosaurinae and Lambeosaurinae. General comparison between the forms collected from Akkurgan, Iren Nor (China) and Baynshin Tsav supports the contention that all three localities may be dated as Early Senonian (Coniacian-Santonian) in age.