A new species of Zangerlia (Testudines: Nanhsiungchelyidae) from the Upper Cretaceous redbeds at Bayan Mandahu, Inner Mongolia, and the relationships of the genus

Abstract

Zangerlia neimongolensis sp.nov. is described on the basis of material from the Upper Cretaceous redbeds at Bayan Mandahu in Inner Mongolia. Zangerlia neimongolensis is similar to Zangerlia testudinimorpha in the proportions of the carapace and plastron and presence of a knob at the posterior end of the neural series, but differs from it in the arrangement of scutes covering the bridge. The placement of Zangerlia in the Nanhsiungchelyidae is supported by derived features of the bridge peripherals and plastral scutes shared by Z. neimongolensis, Basilemys, and Nanhsiungchelys. These are the presence of ventrally expanded sixth inframarginal scutes, humeral scutes that are narrow at the midline and expanded laterally, pectoral scutes that are wide at the midline and narrow laterally, and large rectangular abdominal scutes. The skull of Zangerlia is more primitive than that of Nanhsiungchelys, the only other member of the family for which a skull is known. It shows extensive emargination of the temporal and cheek regions and the absence of a large, tubular external narial opening. A cladistic analysis of the Trionychoidea using Zangerlia as the representative of the Nanhsiungchelyidae suggests a sister-group relationship between the Nanhsiungchelyidae and Adocidae.