June 21 , 2016

Two Middle Jurassic mammaliaforms, Itatodon Lopatin et Averianov, 2005 and Paritatodon Martin et Averianov, 2010 have been considered to be members of the Docodonta. Detailed comparison of their dental morphologies with that of typical docodonts shows clearly the differences in cusp pattern and cusp-crest relationship of their lower molar crowns. In docodonts, four crests, originating from the apex of cusp a, extend respectively toward cusps b, g, c, and d, and meet the crests therefrom; all the major crests point to the center of cusps. In contrast, in Itatodon and Paritatodon, only two crests from cusp a extend to cusps g and c, and all the crests reconcile to the anterior or posterior cusp surface. Such differences suggest that the docodont molars function mainly by cutting and crushing, whereas those of Itatodon and Paritatodon have a clear shearing function. Both the morphological features and possible molar occlusal function of Itatodon and Paritatodon distinguish them from the typical docodonts and indicate their shuotheriid affinities. Moreover, the term “pseudotalonid” is used in describing the non-homologous dental features, representing different occlusal relationships, in Shuotheridia and Docodonta. It should thus better be restricted in the description of lower dentition of Shuotheridia, as proposed by the original study. Key words: Itatodon, Paritatodon, Middle Jurassic, pseudotalonid, Docodonta, Shuotheridia. Yuan-Qing Wang [wangyuanqing <at> ivpp.ac.cn] and Chuan-Kui

Wang, Y.-Q. and Li, C.-K. (2016)
Reconsideration of the systematic position of the Middle Jurassic mammaliaforms Itatodon and Paritatodon.
Palaeontologia Polonica 67: 249–256.
doi: 10.4202/pp.2016.67_249