A new specimen of Helicoprion Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function

作者：Lebedev O A^*

来源：Acta Zoologica, 2009, 90: 171-182.

DOI：10.1111/j.1463-6395.2008.00353.x

• Lower Permian
• Artinskian
• Helicoprion
• dentition

A new Helicoprion bessonowi Karpinsky, 1899 ( Chondrichthyes, Eugeneodontiformes) specimen from the Artinskian of Kazakhstan is described. This is the southernmost occurrence of this species in the Cisurals area. Its presence suggests a biogeographical link for this species between the Cisurals and Japan. Residue obtained from chemical preparation of the sample included numerous scales and several teeth, which are tentatively assigned to Helicoprion. This assumption is based upon morphological similarity of the scales to those known in other eugeneodontiforms. Campodus-like teeth might be part of the lateral dentition of Helicoprion. A new reconstruction of the interaction of the lower tooth whorl with the upper jaw dentition is suggested and its function is discussed. It is proposed that there was no symphysial whorl in the upper jaw but its role was played by a rigid cover formed by a series of small teeth at the palatoquadrates. Microscopic study of the tooth crown surface revealed scratch marks, which might have resulted from pressing the food object against the upper jaw. Using extant odontocetans as an ecological model led to a conclusion that helicoprionids most likely fed on cephalopods and to some extent on fish. This assumption is based upon the concentration of functional dentition in the area of the lower jaw symphysis in both groups of animals.

• 出版日期2009-5