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11 October 2013 Vertebral Morphology, Dentition, Age, Growth, and Ecology of the Large Lamniform Shark Cardabiodon ricki
Michael G. Newbrey, Mikael Siversson, Todd D. Cook, Allison M. Fotheringham, Rebecca L. Sanchez
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Abstract

Cardabiodon ricki and Cardabiodon venator were large lamniform sharks with a patchy but global distribution in the Cenomanian and Turonian. Their teeth are generally rare and skeletal elements are less common. The centra of Cardabiodon ricki can be distinguished from those of other lamniforms by their unique combination of characteristics: medium length, round articulating outline with a very thick corpus calcareum, a corpus calcareum with a laterally flat rim, robust radial lamellae, thick radial lamellae that occur in low density, concentric lamellae absent, small circular or subovate pores concentrated next to each corpus calcareum, and papillose circular ridges on the surface of the corpus calcareum. The large diameter and robustness of the centra of two examined specimens suggest that Cardabiodon was large, had a rigid vertebral column, and was a fast swimmer. The sectioned corpora calcarea show both individuals deposited 13 bands (assumed to represent annual increments) after the birth ring. The identification of the birth ring is supported in the holotype of Cardabiodon ricki as the back-calculated tooth size at age 0 is nearly equal to the size of the smallest known isolated tooth of this species. The birth ring size (5–6.6 mm radial distance [RD]) overlaps with that of Archaeolamna kopingensis (5.4 mm RD) and the range of variation of Cretoxyrhina mantelli (6–11.6 mm RD) from the Smoky Hill Chalk, Niobrara Formation. The revised, reconstructed lower jaw dentition of the holotype of Cardabiodon ricki contains four anterior and 12 lateroposterior files. Total body length is estimated at 5.5 m based on 746 mm lower jaw bite circumference reconstructed from associated teeth of the holotype.

Copyright © 2015 M.G. Newbrey et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (for details please see http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Michael G. Newbrey, Mikael Siversson, Todd D. Cook, Allison M. Fotheringham, and Rebecca L. Sanchez "Vertebral Morphology, Dentition, Age, Growth, and Ecology of the Large Lamniform Shark Cardabiodon ricki," Acta Palaeontologica Polonica 60(4), 877-897, (11 October 2013). https://doi.org/10.4202/app.2012.0047
Received: 11 April 2012; Accepted: 1 October 2013; Published: 11 October 2013
KEYWORDS
Archaeolamna
Australia
Cenomanian
Chondrichthyes
Cretaceous
Lamniformes
Squalicorax
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