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Heterodonty in the European Phytosaur Nicrosaurus kapffi and Its Implicatinons for the Taxonomic Utility and Functional Morphology of Phytosaur Dentitions

Axel Hungerbühler
Journal of Vertebrate Paleontology
Vol. 20, No. 1 (Apr. 17, 2000), pp. 31-48
Stable URL: http://www.jstor.org/stable/4524062
Page Count: 18
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Heterodonty in the European Phytosaur Nicrosaurus kapffi and Its Implicatinons for the Taxonomic Utility and Functional Morphology of Phytosaur Dentitions
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Abstract

The dentition of Nicrosaurus kapffi, a phytosaur from the Norian of central Europe, consists of three distinct dental sets in the upper jaw, and two in the mandible. Dental sets are defined by: (1) gradual, linear transformations of dental characters within an array that results in characteristic end members; and (2) the position of each array within the jaws. The tip-of-snout set in the upper jaw comprises mainly the large fang-like anteriormost teeth. In the premaxilla set, the teeth grade from a conical, unspecialized form anteriorly to high, D-shaped and bicarinate teeth posteriorly. In the maxilla set the teeth grade from stout, conical, unspecialized forms anteriorly to triangular forms with expanded flanges posteriorly. The tip-of-mandible and the dentary set correspond to the tip-of-snout, and to an elongated maxilla set, respectively, but were studied in less detail. The presence of tripartite and bipartite dentitions (three versus two dental sets in the upper jaw) is suggested as a criterion for defining the degree of heterodonty in phytosaurs. By taking into account positional variation, it is suggested that dental characters can be used to identify the relative position of some isolated teeth and can contribute valuable information to the diagnosis of a phytosaur taxon, although the application of the latter is still limited due to incomplete knowledge. The tooth morphology suggests that the more derived, tripartite phytosaur dentition is differentiated functionally into greatly enlarged anterior teeth probably used to kill smaller prey instantly by stabbing, strong posterior premaxillary teeth to seize and subdue large-sized prey, and trenchant posterior maxillary teeth to effectively dismember larger prey items.

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