sábado, 25 de setembro de 2010

New fossil triakid sharks from the Eocene of Prémontré, France and comments on fossil record of the family

Sylvain Adnet and Henri Cappetta
Acta Palaeontologica Polonica 53 (3), 2008: 433-448
During the last two decades, an abundant selachian assemblage has been collected from the late Ypresian (NP12)
fossiliferous sands of Prémontré (Aisne, northern France) but has received little attention. Sharks of the family Triakidae (Carcharhiniformes) are particularly well represented and all are described and figured herein. Among them, two new species of the genus Galeorhinus are described: G. duchaussoisi sp. nov. and G. louisi sp. nov.; these are compared to the common Paleogene G. ypresiensis which is refigured. Another triakid taxon, the genus Gomphogaleus gen. nov., is described. Most of the triakids have been recorded elsewhere in the North Atlantic region, suggesting a wider distribution than expected for these small sharks during the Paleogene. The present paper updates the list of selachians from Prémontré, bringing the number of taxa from 19 to 33 (including 22 sharks and 11 batoids) and improving our knowledge of the ancient North Atlantic Ypresian selachian fauna. Despite this vastly improved record, it is clear that fossil data are still very incomplete and insufficient for calibrating phylogenetic hypotheses of living forms. Review of the Prémontré fauna shows that the Triakidae were much more diverse and broadly distributed than at present, suggesting that the limited distribution and low diversity of living forms is probably a recent phenomenon.

Key words: Chondrichthyes, Triakidae, Galeorhinus, Gomphogaleus, Eocene, France
Sylvain Adnet [sil20adnet@yahoo.fr], Departamento de Geocięncias. Universitade de Evora, Largo dos Colegias 2, 7000 Evora. Portugal; Henri Cappetta [henri.cappetta@univ−montp2.fr], Département Paléontologie, Phylogénie and Paléobiologie, UMR 5554 “Institut des Sciences de l'Evolution”, Université de Montpellier II – Sciences et Techniques du Languedoc, Cc 064, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.

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