A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes : Squaliformes) based on dental characters

Citation
S. Adnet et H. Cappetta, A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes : Squaliformes) based on dental characters, LETHAIA, 34(3), 2001, pp. 234-248
Citations number
126
Categorie Soggetti
Earth Sciences
Journal title
LETHAIA
ISSN journal
00241164 → ACNP
Volume
34
Issue
3
Year of publication
2001
Pages
234 - 248
Database
ISI
SICI code
0024-1164(200109)34:3<234:APAPAO>2.0.ZU;2-6
Abstract
Squaliformes comprise the major proportion of modern deep-water sharks, yet their fossil history and phylogenetic relationships are still poorly under stood. New analyses have been undertaken, however, and new living and fossi l species have been discovered during the past 10 years. A cladistic analys is involving 29 dental characters has been made and most living and fossil genera are included. On the basis of their dental morphology, the monophyly of the Squaliformes can be supported if the fossil genus Protospinax is ex cluded. The traditional phylogenetic positions of most living genera, Proto squalus, Cretascymnus and Eoetinopterus, are confirmed despite the fact tha t the Oxynotidae, Etmopterinae, Palaeomicroides, Proetinopterus and Microet mopterus have some atypical phylogenetic relationships within the Squalifor mes. The addition of the palaeontological data in a phylogenetic tree inclu ding fossil and living Squaliformes demonstrates some gaps in the fossil re cord. Nevertheless, and as a consequence of that stratigraphy-phylogeny inf erence, two particular events can be pinpointed in the history of the Squal iformes: the first one occurs after the major Cenomanian-Turonian anoxic ev ent and the second one after the Cretaceous/Tertiary crisis. The first radi ation involves the majority of the living Squaliformes (Somniosinae, Centro phorinae, most of the Etmopterinae, Oxynotinae) in deep-sea waters, the sec ond, the more epipelagic sharks (most of the Dalatiidae), suggesting a seco ndary adaptation to more shallow environments.