Les premiers vertébrés et les premières étapes de l’évolution du crâne

Philippe JANVIER

fr Comptes Rendus Palevol 8 (2-3) - Pages 209-219

Published on 30 April 2009

This article is a part of the thematic issue Evolutionary history of Life

The earliest vertebrates and the first steps of the evolution of the skull

Vertebrates are one of the few metazoan taxa, which display a well-corroborated phylogenetic pattern, a good and anatomically informative fossil record, and a relatively slow ontogenetic development. They are thus a favourite taxon for illustrating evolution as a historical process, although the stem of the vertebrate tree remains poorly documented by fossils, except for some Early Cambrian forms. Therefore, the characterization of the vertebrates now rests essentially on a small number of developmental characters, mostly involved in the rise of the skull, and whose precursors may occur in other chordates. The tree of the crown-group vertebrates also shows some major morphological gaps due to early extinctions, but a number of Palaeozoic stem gnathostome taxa helps in documenting the agnathan-gnathostome evolutionary transition. However, stem cyclostomes remain elusive.


Vertebrates, Chordates, Phylogeny, Fossils, Morphological gaps, Evolutionary transitions

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