Fluctuations morphologiques et hétérochronies chez Toxaster (échinides, Crétacé inférieur)


fr Comptes Rendus Palevol 2 (6-7) - Pages 597-605

Published on 30 November 2003

This article is a part of the thematic issue Les chemins de l’Évolution : sur les pas de Steven Jay Gould

Morphological fluctuations and heterochronies of Toxaster (echinoid, Lower Cretaceous)

Several steps of the diversification of the spatangoid Toxaster are described with an analysis of six species distributed over the north-west Tethyan margin, and ranging from the Lower Valanginian to the Barremian. Morphological variation was investigated with the analysis of two parameters (angles), which allowed recognition of three modules on the test. Comparison of ontogenetic trajectories of two reference species (T. granosus kiliani and T. retusus) suggests a peramorphic heterochronic pattern. However, no peramorphocline can be attested when comparisons are extended to adults of the six species. Evolution among these species is partially driven by allometric changes in one module, indicating an important influence of size. On the temporal and spatial scale of the study, the evolution of Toxaster appears globally quite conservative.


Ontogeny, spatangoids, Toxaster, Lower Cretaceous, North-West Tethyan margin

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