Paleodiversidad de crocodilomorfos en el XVI Annual Meeting de la EAVP

En el primer simposio europeo acerca de la evolución de los crocodilomorfos, celebrado en el XVI encuentro anual de la EAVP, A. de Celis presentó una comunicación oral del trabajo titulado “Revisiting the biodiversity curve of modern crocodiles (Crocodyliformes, Eusuchia)”. En este trabajo, realizado en colaboración con I. Narváez y F. Ortega del Grupo de Biología Evolutiva de la UNED, se presentaron nuevas curvas de paleodiversidad estimadas a partir del registro fósil de los cocodrilos eusuquios. Estos resultados se mostraron también divididos según continentes y según grandes linajes de Crocodylia (Alligatoroidea, Crocodyloidea y Gavialoidea), permitiendo por tanto entender cómo ha variado la diversidad de los cocodrilos eusuquios en términos espaciales, temporales y filogenéticos. Aquí el resumen:

The fossil record of modern crocodiles (Eusuchia) shows that, although their diversity is currently restricted to 23 recognized species circumscribed in three major lineages, in the past they were more abundant and had a wider distribution. Historically, many fragmentary fossils with limited diagnostic characters have been assigned to certain species exclusively on the basis of a shared spatiotemporal distribution. The large amount of these improperly justified taxonomic assignments should be taken into account in order to reconstruct the paleodiversity of any clade, as these occurrences could introduce another bias.

Regarding this issue, an exhaustive review of more than one thousand eusuchian body fossil occurrences at specific level has been carried out in order to build a new dataset, excluding dubious fossil occurrences. Following previous works, these occurrences were sorted into time-bins of about 9 million years and shareholder quorum subsampling (SQS) was applied to the dataset, obtaining a subsampled biodiversity curve comprising the entire timespan of Eusuchia. The resulting curve shows two great increases in eusuchian biodiversity, the first one during the Paleocene and the second one during the Middle-Late Miocene. These results are quite consistent with proposals already known. However, in contrast with previous works, our results suggest that the Middle-Late Miocene biodiverstity peak was bigger than that of the Paleocene. The Middle-Late Miocene biodiversity peak is related to the great expansion of alligatoroids in South America, with minor contributions of the gavialoid expansion in South America alongside the crocodyloid expansion in Africa and Australasia.

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