mercoledì 28 novembre 2007

Matrioske permiane

Se l'articolo di prima era una bufala, questo è vero!

Jürgen Kriwet, Florian Witzmann, Stefanie Klug, Ulrich H.J. Heidtke.
First direct evidence of a vertebrate three-level trophic chain in the fossil record. Proceedings of the Royal Society B 275 (January 22, 2008): 181-186

Abstract: We describe the first known occurrence of a Permian shark specimen preserving two temnospondyl amphibians in its digestive tract as well as the remains of an acanthodian fish, which was ingested by one of the temnospondyls. This exceptional find provides for the first time direct evidence of a vertebrate three-level food chain in the fossil record with the simultaneous preservation of three trophic levels. Our analysis shows that small-sized Lower Permian xenacanthid sharks of the genus Triodus preyed on larval piscivorous amphibians. The recorded trophic interaction can be explained by the adaptation of certain xenacanthids to fully
freshwater environments and the fact that in these same environments, large temnospondyls occupied the niche of modern crocodiles. This unique faunal association has not been documented after the Permian and Triassic. Therefore, this Palaeozoic three-level food chain provides strong and independent support for changes in aquatic trophic chain structures through time.

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