Tuesday, May 27, 2014

We Eat Our Own

Rodolfo Noguera

All right this came out a little bit ago and I have been meaning to get around to it so here goes.

An Additional Baurasuchid from the Cretaceous of Brazil with Evidence of Interspecific Predation among Crocodyliformes

Abstract-A new Baurusuchidae (Crocodyliformes, Mesoeucrocodylia), Aplestosuchus sordidus, is described based on a nearly complete skeleton collected in deposits of the Adamantina Formation (Bauru Group, Late Cretaceous) of Brazil. The nesting of the new taxon within Baurusuchidae can be ensured based on several exclusive skull features of this clade, such as the quadrate depression, medial approximation of the prefrontals, rostral extension of palatines (not reaching the level of the rostral margin of suborbital fenestrae), cylindrical dorsal portion of palatine bar, ridge on the ectopterygoid-jugal articulation, and supraoccipital with restricted thin transversal exposure in the caudalmost part of the skull roof. A newly proposed phylogeny of Baurusuchidae encompasses A. sordidus and recently described forms, suggesting its sixter-taxon relationship to Baurusuchus albertoi, within Baurusuchinae. Additionally, the remains of a sphagesaurid crocodyliform were preserved in the abdominal cavity of the new baurusuchid. Direct fossil evidence of behavioral interaction among fossil crocodyliforms is rare and mostly restricted to bite marks resulting from predation, as well as possible conspecific male-to-male aggression. This is the first time that a direct and unmistaken evidence of predation between different taxa of this group is recorded as fossils. This discovery confirms that baurusuchids were top predators of their time, with sphagesaurids occupying a lower trophic position, possibly with a more generalist diet.

The paper also included a putative, best guess food chain for the strange xeric Late Cretaceous Brazilian, croc dominated ecosystem. One thing I would add though- if you are going to go out on a limb and draw a food chain for an extinct ecosystem you should take into account the facultative effects that the only large herbivores in the system, sauropods, would have provided. The carcasses, dung, rotten eggs, and detritus produced by sauropods likely stimulated the entire food chain, starting with insects. Insects fed small crocs, fish, mammals, which were consumed by larger crocs, baurasuchids and ultimatley abeliasaurids.

What this immediately reminded me of was a bit on the PBS documentary about monitor lizards called Lizard Kings. The segment in question highlighted the work of lizard ecologist Eric Pianca. His work site is the Red Sands region of the Great Victoria Desert in Australia. Here he has found an incredible diversity of 55 lizard species, including 6 species of monitor, coexisting. He believes fire plays a substantial role in allowing this coexistence. And when he checks his pit-traps and when he looks and sees what the lizards are eating- he sees a lot of lizards eating lizards.

Godoy PL, Montefeltro FC, Norell MA, Langer MC (2014) An Additional Baurusuchid from the Cretaceous of Brazil with Evidence of Interspecific Predation among Crocodyliformes. PLoS ONE 9(5): e97138. doi:10.1371/journal.pone.0097138

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