We've previously brought you impressive images of crocodylians - that's the group of reptiles that includes alligators, crocodiles, and caimans - being eaten by river otters and by snakes. Now we bring you some intense croc-on-croc violence. We share because we love.
Yesterday, paleontologist Pedro L. Godoy and colleagues reported a new fossil found in the Adamantina Formation in Brazil. The geology dates to the Late Cretaceous, and what's particularly important about the find is that the skeleton of the new critter, a crocodylian ancestor called Aplestosuchus sordidus, is nearly complete. Aplestosuchus is a member of the Family Baurusuchidae.
They say behavior doesn't fossilize; only bones do. For that reason, its hard to know much about the social behavior of animals who lived so long ago. But sometimes we get lucky. Sometimes we can make inferences about behavior based on the arrangement of the fossils we find. That's why this particular discovery is so exciting. The researcher found evidence that Aplestosuchus probably hunted other crocodyliforms.
They can tell because they found a fossilized remnants of another crocodylian inside the stomach cavity of Aplestosuchus.
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.
Although no complete specimens of sphagesaurids are known, comparisons to other mesoeucrocodylians (Caipirasuchus paulistanus and Araripesuchus gomesi) suggest that the remains correspond to an animal of about 60 cm in length.
By contrast, Aplestosuchus was about a meter long.
In the photo above, Aplestosuchus's ribs are highlighted in green, its other bones in orange, and its last dinner is in yellow.
This discovery, combined with others from the Adamantina formation, helped the researchers infer the broader food web of the Late Cretaceous in the part of the world that we would come to know as Brazil. In the diagram below, Aplestosuchus is labeled at #9 and its sphagesaurid meal as #14. Crocodyliformes are in black, other animals in grey.
For details on the rest of the food web, click here.
Read the entire open access paper at PLoS ONE.
Today is Dinosaur Day among the io9 Recruits, so check out Space and Animation for more dino stories. Yeah, we know that crocodylians aren't dinosaurs, but Aplestosuchus lived alongside dinos - and as the above diagram clearly shows, were probably eaten by theropods.
Header image: Artistic reconstruction of Aplestosuchus sordidus preying on a sphagesaurid. Drawing by Rodolfo Nogueira.