A fossil marine reptile, marked by the critters that gnawed its remains, may reveal how corpse eaters changed during the dinosaur era.
When modern whales die and fall to the ocean floor, their corpses sustain teeming ecosystems for decades. But before whales evolved, reptiles such as the dolphin-like ichthyosaurs ruled the oceans. Now it seems a 3-metre ichthyosaur from 157 million years ago supported a similar community.
"This is the first time anybody has described the ecological succession in the Mesozoic equivalent of a whale fall in detail," says Richard Twitchett of the Natural History Museum in London, who led the study.
Modern whale falls go through three stages. First, scavengers like fish pick the carcass clean of flesh. Then snails and bone-eating zombie worms feast on blood and fluid oozing from the remains. Last, when only the skeleton is left, microbes eat the bone lipids, animals like tube worms live off them, and the zombie worms eat on.
Death eaters
Twitchett and his colleagues examined tiny fossils on and inside an ichthyosaur's bones to find out what happened after it died. They found bite marks and grooves left by scavengers on the bones. They also found many molluscs similar to those from the second, slime-eater phase.
But there was no sign of that final stage. Instead, microbes in the fatty skeleton supported a different set of animals, including sea urchins and oysters.
In 2008, Andrzej Kaim of the Institute of Palaeobiology in Warsaw, Poland, and his colleagues found a "modern" final phase in a fossil from later in the dinosaur era (Acta Palaeontologica Polonica, doi.org/bmz82c). The community may have changed by then, says Twitchett.
We can't know that, says Steffen Kiel of the University of Göttingen in Germany, as the ichthyosaur died in shallow water, but modern whale falls are deeper.
Journal reference: Nature Communications, DOI: 10.1038/ncomms5789
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