The first mammals were small and elusive, but that didn鈥檛 stop them chowing down on dinosaur meat. A bone fragment from a giant dinosaur has bite marks that could only have been made by small mammals, which probably scavenged the carcass.
鈥淭his is the earliest direct evidence for mammalian feeding behaviour,鈥� says Felix Augustin at the Eberhard Karls University of T眉bingen in Germany.
The bone fragment came from the long neck of a sauropod dinosaur, which lived in what is now China in the late Jurassic around 160 million years ago. By this time dinosaurs had dominated ecosystems for tens of millions of years. Mammals lived alongside them, but most were small and unobtrusive while the dinosaurs ruled.
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Augustin and his colleagues had previously found bite marks on dinosaur bones from elsewhere, so they took a close look at the Chinese specimen. 鈥淚 recognised small gnawing-like feeding traces,鈥� says Augustin.
To find out what made the traces, the team compared them to bite marks made by different kinds of animal and by other processes like trampling. Crucially, the teeth marks were often found in pairs. That matches the paired incisors mammals have at the front of their mouths. Meat-eating dinosaurs and other dinosaur-era animals don鈥檛 have paired incisors.
No mammal remains were found with the sauropod bone, but a nearby bone bed held teeth from five Jurassic mammals. Only one species, Sineleutherus uyguricus, had an incisor preserved. In size, this matched the bite marks, says Augustin. However, he says it isn鈥檛 possible to say with confidence that S. uyguricus, and not another mammal, made the marks.
The mammals must have been scavenging, says Augustin, as it isn鈥檛 possible that such tiny mammals could have taken down a huge sauropod dinosaur.
Most of our knowledge of early mammal diet comes from their teeth, says Augustin. This evidence points to an insect-based diet, like many small mammals today. The bite marks suggest that early mammals may have eaten quite a varied diet, with regular insect meals supplemented by scavenging meat from carcasses.
The Science of Nature
