120-million-year-old dinosaur fossil hid a surprising meal in its stomach

A cat-sized dinosaur’s surprising lunch has been discovered in a 120-million-year-old Microraptor fossil. Although the fossil was first described in 2000it hid an intriguing and historic secret: A reanalysis of the fossil found the bones of a mammal’s feet inside the raptor’s ribcage—the first evidence of a dino eating a mammal.

the find, described in the Journal of Vertebrate Paleontology on Tuesdayis based on the previous research of the Microraptor zhaoianus fossil, discovered in the Jiufotang Formation in western China. This fossil is missing the middle part of its body, but the ribcage is visible, and inside, the bones of a small right foot, less than half an inch in size, were perfectly preserved.

Microraptors were three-toed carnivorous dinosaurs that occupied the trees of the ancient Earth and are among the smallest dinosaurs discovered. Fossils of different species of microraptors show evidence of long feathers on each limb, which they may have used for gliding.

As you might expect, being eaten doesn’t usually result in very well-preserved fossil remains. All that biting and chewing, plus digestion, usually leaves little trace of a meal. However, scientists have a pretty good idea of ​​the diet of microraptors thanks to fossils with undigested remains in their stomachs.

A bird, a fish and a squamate – the class of animals that includes lizards and snakes – have previously been found, but the new find helps paint a more complete picture of what went down the esophagus during a prehistoric tasting.

“It’s so rare to find examples of food inside dinosaurs, so every example is really important because it gives direct evidence of what they ate,” said David Hone, a paleontologist at Queen Mary University of London and first author of the new study

Although scientists can tell that a foot ended up in the microraptor’s stomach, they aren’t sure which species it belonged to. The thin fingers are similar to the tiny, extinct, possum-like mammals known as Sinodelphys or the closest thing to a mouse Eomaia. However, the digits are not long enough to be either species.

Another open question is whether Microraptor preyed on the mammal or whether it just removed its foot. It’s impossible to tell with this fossil, but some scientists have suggested that the microraptor’s feathery limbs may have allowed the species to glide from branches and onto the ground to prey on terrestrial species. The size of the mammal’s foot suggests that the creature would have been in the size range expected for microraptor prey.

The surprising fossil builds on previous evidence that these smaller three-toed dinosaurs made do with whatever was around; they may even have eaten plants at times.