Dino dining on mammals: Canadian scientists part of rare discovery revealing diet of microraptors

An international team of scientists have discovered new evidence of a dinosaur dining on ancient mammals. 

The foot of a tiny mammal was inside the stomach of a microraptor — a small feathered dinosaur that lived during the Cretaceous some 100 million years ago in temperate forests in what is now China. 

It's the first time a piece of a mammal was discovered inside a microraptor. 

"Looking at interactions between animals, that's much easier to tell in the modern biology in living animals because we can actually go out and make those observations," said Caleb Brown, a curator of dinosaur systematics and evolution at the Royal Tyrrell Museum of Palaeontology in Drumheller, Alta. 

"Trying to make those inferences for fossils is more difficult because you don't necessarily know exactly which animal ate which other animal, unless you have exceptional cases like this."

This find alone will not change understanding of Cretaceous ecosystems and how they evolved, said Corwin Sullivan, a professor in the department of biological sciences at the University of Alberta, who was involved in the new discovery. 

But the discovery will contribute to the accumulation of paleontological knowledge and allow to "build up a very general picture of how food webs functioned, to some degree, in the geological past, how these various species were behaving and interacting," Sullivan said. 

"It's rare for a preserved fossil vertebrate to have any kind of gut contents, and certainly evidence of dinosaurs eating mammals is rare. 

"This adds to the evidence that microraptor in particular had what we describe as a generalist diet." 

As It Happens7:22Dinosaur's last meal preserved for more than 100 million years

Most food only lasts several days, weeks at most. But one microraptor fossil was found with the remains of its prey — a mammal's foot — still intact, more than 100 million years later. Hans Larsson, a McGill University palaeontologist and the study's senior author, tells As It Happens host Nil Köksal what this reveals about how these ancient bird-like creatures lived

Previously, microraptors were found with fish and lizards in their stomachs. The discovery provides hard evidence that carnivorous microraptors were generalist feeders. 

Generalists are really important in stabilizing ecosystems, said  Hans Larsson, the Canada Research Chair in vertebrate paleontology at McGill University in Montreal, who also participated in the research. 

"This discovery is telling us that microraptor was occupying this generalist feeding niche, whereas we know that other dinosaurs that were equally close to the origin of birds were doing a variety of different things ecologically," Sullivan said. 

"This adds to that picture of a rich diversity of dinosaurs closely related to birds inhabiting Cretaceous environments."

The researchers could not identify the mammal found in the microraptor, Larsson said, and 
the measurements of the foot don't match any known mammal that lived at that time. 

The animal probably superficially looked like a rodent and weighed about 15 grams, Larsson said. 

This knowledge, Brown said, is important because fossils like these allow scientists to better understand how ecosystems adapted to global change. 

"It's really only by looking at the past that we can see how ecosystems have changed and adapted in response to various perturbations, and from that we can really draw potential inferences for our current biodiversity crisis."