Wednesday, April 24, 2013

Microraptor: Crow of the Cretaceous

Most of what we know about the diet of extinct animals comes from looking at their teeth, with obvious reasons. We can easily tell which animals were suited for slicing through flesh and which could easily grind vegetation, or which had teeth and jaws perfect for catching fish. There are a few instances, however, when we are lucky enough to actually find the preserved stomach contents of extinct animals. These findings, more than teeth or jaws, provide the most complete picture of what extinct animals were eating.

I've mentioned the diminuitive microraptorine Microraptor gui in a previous post. This little dromaeosaur has provided an enormous amount of information on not only the evolution of feathers and flight in non-avian dinosaurs, but it has revealed startling clues about its own habits. Like most other dromaeosaurs, M. gui was a predator, likely feeding on mammals, insects, and other small prey. In 2011, a specimen of M. gui was found with the fragments of bird bones in its stomach, indicating that it was an adept aerial hunter capable of taking out smaller, feathery prey on the wing (O'Connor et. al, 2011). This specimen revealed that Microraptor was, definitively, an arboreal hunter. However, just last week, another specimen of Microraptor revealed something even more surprising.

The new specimen of Microraptor. The preserved fish scales can be seen in the magnifying glass. Photograph by Scott Persons.
It turns out that the largest specimen of Microraptor, which also contains the remnants of its last meal, was preserved with fish scales in its stomach (Xing et. al, 2013). Did the specimen in question hunt the fish it was preserved with, or was it washed upon the shore of an ancient lake? These are questions we can't determine through fossils; however, Microraptor does not display any particular adaptations for fishing. The animal probably scavenged the fish, or managed to catch it in very shallow water. Either way, this changes our perception of the dromaeosaur in a very unexpected way. Instead of regarding Microraptor as a skilled arboreal hunter, which it most certainly was, it appears that the little glider was more of an opportunist than we imagined.

Microraptor eating a fish. Whether the specimen hunted the fish or was scavenging remains uncertain. Reconstruction by Emily Willoughby.
Between the discovery of the color of Microraptor, and clues about its generalist lifestyle, it seems as though Microraptor was the Cretaceous equivalent of a crow. Hopefully, more specimens are unearthed with stomach contents in tact. I wouldn't be surprised if we found stomach contents revealing something like this...

Microraptor gui feeding on a cycad. Reconstruction by Emily Willoughby.

O’Connor, Jingmai, Zhonghe Zhou, and Xing Xu. 2011. “Additional Specimen of Microraptor Provides Unique Evidence of Dinosaurs Preying on Birds.” Proceedings of the National Academy of Sciences (November 21). doi:10.1073/pnas.1117727108.

Xing, Lida, W. Scott Persons, Phil R. Bell, Xing Xu, Jianping Zhang, Tetsuto Miyashita, Fengping Wang, and Philip J. Currie. 2013. “Piscivory in the Feathered Dinosaur Microraptor.” Evolution: n/a–n/a. doi:10.1111/evo.12119.

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