I don’t know why a raven is like a writing desk, but I do know that Microraptor was like a cat. The feathery little dinosaur was cute and glossy, but those adorable features were offset by the carnivore’s excessive pointiness. Even though the non-avian dinosaur was about the size of a raven, and even had feathers with an iridescent corvid sheen, Microraptor still bore pointed teeth, grasping hand claws, and the classic deinonychosaur switchblade talons on each foot. All of this made Microraptor a cuddly-looking little cutter, much like a cat. And the dinosaur shared something else with felines – a fondness for fish.
Since the time the dinosaur was named in 2000, paleontologists have discovered multiple specimens of Microraptor in the 120 million year old lake deposits of China. Many of these are not only articulated, but fossilized to such a fine degree that the petrified remains of their feathers remain intact. This hi-def preservation also safeguarded tatters of Microraptor meals. One Microraptor individual, described two years ago, had feasted on an early bird shortly before perishing in a case of non-avian dinosaur eats avian dinosaur. But a Microraptor known as QM V1002 enjoyed a different last meal.
Fossilized in the position of QM V1002′s stomach, paleontologist Lida Xing and colleagues explain in a new Evolution paper, are the scraps of bony fish. A small mass of fin rays, vertebrae, and other piscine tidbits are tucked between the dinosaur’s ribs, some of which had been etched by digestive fluids when the Microraptor was still alive. The question is whether this Microraptor actually caught fish or just happened along some convenient snacks thrown up onto the lakeshore.
The Microraptor known as QM V1002 fed on fish, just as the one designated IVPP V17972A ingested an archaic bird. But even such intimate associations as food in the guts of predators does not tell us how those carnivores actually obtained that ingesta.
In their paper on the bird-eating Microraptor, Jingmai O’Connor and colleagues proposed that the quad-winged dinosaur actively caught avian prey, thus supporting an arboreal lifestyle for the feathery deinonychosaur. But the Microraptor could have just as easily happened upon a dead bird and snaffled up the free meal. (The ground-dwelling, fuzzy dinosaur Sinocalliopteryx may have done the same.) Without a time machine, there’s no way to tease apart the evidence into a clear case of hunting or scavenging. We only have the mashed-up aftermath.
Such is frustratingly the case with the fish-eating dinosaur, too. While Xing and collaborators mention that fish flesh has a relatively short spoilage time, perhaps arguing against scavenging, there’s no way to distinguish between the two alternatives on the basis of the available evidence. All we know for sure is that Microraptor sometimes ate fish, just as the dinosaur consumed birds and (based on yet another specimen) small mammals. Microraptor was a predatory generalist, Xing and coauthors conclude, probably capable of snatching small prey while also enjoying the occasional opportunity to horf down carrion.
Of course, technical papers must be conservative by nature. Saying that Microraptor hunted fish simply because one specimen was found with partially-digested fish flotsam inside, without considering other possible routes of ingestion, would be careless science. But dinosaurs are not just animals of technical journal arcana. Dinosaurs live where science and imagination meet, and, based on the spread of evidence, there is nothing illegitimate about picturing a Microraptor casting its wings over the water to create fish-friendly shade to attract swimming prey that could be then speared with a quick jab of a talon. Nor are visions of Microraptor gliding through Cretaceous forests to snatch early birds unreasonable or outlandish. These vignettes are prehistoric possibilities – what may have existed but remain just beyond the strict reach of direct scientific examination. The scattered data dots about the natural history of Microraptor may seem to be a sparse, limiting set of criteria, but, connected, they allow us to speculatively revive one of the most magnificent little carnivores of any era.
[Hat-tip to paleontologist Thomas Holtz, Jr. for pointing out the cat-deinonychosaur similarities that inspired this post's opening lines.
Top Image from the University of Texas at Austin.]
Xing, L., Persons, W., Bell, P., Xu, X., Zhang, J., Miyashita, T., Wang, F., Currie, P. 2013. Piscivory in the feathered dinosaur Microraptor. Evolution. doi:10.1111/evo.12119