What dinosaurs ate - The belly of the beast

A chance discover y from China suggests some dinosaurs lived in trees

WHAT dinosaurs ate is, of course, a question as interesting and illuminating as what ate dinosaurs. In the case of one particular dinosaur, Microraptor, the matter was addressed in a presentation to the annual meeting of the Society of Vertebrate Palaeontology by Jingmai O'Connor of the Institute of Vertebrate Palaeontology and Palaeoanthropology, in Beijing.

Microraptor (see photograph) is one of many small, feathered dinosaurs found in what is now China that were alive during the Cretaceous period more than 66m years ago. Being feathered, it and its kind were cousins to birds. The actual split between the two groups, though, had happened much earlier, during the Jurassic period (the first known bird is Archaeopteryx, from 150m years ago), and by the late Cretaceous there were many species of bird around. What Dr O'Connor and her colleagues have found is the remains of one of those birds, of an as-yet-unidentified species, in the stomach of a specimen of Microraptor.

That is interesting. Discovering direct evidence of what a fossil animal ate, rather than having to infer it from details such as the shape of its teeth, is always valuable. But the find's true significance is a small detail of the prey's anatomy: the third toe of its foot. The size of the prey's third toe is important because, among birds, long third toes are helpful for grasping branches and perching in trees. Indeed, the trait is so useful for arboreal life that it is used by many avian palaeontologists to decide whether newly excavated species of fossil birds lived in trees or on the ground. And the last meal of this particular specimen of Microraptor did, indeed, have a long third toe.

That elongated toe suggests to Dr O'Connor that Microraptor, too, was arboreal, and hints that its feathers may have helped it to move through an environment where hops, jumps and flaps between branches were a regular part of its daily activity. Whether the first birds evolved from arboreal or terrestrial ancestors is a matter of lively debate among palaeontologists. A fossil formed so long after birds emerged does not, in truth, shed much light on that debate. But it does suggest feathers may have helped promote life in the trees, even for creatures that could not actually fly.

Source of Information : [The.Economist] Volume 401 Number 8759 Nov 12th - Nov 18th 2011