“We now know what the plumage looked like on the tail, and that from the mid-femur down, it had bare skin,” says Aaron van der Reest. This is the first report of such preserved skin forming a web from the femoral shaft to the abdomen, never before seen in non-avian dinosaurs. “Ostriches use bare skin to thermoregulate. Because the plumage on this specimen is virtually identical to that of an ostrich, we can infer that Ornithomimus was likely doing the same thing, using feathered regions on their body to maintain body temperature. It would’ve looked a lot like an ostrich.” In fact, this group of animals–referred to as ornithomimids–is commonly referred to as “ostrich mimics.”
The find is said to strengthen the link between dinosaurs and birds.
“This specimen also tightens the linkages between dinosaurs and birds, in particular with respect to theropods,” says Alex Wolfe, second author on the paper. “There are so many components of the morphology of this fossil as well as the chemistry of the feathers that are essentially indistinguishable from modern birds.” More.
If so, not much evolution in feather chemistry happened in all that time.
Should we add the feathers to our giant stasis chart?
See also: Stasis: Life goes on but evolution does not happen
Here’s the abstract:
A recently discovered articulated partial skeleton of Ornithomimus from the Upper Cretaceous Dinosaur Park Formation of Alberta, Canada is remarkable in the extent and quality of preservation of integumentary structures including feathers. It is the first ornithomimid to preserve a tail bearing extensive plumaceous feathers that are slightly more elongate in comparison to those present on the remainder of the body. However, the underside of the tail and the hind limb distal to the middle of the femur appear devoid of plumage. Overall, the plumage pattern in Ornithomimus is similar to that of Struthio camelus (ostrich) and other large palaeognaths, indicating a probable function in thermoregulation. The specimen also preserves the body outline around the legs, including a skin contour anterior to the femur, analogous to skin webs in extant birds. Whereas the knee web of birds bridges the knee to the abdomen, in Ornithomimus it spans from the mid-femoral shaft to the abdomen, and is herein referred to as an anterior femoral web. This is the first report of such soft tissue structures in non-avian theropods. It may indicate that the resting position of the femur was positioned more anteroventrally in ornithomimids than in most theropods, and in that sense may have been transitional to the situation in modern birds. (paywall) – Aaron J. van der Reest, Alexander P. Wolfe, Philip J. Currie. A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation, Alberta, Canada. Cretaceous Research, 2016; 58: 108 DOI: 10.1016/j.cretres.2015.10.004
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