Shake Your Tailfeathers, Cretaceous Style


When it comes to fancy courtship displays, birds rule the roost: their outlandish antics have been the subject of endless fascination, nature documentaries, and YouTube videos. The feathered creatures make moves that seem to be unparalleled in the natural world. (No, Michael Jackson concerts don’t count as the “natural world).

It is important to keep in mind, however, that modern birds are not the only feathered creatures to have ever walked—or, perhaps, danced—the earth. There is now abundant evidence that at least some dinosaurs sported feathers as well. (The theory birds are descended from dinosaurs and the debate surrounding that issue are beyond the scope of this post but certainly worth reading up on if that's all new to you). This revelation has opened up new realms of investigation involving signaling behavior and social cues related to the arrangement and coloration of dinosaur feathers. Unfortunately, data on integumentary details are exceedingly difficult to obtain from the fossil record—which is one reason it took us so long to figure out that many dinosaurs were feathered in the first place.

 

In a forthcoming issue of the journal Acta Palaeontologica Polonica, three paleontologists posit that fossilized oviraptors possessed structural features that are characteristic of those found in modern birds with ornamental tails (Persons 2012). For example, in the early oviraptor Similicaudipteryx, the last caudal vertebrae (the tip of the “tailbone”) are fused into a structure known as a “pygostyle," which was long thought to be a feature exclusive to modern birds. There is no evidence that Similicaudipteryx was a flying species, and Persons et al. suggest that the bone and muscle structures that can be discerned from the fossil remains are consistent with those seen in birds with tail displays that don't aid in flying but do functional as flashy ornaments, such as peacocks, turkeys, and birds of paradise (note that these birds are not completely flightless, the tails just don't contribute to optimal flight). Some species do indeed favor form over function, and apparently the trend may have started way back in the Mesozoic.

Pygostyle (Henderson State University)

Specifically, Persons et al. point to the presence of a series of numerous small vertebrae at the base of the tail and evidence of large, distally extended caudal muscles. These features would have given the tail a good deal of flexibility—perfect for “shaking its tail feathers” to attract mates. Similicaudipteryx’s good looks were not limited to its posterior: the dapper species sported a bony crest that also may have functioned in display behavior, either to attract mates or to intimidate competitors.

These assertions are, of course, subject to skepticism due to the limitations of the fossil record. This is part of science—publishing new perspectives or conclusions and allowing the scientific community to contribute further analyses and information--ultimately either supporting or discarding the idea. What is unquestionable, however, is that this paper signifies just how far paleontology has come in recent years. New finds and new technology have yielded broader an deeper information about the details of what dinosaurs actually looked like, how they moved, and how they might have interacted in their ancient world. As demonstrated by Persons et al., our increasing knowledge of dinosaur ornamentation and muscle structure means that areas of inquiry—behavior, social structure, mating systems, for example—that have long been of interested can finally be tackled scientifically. Worthy of a tail shake, no?
ResearchBlogging.org
Persons, S. W., Currie P. J., and Norrell, M. A. (2013). Oviraptorosaur tail forms and functions Acta Palaeontologica Polonica DOI: 10.4202/app.2012.0093

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