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Dinos Shake Their Tail Feathers

August 30, 2012

Eva Gusnowski

The discovery of the feathered Archaeopteryx lithographica in 1861 was a great step forward for evolution, providing the once fabled link between birds and dinosaurs. But as more full fossils are being uncovered, Archaeopteryx might not be as unique as was once thought.

 

archaeopteryx



Archaeopteryx was a fickle friend when first discovered and was difficult to place. Although the feathers of this Jurassic creature resembled those of modern birds, the skeleton resembled those of small carnivorous dinosaurs.  And then, the lightbulbs went off and the link between birds and dinosaurs was made. This feathered creature was a rare find in the 1960s, however in more recent history (peanuts to the dinosaurs, though), many fossilized bird species from the Mesozoic era had been discovered.

Additionally, many non-avian theropods fossils have been discovered that demonstrate that these dinosaurs possessed a feathery coat, termed “proto-feathers”, as they are not feathers in the true sense of the word. In other words, though they are made of similar materials, they are not of the same structure as the feathers that Archaeopteryx or modern birds possess. However, a large number of dinosaur species that belong to a group of dinos called coelurosaurs possessed protofeathers and also likely possessed true feathers. This grouping of feathers within a small group of related species within a phylogenetic tree (a diagram that represents how closely related species are to one other, evolutionarily speaking) suggests that, at least to me, these species likely had an early common ancestor, and then just flew with it down the evolutionary tree (bad pun intended).

 

                                        Sciurumimus albersdoerferi, Rauhut et al., 2012

 

Even more recently, a new fossil, Sciurumimus albersdoerferi, unearthed in Asia was also discovered to have protofeathers. Insofar as fluffy, protofeathered dinosaurs go, this fossil is the oldest and most basal on the phylogenetic tree found so far. In fact, they found plumage everywhere along its body, implying that the beast was entirely covered in protofeathers. This fossil was, however, determined to likely be a juvenile, implying that at least the young of this species was fluffy, even if they may have lost the plumage later on during development. As many adult dinosaurs of these related species have scaly skin, this also implies that we shouldn’t necessarily take scaly skin as an absolute absence of feathers in these species, at least in the juveniles. Taking this a step further, this general rule can be applied to multiple dinosaur species. The analogy that the authors of the reporting paper make is one that I like…just because mammals are less hairy now doesn’t mean that our ancestors weren’t hairy, we just lost that trait over many generations. Similarly, many dinosaur species may have evolved from feathered or protofeathered species and lost this trait over time, while others retained it.

Rauhut et al.

Arrow = protofeather entering skin follicle, shown under a special light technique (Rauhut et al., 2012)



How many dinosaurs, then, were actually feathered? Only time will tell, because fossils can still talk. Now if only they could shake those tail-feathers. Actually, I take that back. Thanks Jurassic Park.

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