Featherless dinosaur surprises scientists, according to a report in Nature, vol. 440, p329, 16 March 2006. Palaeontologists have found an exquisitely preserved small dinosaur in Upper Jurassic limestone dated as 151 million years old. The creature is about 75 cm long and has been named Juravenator starki after the Jura mountains of Bavaria in Germany, where it was found, and after the Stark family who own the quarry site.
The tail region of the dinosaur has well preserved detailed imprints of the animal’s skin and the scientists who studied it were surprised that it had typical reptilian scales, not the filamentous proto-feathers found on some other dinosaurs of similar type and evolutionary age.
The Nature editor’s summary of the research article comments: “The new find is as well preserved as Archaeopteryx but, surprisingly, it shows absolutely no sign of feathery integument, suggesting that the evolution history of feathers in dinosaurs is a more complex tale than was thought.”
They also found some impressions of soft tissue fibres which they described: “The remaining soft tissue is represented by a series of fibres central to the haemal arches of the 10th to 14th caudals and parallel to the axis of the tail. These fibres probably represent tendons of the hypaxial musculature and ligaments of the tail, as interpreted for similar soft parts associated with the skeleton of Scipionyx, although they could also correspond to bundles of subcutaneous collagen fibres.”
Editorial Comment: We are not at all surprised this dinosaur showed no sign of having feathers. In fact no dinosaur has been found that has real feathers. Some have been found with filaments associated with their skin impression. The comment about collagen fibres reminds us of bird expert Alan Feduccia statement about the fibrous imprints associated with some dinosaur fossils. Feduccia said: “Collagen is a scleroprotein, the chief structural protein of the connective tissue layer of skin. Naturally, because of its low solubility in water and its organization as tough, inelastic fiber networks, we would expect it to be preserved occasionally from flayed skin during the fossilization process.” (See Dinosaur Feather or Fibres? Evidence News, 2 Nov 2005.)
What he means is that collagen is a tough stringy substance and would be preserved longer than the other tissue components that normally hold collagen fibres tightly together in the skin. Therefore, in partially decomposed skin the collagen fibres would splay out so they looked like filaments projecting out from the skin but they were never feathers. We suspect that the fossil described above was preserved too rapidly for its skin to partially decompose and allow the collagen fibres to splay out.
The new dinosaur’s name also reminds us that names like Jurassic do not have anything to do with millions of years. It was the name applied to all rocks that looked similar to the rocks in the Jura mountains, i.e. the name was meant to be a shorthand description of where the rocks were originally studied, and what they looked like, not how old they were. (Ref. fossilisation, preservation)
Evidence News 12 April 2006