Dinosaur Fossil Shows Exquisite Skin Detail
More imaginary feathers on a dinosaur have been discovered. A BBC News article shows a cartoon of a dinosaur with feathers on its arms. This is strange, because the paper it refers to makes no claim about feathers – only that certain structures had been interpreted as feathers by some.
The original paper by Theagarten Lingham-Soliar (U of KwaZulu-Natal, South Africa) described a Psittocosaur from China that is remarkable in one respect: it exhibits dinosaur skin in cross section with the finest detail ever found. Published in the Proceedings B of the Royal Society,1 the paper says that “Also, for the first time in a dinosaur two fibre layers parallel to the skin surface are preserved deep within the dermis at the base of the cross section.” Collagen at least 25 layers deep – maybe 40 layers deep – suggests that the skin of this species was tough and rigid, providing protection for internal organs. Tooth marks from a possible predator attack were also found. For these reasons, the author said this specimen “gives a remarkable, unprecedented understanding of the dinosaur skin.” It should, therefore, provide an ideal case for a feather hunt.
The BBC report made overt claims about feathers in addition to its cartoon: “The plant-eating Psittacosaurus had a thick layer of shark-like skin hidden under scales or feathers.” The caption said, “Some scientists believe a number of dinosaurs had feathers.” Another quote hedged a little: “Soft tissues such as skin are rarely preserved in the fossil record, leading to heated debate over what dinosaurs looked like, and whether they were covered in primitive feathers or scales.”
What did the original paper say about feathers? Not much. The only relevant statement was, “To date, all integumental structures described in dinosaurs, whether interpreted as ‘protofeathers’ or structural fibres, occur on the surface of the animal or on adjacent substrate.” A look at the references for such interpretations showed two for and two against. The most recent paper in the references was by Feduccia and Wang denying that so-called feathers are anything more than degraded collagen fibers. The only other comment about feathers in the paper was about the uniqueness of bird skin: “A generalization of the primary functional role of the dermis in the protection and/or support for the enclosed body mass may be extended to most vertebrates with the possible exception of birds, wherein the dermis plays a unique role with respect to feather attachments.” Nothing in the paper, therefore, supported the claim that the well-preserved skin of this Psittocosaur had feathers, despite the BBC’s depiction.
Update 01/10/2008: The author of the paper denies that these are feathers. Roger Highfield, reporting for the UK Telegraph, found out that the point of Theagarten Lingham-Soliar’s paper was to refute the notion that the collagen dermis layers contain proto-feathers. Here is what he told the Daily Telegraph:
Scientists must really now choose – belief in the nebulous idea of protofeathers or the reality of collagen, the dominant protein in vertebrates.
I am convinced from the nonsense spouted by many of the people who denounce collagen in favour of protofeathers that they have never actually seen collagen in its natural or decomposing state.”
Lingham-Soliar also denies that Sinosauropteryx, a turkey-size dinosaur unearthed in 1994, had feathers. He thinks, instead, that the impressions were remains of collagen that supported a dorsal frill running down the head and back.
Highfield ended his article, “Although the new work will not challenge the link between birds and dinosaurs it will lead to a fundamental rethink of why feathers evolved in the first place.”
1. Theagarten Lingham-Soliar, “A unique cross section through the skin of the dinosaur Psittacosaurus from China showing a complex fibre architecture,” Proceedings of the Royal Society B, ISSN: 0962-8452 (Paper) 1471-2954 (Online), Issue: FirstCite Early Online Publishing; DOI: 10.1098/rspb.2007.1342.
The evolutionary flights of fancy in the news media are irresponsible and detrimental to scientific objectivity. Here was another media flap by the BBC, trying to pull imaginary feathers out of leathery skin, because they so wish for dinosaurs to be the ancestors of birds (compare 06/13/2007). The Telegraph article was more fair, but still clung to the link between dinosaurs and birds as if that belief is too sacrosanct for evidence.
The reporters and scientists should have been questioning the 70 million years during which this specimen supposedly lay there, its skin exquisitely preserved down to the collagen fibers for all that time. The carcass of a cow, deer or bird will decay to the bone in months. The conditions under which such “extraordinary preservation” occurred, and a reappraisal of the dating, should be the first item of business.