Despite the large amount of evidence that birds are the direct descendants of a group of theropod dinosaurs some researchers continue to protest the association, one of the most vocal opponents of the idea being Theagarten Lingham-Soliar. Working with Alan Feduccia and Xiaolin Wang (two other outspoken critics of the same topic), Lingham-Soliar published a paper last year proposing that the “protofeathers” on the fossil Sinosauropteryx were collagen fibers and not feathers at all. I didn’t buy the hypothesis (see this summary for an excellent take-down) and the paper seems to have been largely ignored (Feduccia and others have been flogging the ideas that many of the feathers found on dinosaurs coming out of China or collagen fibers for years), but now Lingham-Soliar is back with a new paper on the controversial “bristles” on another dinosaur, although the popular media has once again managed to confuse this issue.
In a report just out in the Telegraph called “Bald Truth About Dinosaur Feathers,” reporter Roger Highfield falls flat on his face when discussing Lingham-Soliar’s new paper and the implications the research has for bird evolution. The piece opens with this lovely summary;
Prof Theagarten Lingham-Soliar at the University of KwaZulu Natal, claims today to have “refuted” a suggestion that primitive bristle-like structures that adorn the tail of Psittacosaurus are prototype feathers, as claimed by those seeking evidence to back the widely accepted idea of avian origins.
*Smacks head against wall.* For those of you unfamiliar with the details of this issue, Psittacosaurus was a Cretaceous ornithischian dinosaur that is grouped in the Infraorder Ceratopsia, better known as the “horned dinosaurs.” Being that ornithischians are about as old as saurischian dinosaurs (the Order to which bird ancestors belong), one of the earliest known representatives being the 210 million-year-old Eocursor, Cretaceous ceratopsid dinosaurs are about as distant from the direct ancestors of birds as you can get and still be a dinosaur. Psittacosaurus has nothing at all to do with bird-origins, then, and I don’t know anyone who has marshaled the existence of “bristles” or “filamentous integumentary structures” as evidence for bird origins among ornithischians. Indeed, the phylogenetic distance between Psittacosaurus and feathered theropods has made the presence of integuments on the ceratopsid controversial, so I am curious as to how Highfield came up with such an assertion as was printed.
The comments of Lingham-Soliar in the article further muddy the waters;
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.
Pretty cranky words, surely, but from what I have read researchers have primarily highlighted the differences between “protofeathers” and the potential “bristles” of Psittacosaurus. In the paper “Bristle-like integumentary structures at the tail of the horned dinosaur Psittacosaurus” by Mayr, et al., the scientists describe the structures found on the Psittacosaurus fossil to be integumentary structures that are not homologous to the structurally different “protofeathers” found on theropods. Even if Lingham-Soliar is right about the bristles on Psittacosaurus being collagen, then, this does not immediately mean that each instance in which feathers have been preserved is just another case of preserved collagen. Such a statement would be doing exactly what Lingham-Soliar is accusing other researchers of doing, and as many of you know he certainly has an agenda to put forward when it comes to feathers vs. collagen.
So what about the new paper itself? I may disagree with Lingham-Soliar about his characterization of the issues presented in the popular press and his other interpretations, but that doesn’t mean that I should dismiss anything he produces out-of-hand. Surprisingly, the paper does not address specimen SMF R 4970 or the issue of “bristles” on Psittacosaurus directly, the main thrust of the paper being a comparison between the Psittacosaurus specimen MV53 from the Lower Cretaceous of Liaoning Province, China and the decaying skin of a great white shark (Carcharodon carcharias). While the paper describes the integumental structures of Psittacosaurus, the illustrations accompanying the paper are blurry and generally of a low quality; half the time I don’t even know what I’m supposed to be looking at. For those of you wondering (as I did initially) why a shark was chosen for comparison, Lingham-Soliar reports that the fiber arrangement in the specimen seemed similar to that seen in sharks. The structures that Lingham-Soliar observed, then, seem to show that Psittacosaurus had thick, tough skin, presumably to help protect it from weather and predators. (As a side note, Lingham-Soliar says that the skin of the nurse shark is exceptionally thick as a defense against predation, but there is an important caveat to this. The skin of nurse shark females is much thicker than that of males as male bite the females during copulation, so skin thicknesses differ between the sexes in nurse sharks and seem to be an adaptation to mating behavior rather than strictly predation.)
Perhaps I’m missing something, but the new paper doesn’t seem to say much of anything about the bristles found on specimen SMF R 4970, so Lingham-Soliar’s statements in the Telegraph are especially bold. Admittedly I am not well-versed in the science of collagen and what happens to it during the course of taphonomic processes, but I see no reason why paleontologists should suddenly accept that any integumentary structure is just preserved collagen from the skin of the animal; the structures found on Psittacosaurus are still debatable and this paper doesn’t do very much to resolve what they might be. Even the paper itself was not arranged or explained very well and the illustrations suffered from many of the same problems that plagued the Sinosauropteryx piece from last year, so hopefully a better description of the preservation of the soft tissues present in specimen MV53 will eventually be undertaken. I’m sure some creationists will jump on the popular reports as evidence that the dinosaur-bird relationship has crumbled, but given the content of the paper I’m not even sure it merited any popular media coverage at all.
[Hat-tip to Michael for bringing this to my attention.]
Lingham-Soliar, T. (2008) “A unique cross section through the skin of the dinosaur Psittacosaurus from China showing a complex fibre architecture.” Proceedings of the Royal Society B, Published Online Tuesday, January 08, 2008
Mayr, G., et al. (2002) “Bristle-like integumentary structures at the tail of the horned dinosaur Psittacosaurus.” Naturwissenschaften, Vol. (89), pp. 361-365
Osborn, H.F. (1923). “Two Lower Cretaceous Dinosaurs of Mongolia,” American Museum Novitates, no. 95.