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Re: Tianyulang implications



The degree of body coverage is very important in assessing the function of the 
fibers/filaments/protofeathers. The illustration that's been widely circulated 
is misleading in showing only a mohawk-like frill along the backbone, and I'm 
afraid it may have misled some observers. Hai-Lu You told me in an e-mail that 
based on the fossil "at least the whole dorsal side and the ventral body were 
covered." Obviously more fossils would help resolve any doubts. 

It's going to take time for the press as well as paleontologists to assimilate 
the whole importance of this. Plus, of course, more fossils with well-preserved 
integument. 

At 1:58 PM -0400 3/19/09, GSP1954@aol.com wrote:
>Tianyulong provides the following information -
>
>Because the fibers are both dorsal and ventral to the body, and scales are 
>absent, a situation similar to Yixian birds, it is probable that most of the 
>body was covered. This is in contrast to the Yixian Psittcosaurus in which the 
>fibers are only dorsal to the tail, and scales are well preserved over most of 
>the rest of the body. Eventually additional small heterdontosaur fossils from 
>Yixian will address this item.  
>
>It is not possible for the fibers to represent internal collagen. They are 
>too long, extend much too far from the body even on the tail, and are oriented 
>in exactly the manner of external fur and feathers (sweeping outwards and a 
>little posterior rather than the more irregular, criss-cross pattern expected 
>of 
>collagen). This pattern is repeated on numerous Yixian theropod specimens as 
>well as birds. Nor has it been explained why small dinosaur skin was packed 
>with so much collagen -- they were not spring bodied ichthyosaurs after all. 
>The 
>collagen hypothesis is scientifically deceased unless heterodontosaurs or 
>small theropods with extensive scale coverings show up. 
>
>The absence of preserved protofeathers on Triassic and early Jurassic 
>theropods is meaningless because this is entirely negative evidence, and 
>scales have 
>not been found on them either. This is the same misleading nonargument for 
>naked dinosaurs that I dealt with in the 70s, 80s and 90s until the Yixian 
>fossils showed up.      
>
>That such a basal ornithischian and dinosaur had fibers is neither surprising 
>nor novel, it is eminently logical and goes aways back. I mentioned the 
>possibility that insulation was widespread in archosaurs and may be basal to 
>dinosaurs in the Dinosaurs Past and Present volume in 87, and Predatory 
>Dinosaurs of 
>the World in 88. Not sure whether I or others published the hypothesis 
>earlier. The widespread distribution of insulation is logical in that it is 
>highly 
>probable that dinosaurs were tachyenergetic endotherms. I have been 
>illustrating small ornithopods with archofur since the 80s to keep their 
>little bodies 
>warm. Some degree of tachyenergy may have been evolving fairly early in 
>Triassic 
>archosaurs, including basal crocodilians, so insulation may extend well back 
>into the clade. That the idea of general dinosaur fiber coverings goes back 
>decades is not being properly covered in the literature or press. 
>
>The widespread distribution of dense fiber coverings in a variety of small 
>dinosaurs is strong evidence of their having elevated metabolic rates. Very 
>probably was critical to the ability of small dinosaurs to dwell in cold polar 
>winters that excluded reptiles in the Mesozoic. 
>
>GSPaul  
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-- 
Jeff Hecht, science & technology writer
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