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Re: Dino reputation 'is exaggerated'




Phil actually discusses the nature of the keratin sheath in the paper - He concludes that it's constructed of beta-keratin by using the Extant Phylogenetic Bracket (Witmer, 1995). Mammalian keratin is made of alpha kerotine, while reptiles and birds have the beta form. See excerpt below:


--> "The morphology of the fossil ungual claw cores of dromaeosaurs
combined with rare soft tissue preservation (Clark et al. 1999)
indicates that it would have been protected by a similar keratin
sheath. Extant Phylogenetic Bracketing (EPB: Witmer 1995) can
be used to reconstruct the structure and properties of the keratin
claws possessed by non-avian dinosaurs. Mammal claws are
composed of an a-keratin (helical), but bird and reptile claws are
composed of b-keratins (pleated-sheet) (e.g. Fraser & MacRae
1980). Given that dinosaurs fall within the EPB of birds and
crocodilians, it is likely that the claws of dinosaurs were composed
of b-keratin. Experiments to determine the Young modulus of
ostrich claw b-keratin indicated that they are mechanically aniso-
tropic, a property arising from the orientation of the keratin fibrils
(Bonser 2000)."

Also, the specifics on the robotic leg are in the paper too - They calculated the force for a 2m tall 40kg animal, and attacked both pig and crocodilian skin. They used both Velociraptor and Deinonychus as a model.

Its a good paper, here is the reference: Manning, PL., Payne, D., Pennicott, J., Barrett, PM., Ennos, RA. (2005). Dinonsaur killer claws or climbing crampons? Biology Letters of the Royal Society. Published online

Emma

----------------------
E Schachner, Earth Sciences
es4772@bristol.ac.uk