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Scales and keratin



I have skimmed the "Journal of Materials Science Leeters" paper about
Pangolin scales that Dann Pigdon referred to.  SERIOUSLY outside my area of
expertise, so I'm not sure what to make of it.  There was a table of
proportions of various amino acids in pangolin scale, "keratin form hair"
and "keratin from feathers" (no it didn't say what species either the hair
or the feathers were from): pangolin scale didn't match either of the others
(had, I think, a lot more tyrosine, as well as other differences).  On the
basis of some sort of analysis the authors seem to have concluded that
pangolin scale contains both alpha and beta keratin.  Is that a sign they
have convergently evolved the sort of scale Sauropsids have?

Pangolins are weird.  Paleomammalogists seem unable to make up their minds
about what early Cenozoic taxa they are related to, but one molecular study
assigns them to a clade Pegasoferae, otherwise containing the
(morphologically dissimilar and generally scaleless) Perissodactyls,
Chiropterans and Carnivorans: it may or may not be a real clade (molecular
studies not yet having settled down to a stable consensus), but at least it
has a memorable name!

Allen Hazen
Philosophy Department
University of Melbourne