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"hairs" in ornithodirans
Regarding the new heterodontosaurid paper, I thought some things...
(sorry if some are repeated)
-I have seen restorations of the heterodontosaur with "hairs" on the
dorsal midline... Is not this too innecessarily minimalistic? I mean,
as far as I was able to observe, in both "hairy" pterosaurs and
dinosaurs, you only recover "hairs" from the margins of the fossils,
not from, for example, the part of the skin which would cover all the
bones we see (integument would possibly be removed when looking to
expose the bones). "Hairs" only on the dorsal midline may mean "hairs"
in the dorsal surface.
-The authors of the "hairy" heterodontosaurid paper also seem too
cautious about homology of the "hairs" with protofeaters and pterosaur
"hair". One may, based on current evidence, agree with this relative
to "secondary homology": there are scaly dinosaur skin patches that
may suggest the "hairs" appeared independently in some Ornithischia,
Coelurosauria and Pterosauria (but not necessarily, as the preserved
scale patches do not cover the entire organism). But it can be said
they are primarily homologous at least given their filiform shape. The
burden of proof to dismiss primary homology (and secondary) would lie
in those who say these "hairs" are not homologous to other
ornithodiran hair, protofeathers and feathers.