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Re: Young Allosaur feathers?

T. Michael Keesey <mightyodinn@yahoo.com> wrote:

1) Feathery integument first evolved in some tetanuran ancestor of the
aforementioned unnamed clade.
2) Feathery integument evolved even earlier, and _Carnotaurus_ is secondarily "feather"less.

I think (1) is more likely to be correct - though I'd be quite happy to be proved wrong (feathered eoraptors, for example). However the presence or absence of a feathery integument in a given taxon may also depend on other, non-phylogenetic factors. After all, _Sinosauropteryx_ has a feathery integument; but its kissing cousin _Compsognathus_ does not. In _Compsognathus_, the absence of feathers (especially in a specimen preserved in the same depositional environment as _Archaeopteryx_) is likely due to secondary loss.

Geographical, seasonal, ontogenetic and size-related factors almost certainly impacted upon whether a theropod exhibited the feathery body covering of its ancestors. For example, baby tyrannosaurs may have been clothed in down; but they shed their coats by the time they reached maturity. Ditto for allosaurs. Phylogenetic bracketing has its limitatons.


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