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Re: Scales, hair, integumentary structure relationships?
Is there any evidence for reptile scales being homologous to hair?
Only on the deepest level -- as outgrowths of the epidermis.
The early Sarcopterygii and presumably early tetrapods had scales- "fish
scales", not homologous to reptile scales.
The tetrapods branched into many groups such as
temnospondyli, seymouriamorpha, and what went on to become
todays amphibians, reptiles, mammals.
The seymouria group apparently had scale structures, at least in
juveniles, can anyone infer if these resembled ancestral fish scales, or
if they more closely resembled the ancestral structure to repitllian
These are "fish" scales -- bone plates in the dermis. Some of today's
caecilians retain such scales, though they are very poorly ossified. Amniote
scales are thickenings of the epidermis.
When did tetrapods loose their fish scales, did temnospondylli have fish
Almost all halfway articulated specimens of temnospondyls and lepospondyls
preserve "fish" scales.
Considering feathers appear to be modified scales, and
sinosauropteryx had feathers that weren't much more than hairy fuzz,
They did branch, though.
is mammallian hair a modified scale, with scale like structures being
ancestral to amniotes?
Imaginable, but rat tails have hairs between the scales...
Pterosaur "hair" - modified scales I assume?
Nobody knows. (Though of course that's the most parsimonious option.)
If mammal hair and reptile scales arise from an ancestral structure before
the reptile/synapsid split...
then wouldn't Sinosauropteryx "hair" be homologous to mammallian hair the
same relative way that bat wings and bird wings are homologous?
If so, then yes.