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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 scales?

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 scales?

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.