Re: Scales, hair, integumentary structure relationships?

[David Marjanovic <david.marjanovic@gmx.at>]

> 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.

Exactly.

> 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.