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Re: Questions about dinosaur skin



>Some questions from a dermatologist (human, not veterinary) who is taking a
>dinosaur workshop at a local community college for fun: (1) is what is known
>with certainty about the skin of dinosaurs limited to information derived from
>fossilized skin impressions?

Primarily this, but also phylogenetic comparisons with other sauropsids.

>(2) do the variously-patterned tubercles and plates
>found in the skin impressions of dinosaurs differ significantly from those
>found
>in the now-living descendants of archosaurs?

Well, it does differ from the primary integumentary structure of surviving
members of the dinosaurian lineage, i.e., scales. ;-)  However, they do not
seem to be far off of bird or croc or turtle scales, but not quite like the
overlapping scales of lepidosaurs (tuataras and squamates).

>(3) are dinosaurian skin scales
>exclusively epidermal like those of birds and mammals, with no dermal scales as
>seen in fish? (human dermatologists mistakenly categorize genodermatoses with
>abnormal skin scaling as ichthyosis rather than reptilosis or herpetosis)

Very likely, although hard to test directly from impressions.

>(4) did epidermal skin scales develop in dinosaurs and other reptiles to
>prevent
>desiccation in a terrestrial environment?

This is the primary idea accepted by many paleontologists.

>(5) is the fact that epidermal scales
>allow infrared radiation from the sun to pass through the skin of significance
>for the maintenance of a constant dinosaurian body temperature?

Possibly, although more precisely it may have something to do with the
thermoregulation of the common ancestor of all sauropsids, and was
inherited by that ancestor's descendants (regardless of possible later
thermophysiological change).

>(6) did dinosaurs have multicellular glands analogous to human sebaceous and
>sweat
>glands?

Probably not.  Loss of glandular skin is one of the shared derived
characters of Sauropsida. (Glandular skin is present in fish and
amphibians, and is a primitive retention in mammals).

>(7) does anyone have definite knowledge of the color of dinosaur skin?

For dinosaurs in the "nonavian" sense, no.

>(8) did dinosaurs have chromatophores in the dermis which were regulated by
>hormones and the nervous system?

Big question.  Very difficult to test.

>(9) what are the chances that at some future time mummified dinosaur skin may
>be discovered which >might be rehydrated, processed and stained for
>examination under the microscope, such as has been
>done with human mummies?

I'd say slim-to-none, but I'd really like to be wrong about it.  (65
million years of preservation in the rock record does a lot to skin that a
couple of kiloyears in a purposely-constructed preservational environment
doesn't do...).

>These questions are being posed after personal study
>of "Dinosaurs The Text Book" by Spencer Lucas, a chapter on comparative
>dermatology in Rooks' Textbook of Dermatology, a computer search of the
>National
>Library of Medicine's Medline, and some articles on mummified human skin I
>saved
>from dermatology journals.  Bruce Howard - 70410.3262.@compuserv.com

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.