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Darren Naish provided a thorough response (8/6/96; 12:13p) to my
questions about tuataras (plural!), for which I am grateful. I thought I
would mention one point, not to be picky, but just to show one of the
kinds of frustration one can experience in researching this material.
Actually, these statements are not necessarily contradictory.
>Tuatara lack an intromittent organ - unlike all other lepidosaurs - and
>19th century workers therefore thought them to be ineffectual lovers.
>Males are now known to distend their cloacas, in a similar fashion to
However, Jacques Gauthier wrote the following in his paper entitled "The
Diversification of the Amniotes," published by the Paleontological
Society as Short Courses in Paleontology Number 7: Major Features of
Vertebrate Evolution (1994), p. 133:
"_Sphenodon_ is mistakenly thought to lack a penis. It may not have the
elaborate hemipenial system of squamates, but its paired copulatory
organs are nevertheless composed of erectile tissue in the tail base."
Darren also asked:
>I think I'm right in that overlapping scales are one of the
>synapomorphies for lepidosaurs. The chemistry of these scales is unique.
Relative to scale composition, Gauthier said: "The skin in lepidosaurs
is equally distinctive. It is composed of superimposed layers of alpha
and phi keratin (Maderson, 1972), rather than having durable phi keratin
scales joined by pliable skin composed of softer alpha keratin as in
other reptiles. The skin is also shed regularly in its entirety, rather
than in an irregular and piecemeal fashion as in other amniotes (Gans,
1978). The mid-saggital crest, a projecting row of scales on the dorsal
midline of the neck, trunk and tail, also appears diagnostic of
lepidosaurs (Gauthier et al., 1988c)."
Note that there is no mention of the overlapping phenomenon that I was
especially curious about. Also, I wonder now about the Gila monster and
other lepidosaurs (would that include tuataras?) that don't have the
overlapping scales--it sound almost like they would have the second type
of skin Gauthier described, but apparently that is not the case.
Norman R. King tel: (812) 464-1794
Department of Geosciences fax: (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712 e-mail: firstname.lastname@example.org