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Re: TUATARAS



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. 

Darren said:
 
>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 
>most birds. 

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. 
>Right?

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.


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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:  nking.ucs@smtp.usi.edu