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ICHTHYOSAUR PIGMENT



Do we really know what colour ichthyosaurs were? Dan Bensen 
wrote...

>  In the book Dinosaurs and
> Prehistoric Animals (primarily by Dougal Dixon) it says, "The remains
> of pigment cells have also been preserved and the analysis of these
> suggests that the smooth, thick skin of Ichthyosaurus was a dark
> reddish-brown color in life."  What ever became of that theory?  Is it
> still valid?

Whitear (1956) is the one reference everyone alludes to when 
discussing fossil pigment in ichthyosaurs (it is paper from _Ann. Mag. 
Nat. Hist._). Whitear reported microscopic structures in 
_Ichthyosaurus_ soft tissues that she interpreted as skin cells, and cells 
with dark brown melanocytes. Obviously I have discussed this quite a 
bit with David Martill, my supervisor and an authority on soft tissue 
preservation in marine reptiles - judging by his published abstracts he 
has formerly accepted this interpretation ('Some ichthyosaurs were 
brown (Whitear 1956)' (Martill 1997)) but I can't recall what his take 
is on it now. Many structures previously identified as 'skin cells' have 
recently been reinterpreted as non-organic, so Whitear's identifications 
need to be scrutinised.. also, if a fossil cell is brown, is that really an 
accurate representation of pigmentation during life? Also, I am reliably 
informed that Whitear's specimens are not of high quality (though this 
might be due to recent degradation (L. Steel pers. comm.)).

I think this has been covered on the list before (check the archives).

On a related matter, it is probable that preserved ichthyosaur soft tissue 
 outlines are not ALL autolithified bacterial mats: Keller (1992 I think, 
a _Kaupia_ paper) presented an alternative model. Those who work on 
this area seem to agree that neither model explains ALL of the cases. 

"Your little insurrection is at an end, your highness"


DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
Burnaby Building
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Portsmouth UK                          tel: 01703 446718
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http://www.naish-zoology.com]