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Re: Antarctic Elasmosaur




There is no reason for them to have been endotherms, people don't seem to understand that aquatic ectotherms are homeothermic, because of the relatively constant temperature of the water around them, therefore, there is no reason to heat yourself above the water temperature, compare teleosts and ceteceans, there is no great difference in activity levels between them. Ceteceans are endotherms plesiomorphically because of their mammalian heritage, and to lose that would be impracticable due to adaptations of tissues etc. to higher temperatures. Elasmosaurs are descended from quite basal diapsids, and their terrestrial ancestors were certainly ectotherms, therefore, there is no reason for them to have wasted huge amounts of energy to no advantage in becoming endothermic. The main advantage of endothermy in terrestrial organisms seems to have been homeothermy, rather than higher temperatures per se.


Patrick

From: Jura <archosaur@reptilis.net>
Reply-To: archosaur@reptilis.net
To: larryf@capital.net
CC: dinosaur@usc.edu
Subject: Re: Antarctic Elasmosaur
Date: Wed, 27 Feb 2002 23:28:11 -0700

>
> -----Original Message-----
> From: Jaime A. Headden <qilongia@yahoo.com>
> To: dinosaur@usc.edu <dinosaur@usc.edu>
> Date: Monday, February 25, 2002 10:19 PM
> Subject: Antarctic Elasmosaur
>
>
> >Not dinos, but of some particular interest tro many list members, as well
> >as of ecological interest:
> >
> >Fostowicz-Frelik, £. and Ga?dzicki, A. 2001. Anatomy and histology of
> >plesiosaur bones from the Late Cretaceous of Seymour Island, Antarctic
> >Peninsula. In: A. Ga?dzicki (ed.), Palaeontological Results of the Polish
> >Antarctic Expeditions. Part III. _Palaeontologia Polonica_ 60: 7?32.
> >
> >Abstract:
> >
> >"Remains of elasmosaurid plesiosaur have been collected from the lower
> >part of the Late Cretaceous López de Bertodano Formation on Seymour
> >Island, Antarctica. This well preserved bone material includes pectoral,
> >dorsal, and caudal vertebral centra, femur, tibia, and fragments of the
> >humerus, scapula, and ischia, that most probably belong to the one
> >specimen. The microstructure of the bone tissue shows rather dense
> >structure with Haversian remodelling well underway and the areas of
> >intensive growth, suggesting subadult stage of ontogeny. The dense
> >pachyostotic character of the rib and girdle tissue, together with a
> >relative small size of the bones (approximated length of the animal about
> >two meters) may indicate that described material belongs to the not fully
> >grown elasmosaur, which may have lived in shallow water environment. The
> >studied remains share some similarities with those of Mauisaurus from the
> >Maastrichtian of New Zealand ? in the articular surface of the vertebral
> >centra and the shape of the tibia."
>
>
> One wonders then, (well,...I wonder then), if a case couldn`t be made for
> elasmosaurs being somewhat warm-blooded to be living in a Polar region?


+++++++++++++++++++++++++++

Depends on one's definition of warm-blooded.

If you mean they might have been endothermic gigantotherms (a la _D.coriacea_), I could see that.

If, on the other hand, you mean automatic endotherms (sensu Bakker), then I doubt it.

Jura


Ectoparasite: external parasites. Some common ectoparasites include: ticks, mites & personal injury attorneys.


The Reptipage
http://reptilis.net




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