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Re: Big aquatic vertebrates (WAS: Re: Pterosaur size)

Might be support for endothermy in ichthyosaurs and pliosaurs... also, there 
are thermodynamic implications for air respiration vs gills. I thimk.


----- Original Message ----
From: Andreas Johansson <andreasj@gmail.com>
To: david.marjanovic@gmx.at; dinosaur@usc.edu
Sent: Wednesday, December 13, 2006 11:05:54 AM
Subject: Big aquatic vertebrates (WAS: Re: Pterosaur size)

On 12/13/06, David Marjanovic <david.marjanovic@gmx.at> wrote:

> As clear as for terrestrial vertebrates, I'd say. You might like the fact 
> that the biggest ichthyosaur (and probably the biggest marine vertebrate 
> before *Basilosaurus*) was Triassic, though -- but then it is far from the 
> ancestry of the later ichthyosaurs.

This reminds me of something I've long found a bit odd - since the
Triassic or so, most of the really big aquatic vertebrates, both
predators and plankton-feeders, have been tetrapods. The whales win in
both categories (sperm whales and blue whales respectively), but even
discounting them the biggest non-tetrapods are beaten by various
marine reptiles, far as I know. (Leedsichthys and whale sharks are
smaller than that mega-ichthyosaur, and the biggest pliosaurs appears
to have out-sized Carcharodon megalodon, the biggest predatory fish I
know of.)

Land might seem an odd route to maritime gigantism, but it's
apparently the best one. The only explanation I've seen suggested is
that air-breathing is more effective than gill-breathing, even tho the
gill-breathers can breathe continuously.

Andreas Johansson

Why can't you be a non-conformist just like everybody else?