Perspectives Paleontology:
Warm-Blooded "Sea Dragons"?
Ryosuke Motani
When dinosaurs roamed the land in the Mesozoic (251 to 65 million years ago), the top predators in the ocean were reptiles (1, 2). Three lineages of Mesozoic marine reptiles (plesiosaurs, ichthyosaurs, and mosasaurs) were especially successful (2) (see the first figure). They were similar to current marine mammals in many respects. They fed on fish, cephalopods, bivalves, and other air-breathing vertebrates (1). Ichthyosaurs evolved dolphin-like body plans. Plesiosaurs became underwater fliers, vaguely resembling sea lions (2, 3). It now appears that similarities to today's marine mammals extended further: On page 1379 of this issue, Bernard et al. (4) report that some ancient reptiles may have been able to sustain a constant body temperature (i.e., homeothermy).
Department of Geology, University of California, Davis, CA 95616, USA.
Source: www.sciencemag.org. Science 11 June 2010:
Vol. 328. no. 5984, pp. 1361 - 1362
DOI: 10.1126/science.1191409
Unfortunately I can’t publish the rest of the article as this is the only free bit. I have however read it and it is interesting in that it would mean such creatures could survive in colder waters.
In fact Heuvelmans was already aware of the situation in In The Wake of the Sea-serpents: The pattern of bone growth in Mesozoic marine reptiles indicated that they had the mammal-like lifestyle and some degree of Homeothermy. And sae creature that dives to great depths has simply got to be able to tolerate temperatures down to freezing.
ReplyDeleteHe mentions this in his chapter reviewing Oudemans' Megophias in the passage beginnng "Let's play the devil's advocate..."
Ultimately he says that a Plesiosaurian identity for the Longnecked type was not likely because the necks of Plesiosaurs were inflexible, citing a pre-WWI source. This is a matter that is still disputed and no consensus of opinion has been reached; but it is a fair statement to say that flexibilty of the neck varied in different types of Plesiosaurs.
There is also still controversy and no general consensus of opinion about how Plesiosaurs swam, or how fast they could swim.
A PS I have the full article on a pdf file if anyone would like it to read in full. Leave a comment and I will sort something out via email.
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