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RE: Triassic Guaibasaurus slept like a bird

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of Renato Santos
> While I don't discount that another reason to curl up while 
> sleeping is to keep all body parts accounted for (and it 
> doesn't preclude use for thermoregulation), I do dispute that 
> the temperature had as little daily variation in the region 
> during the Triassic as you say.
> The ocean current regime along South America's coast would 
> overall be the same as now with the cold Humboldt (or 
> whatever the predecessor was called) going north cooling and 
> drying the atmosphere.
> http://media.web.britannica.com/eb-media/46/136146-004-CD208F62.gif
> So, that's why we had (and have) a desert there and with 
> clear skies and little humidity, nights would be fairly 
> cooler than the day.
> Pangea's landmass tended to make these effects more extreme 
> as it would during the day work against the cooling effect 
> and work with it during the night. And this is  not taking 
> the seasonal variation in temperatures into account.
> While it's true that the area in question was situated on the 
> warm temperate to arid cline I'm not sure I would expect much 
> difference (perhaps more extreme climate) from my situation 
> living in a Mediterranean region: one still gets frost in 
> winter and the occasional iced over puddles.

While it is true the desert nights would be cold, and a proto-Humboldt would 
indeed cool the western margin of Pangaea, that
proto-Humboldt would be nowhere as cold as present.

The extreme cold of Antarctic waters (and Antarctica, and the Antarctic Bottom 
Water, which spills along the bottom of the sea well
into the northern hemisphere) is due largely to the presence of a 
circum-Antarctic current. There is thus an uniterrupted flow of
water at very high latitudes not deflected up into more equatorial waters, 
allowing for the development of the coldest, densest
waters too form.

Prior to the separation of Antarctica from its Gondwanan sister-continents, a 
circum-Antarctic current was impossible and thus the
polar waters and polar regions were considerably warmer than at present.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661               

Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA