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RE: Tianyuraptor ostromi: yet another Liaoning dromaeosaurid



> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of B tH
> Sent: Wednesday, August 19, 2009 6:42 PM
> To: dinosaur@usc.edu
> Subject: Re: Tianyuraptor ostromi: yet another Liaoning dromaeosaurid
> 
> Really sounding like ancient Asia was a pretty dangerous neighborhood.
> 
> The experts say the atmosphere was too high in CO2 for us to 
> have survived back then - what about these dino's surviving 
> in today's atmosphere?  I'd think a high-metabolism animal 
> like a dromaeosaurid would be much more vulnerable to 
> atmospheric changes than a big lumbering sauropod.
> 
Several items here:

I don't think that the various Mesozoic CO2 levels would actually be
dangerous for a human; we wouldn't operate at peak efficiency, sure.
Depending on the model used, CO2 levels for the early Mesozoic
(Triassic-Jurassic) were up to 10x the pre-Industrial Modern of ~280 ppm);
by the end of the Cretaceous they seem to fall to 3-4x modern. I'm not
certain what level is lethal for humans, but I don't know if these reach it.
(Let's hope not: we will almost certainly reach 3x modern by the end of the
century).

More significant would be differences in oxygen levels. However, there is a
great debate over the appropriate models for reconstructing O2 levels. Under
the COPSE model, Triassic levels (after the recovery from the low at the
P/Tr boundary) start near present, rise to about 1.25x by the J/K boundary,
then spend the K between 1.25-1.5x present (with some variations as high as
2x). In stark contrast, the GEOCARBSULF calculations has all the Mesozoic
below present values, with a low in the Early J at about 0.5x present.

All that said, saurischians at least (sauropods and theropods alike)
seemingly had very sophisticated respiratory apparatus, so they might not
suffer so much for the changes.

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
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
http://www.geol.umd.edu/~jmerck/eltsite/
Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
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