RE: Killer Pterosaurs?

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Dinosaur World
>
> Hi everyone.
> I?m doing some advanced work for a video project and would like your
> opinions on the following.
>
> If I proposed a theory that Pterosaurs were a carrier of, and had immunity
> to, a disease that was fatal to dinosaurs, and this disease played a partial
> role in the extinction of dinosaurs in the Late Cretaceous.  Could you
> please give me your opinions as to the plausibility of such an idea? And if
> you find it implausible, could you please tell me why.

Depends on what you mean by "partial role." As anything but a sequel to the big 
event, utterly implausible. Not entirely outside the
realm of possibility (much like under quantum mechanics there is a non-zero 
chance that everyone with the last name "Smith" might
suddenly turn to gold next Tuesday), but utterly implausible.

A) The Biggie: The K/T extinction was primarily NOT the extinction of 
terrestrial vertebrates. They are the frosting on the cake.
The big deal was what happened lower in the food chain: both extinctions and 
short term mass reduction in biomass. And both on land
and in the oceans.

A-prime) Just want to mention that the physical evidence for other massive 
global transformations at this time (Maastrichtian
Regression, which despite comments on this list is STILL recognized as a global 
phenomenon, with some minor overprinting by local
tectonics; Deccan Traps volcanism; and big rocks falling out of the sky) 
remains in place. So even if this is a science fiction
story rather than a documentary, you've got to have your disease scenario set 
with the above going on as well.

B) Even in terms of terrestrial vertebrates, the die off was not "dinosaurs and 
pterosaurs vs. everything else." Instead, there was
a lot more selectivity to it.

C) As already mentioned, members of the dinosaurian clade Aves managed to 
survive. So those species have to be immune, or otherwise
survive the dinoplague.

D) Why pterosaurs as the carriers? Why not enantiornithine birds? Or 
multituberculates? Or, since these are some of the main vectors
of disease today, why not insects?

D-prime) At present the pterosaur data for the latest Maastrichtian is very 
sparse, but there isn't presently any support for global
distribution of any pterosaur species. (I.e., no Maastrichtian _Columba livia_ 
currently known). So one pterosaur species might
spread the hypothetical disease over a continent or two, but not globally.

E) Why should pterosaurs be immune, anyway? It seems to me that if you make 
them vulnerable, you have a scenario to take out
pterosaurs, too!

On *possible* role for disease: chances are that individuals surviving the 
immediate aftereffects of the K/T impact would not have
been in the best of health anyway, so it isn't unreasonable to think there 
might have been small pockets of non-avian dinosaurian
survivors who succumbed to diseases in the days/weeks/months after the big boom.

> I realize that fossilized evidence of disease is rare, and so there may not
> be much evidence for support or nonsupport of such a theory, but I was
> hoping you could give me your personal opinions on this.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796