Re: Re: extinctions

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

>James M. Norton, Ph.D. wrote:
>
>>Did a relatively sudden extinction event act on the adult animals
>>(the K-strategy) with all their different phenotypes, geographical
>>ranges, diets, sizes, habitats, etc., or did it act on their eggs
>>(the r-strategy), arguably the most vulnerable point in their life
>>cycle and the one point at which all dinosaurs would be most alike?
>
>Has it been determined beyond doubt that all dinosaur reproduction
>was based on egg laying? I thought there was some consideration
>given to the possibility that some had gone the way of live births.

Eggs and embryos have been found of most (but not all) representative
lineages within Dinosauria.  I know there is some discussion (which,
frankly, is a bit outside my field, so I'm not the best judge of the
research) suggesting that once highly prismatic eggshells (in all
dinos, including birds) was evolved, it was developmentally
constrained from developing an ovoviperous habit.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"There are some who call me...  Tim."