[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Why did small dinos become extinct?

Most accounts of the K-T extinction state that no purely terrestrial animal larger than a cat survived (crocs and champsosaurs are / were semi-aquatic). Cat-/chicken-sized non-flying predatory dinos are known (most notably Compsognathus). Why did small non-flying predatory dinos not survive?

David Marjanovic suggests the whole terrestrial ecosystem was devastated too baldly to sustain viable populations of predatory dinos. But this is too simple:
* Mammals survived. Why could small small non-flying predatory dinos not survive in similar ecological niches?
* The greatest devastation of plants was in N America, less in other parts of the N hemisphere, and even less in the S hemisphere. One would expect small non-flying predatory dinos to survive in at least some of the less devastated areas.

He also bases his response solely on the impact hypothesis. I've seen suggestions that the N and S hemispheres had separate wind systems, as they do now, so most of the fallout from Chixculub ( well N of the tropics) would have affected only the N hemisphere, except for the CO2 emissions. In others words, I don't think Chixculub is a sufficient explanation for the K-T extinction.

If another factor (e.g. Deccan Traps) was responsible for most of the extinction in the S hemisphere, one would expect a different pattern of extinction. This would only make the extinction of small non-flying predatory dinos a more complex problem.

David Marjanovic wrote:
I'm rather disappointed at the lack of response to my original question - is there a decent explanation for the extinction of small non-flying predatory dinosaurs (including those which are regarded by some as secondarily flightless birds)? The "standard theory" of the K-T extinction is that a catastrophe killed off vegetation, the herbivores starved and so the carnivores starved. But one would expect that small non-flying predatory dinosaurs could have survived by preying on lizards, invertebrates, mammals, etc. which survived the K-T extinction.

This requires that large numbers of individuals of mammals etc. survived, enough to sustain viable populations of predators -- and that was apparently not the case (as expected from the impact hypothesis). Indeed, several clades of mammals and lizards died out altogether.

No virus found in this outgoing message.
Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.17.1/1181 - Release Date: 11/12/2007 17:05