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Re: Why did small dinos become extinct?

john hunt writes:

If you accept the global de-vegetation theory it is possible to postulate a
fast extinction of all large animals (bigger than a cat), everything that
was not an insectivore, as there must have been a bug spike to go with the
fern spike.

Not sure how the crocs made it through though.

No doubt there was an initial glut of carcasses for crocs and small theropods to scavenge from. Once they were gone (either eaten or rotted away), the lower metabolism of crocs may have given them an advantage, since they could have gone longer between meals than a high-performance theropod.

Being able to swim (crocs) or fly (volant theropods) may have also been an advantage, as either mode of travel would have allowed animals to cross long distances in search of scarce food. Purely terrestrial animals (non-volant theropods) may not have been able to travel the necessary distances between food resources efficiently enough. If you use more energy finding food than the food itself provides, then you eventually starve.

Then there are questions of genetic bottlenecks. Some modern rodents can found an entire population based on a single pregnant female, with few inbreeding problems. Other species suffer far more from inbreeding, and require a much larger gene pool to remain viable. I suspect those species susceptible to inbreeding tend to fare poorly during mass extinction events, while those that can bounce back quickly despite genetic bottlenecks tend to thrive. In the case of theropods, perhaps only some of the volant varieties were able to cross large enough distances between isolated pockets of survival to maintain a necessary level of genetic diversity.


Dann Pigdon
GIS / Archaeologist              geo cities.com/dannsdinosaurs
Melbourne, Australia             heretichides.soffiles.com