Natural Science Forum / Biology / Paleontology / March 2007

You really need to fix your titles. This is the second ho-hum,
no-brainer title for what is really a very interesting result. You also
have to provide at least a short quote or abstract for the story.

So what this is all really about is using fossils to estimate the genome
sizes of extinct species. It's been done before with plants, using
approximately the same technique. It's been observed that cell sizes in
organisms are fairly well correlated with their DNA contents. So if you
can get an idea of the sizes of any cells in a fossil organism you can
estimate its DNA content. In plants, this has been done by looking at
fossil stomata. In dinosaurs, you look at the cavities left in bones by
osteocytes.

When this was done, it was found that extinct theropods had small cells,
and thus small genomes, comparable in size to bird genomes. In contrast,
ornithischians had larger genomes, comparable in size to other amniote
genomes. Only one sauropod was examined, so we can't tell, given the
high noise level, whether the change happened at the base of theropods
or the base of saurischians. But Herrerasaurus has one of the smaller
inferred genome sizes in their list.

Cool stuff.