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

Re: attack on dinosaur--horrific video

I remember it was thought not too long ago that end K dinosaurs were the
largest of their particular clades (e.g., _T. rex_). Your data doesn't show
this?

Well... the dataset I had, analyzed with the rather primitive method I used, said there was a trend to increased size, but only in the Late Cretaceous, and not for all clades (for example, I did not find any trend whatsoever in sauropods or even sauropodomorphs as a whole). Said method cannot distinguish between the effects of time and phylogenetic inertia, so chances are good I'll find even fewer trends next time.

And then, of course, I can't imagine the size difference between *Daspletosaurus* and *Tyrannosaurus* can be explained by selection for nest defense.

Due to an amazing system of connective tissue supports, a fetus has
virtually no impact on a mother's ability to run away--except at the very
end, of course.


Well, weight.

Amazing...the mother coughs up the joey? 

Yep.

What is that muscle? 

No idea what, if anything, it's homologous to. It's a muscle in the pouch.

Truly an amazing aspect of marsupial reproduction. But the whole point--teleologically-speaking--of placental reproduction is investment--that a few gifted offspring are better able to move more genes into more future offspring than r strategist, albeit r strategists flood the reproductive scene with many disposable units.

Sometimes. Sometimes not! This is why both K- and r-strategists still exist. It's also why there's a wide variety of strategies within placentals and within marsupials (in the former, compare mice and men; in the latter, the koala and the Tasmanian devil).

In a stable environment, K-strategists have an advantage. r-strategists, on the other hand, have an advantage in unstable environments -- as well as in environments that have suddenly become unstable (mass extinction events).