[dirtboy]

I disagree with the accessment. Crododilians, after all, lay their eggs out of water and rely on the sun to incubate them.

My take on the extinction of the dinosaurs? It wasn't an extinction. Megafauna dinosaur forms died out, but birds, the small fauna form of dinosaurs, survived and thrived, and mammals took over the megafauna niches.

[Eric in the Ozarks]

Liberals, like the dinosaurs they are, often eat their young.

[Junior]

...and mammals took over the megafauna niches.

Believe it or not, the initial successors in the megafaunal niches were birds. Of course, that didn't last long...

[Ichneumon]

My take on the extinction of the dinosaurs? It wasn't an extinction. Megafauna dinosaur forms died out, but birds, the small fauna form of dinosaurs, survived and thrived, and mammals took over the megafauna niches.

A problem with that hypothesis is that there were plenty of "microfauna" dinosaurs too (non-bird variety), and they died out as well.

[capitan_refugio]

"My take on the extinction of the dinosaurs? It wasn't an extinction. Megafauna dinosaur forms died out, but birds, the small fauna form of dinosaurs, survived and thrived, and mammals took over the megafauna niches."

You have a point. I, too, consider birds to be the dino legacy. However, the Cretaceous extinction did happen, and the paleontological evidence is indisputable. Many, many genera disappeared at, or near, the end of the Cretaceous. Vertebrate paleontologists, such as Robert Bakker, point out that the large dinosuars were in decline for some time prior to the Cretaceous/Tertiary (K/T) boundary. In fact, early large dino forms died out at the Jurassic/Cretaceous boundary!

I have a book on the K/T boundary that I purchased at a geological convention a few years ago. I am convinced that there is evidence for dinosaurs geologically above (younger than) the so-called asteroid impact iridium layer of Alvarez, et al., 1980. The asteroid impact may very well have happened, and may have had significant climatological effects, but it doesn't explain everything about the K/T extinction. Though the dinosaurs were greatly impacted, lizards, snakes, turtles, and crocs survived.

For instance, why did the ammonoids completely die out and yet, their close cousins, the nautiloids, survive? Why did many species of plants die out, and yet others that occupied similar niches survive? Why did the rudist bivavles go extinct as compared to the other bivalve genera?

I am very familiar (professionally) with the micropaleontology of the K/T boundary. Many diatoms, nannoplankton, and forams suddenly disappear, while others remain abundant. It can not all be accounted for by ecological niche or geographical distribution.

I suspect that with the terrestrial lifeforms, climate change, loss of habitat, and disease contributed greatly. I can easliy imagine a species or genus becoming so enfeebled that it cannot continue on. With the aquatic forms you can add change in ocean chemistry as a causitive factor. This is especially true with the micro-assemblages. Maybe what is most remarkable is that mammals and amphibians sailed right through. Why so? How were they better able to adapt?