Some Large Dinosaurs Survived the K-T Extinction

mmmscience sends along coverage from the Examiner on evidence that some dinosaurs survived the extinction event(s) at the end of the Cretaceous period. Here is the original journal article. "A US paleontologist is challenging one of the field's greatest theories: the mass extinction of dinosaurs at the end of the Cretaceous period. Jim Fassett, a paleontologist who holds an emeritus position at the US Geological Survey, recently published a paper in Palaeontologia Electronica with evidence that points to a pocket of dinosaurs that somehow survived in remote parts New Mexico and Colorado for up to half a million years past the end of the Cretaceous period. If this theory holds up, these dinosaurs would be the only ones that made it to the Paleocene Age."

Comments

Re:Cavemen?

[nephridium]

So does that mean skimpily clad cavewomen really *did* ride around on dinosaurs? mmmm...

Not really. It says they made it to the "Paleocene", i.e. the epoch adjacent to the Cretaceous. To have meet any cavemen they'd have had to survive through the Eocene, Oligocene, Miocene all the way to the Pleistocene era. That would still be around 60 million years.

I also highly doubt cavemen (or cavewomen for that matter) had the skill or technology to time travel back to the Paleocene. Afaik only genetically enhanced laboratory mice can do that.

Re:Cavemen?

[flyingsquid]

More evidence is always good, but once you actually start to think about it, "a small population of some dinosaurs survived in remote areas until it eventually petered out" is actually more plausible than "every single last dinosaur died at once in a gigantic catastrophe that nevertheless was not large enough to affect other animals such as mammals to the same extent". Many kinds of animals survived, after all. Why shouldn't dinosaurs have, too? I'm certainly not saying they must have, but just on the face of things, it seems more likely that their extinction was gradual and drawn-out over a long period of time. (And yes, I know the K-T extinction is not thought to have happened in the blink of an eye, anyway, but you know what I mean.)

It's a bit telling that the study is published in an obscure web-only paleontology journal called "Palaeontologica Electronica". I'm not saying that good work can't be published in obscure journals, but I would argue that if you had really strong evidence for post-Cretaceous dinosaurs, you wouldn't publish it in a journal that nobody's ever heard of. You'd be publishing in Nature, Science, or PNAS. That suggests that he published here because he didn't have a lot of options, because the scientific community was pretty unreceptive to evidence presented in this study. Obviously, the conventional wisdom isn't everything. Geologists hated the idea of continental drift, and the asteroid impact hypothesis got a very cold reception before the Chicxulub crater was found. But it's worth asking whether the evidence here is any good or not.

First off, it's not as if they've suddenly discovered dinosaurs where nobody expected them. Paleontologists have known for decades that these rock beds contain dinosaurs (as well as typical Cretaceous mammals). It's just that everyone else has always interpreted these rocks as being of Cretaceous age, rather than post-Cretaceous. What he's doing is arguing that the rocks are older than we thought.

Second, what's his evidence for saying these are post-Cretaceous rocks? The best evidence would be a marker bed- if you could show that a skeleton lay above the iridium layer formed by the fallout of the asteroid, then it would be pretty much unrefutable. However, the iridium layer has *not* been recognized in this area. The second best evidence would be a layer of volcanic ash which can be dated using radioactive dating. There are no ashes under the bones which are younger than 65.5 million years old (the date of the impact). In fact all the ashes under the bones are around 75-73 million years old. So his evidence is the pollen grains. He says they look like post-Cretaceous pollen, not Cretaceous pollen. That doesn't seem terribly convincing in my mind. Given that the mammals seen in the same rocks are pretty clearly Cretaceous type mammals, the fossil evidence is contradictory here. His other evidence is something called magnetostratigraphy- the Earth's magnetic poles reverse every few hundred thousand or million years, with series of normal and reversed polarities. If you can match up a series of polarity changes, you can *sometimes* figure out how old the rocks are. But it's not a very precise method, and it's a bit tricky to figure out where a particular sequence going "normal-reversed-normal-reversed" fits into the geological record. It's a bit like trying to figure out the time and date by whether your neighbor has his house lights on or off, or whether the trash has been picked up recently or not.

In short, it would take a lot more than this one paper to overturn the consensus that has resulted from one hundred years of scientific research. I mean, if someone published an experiment tomorrow saying that Einstein was wrong, what would your reaction be? To reject Einstein? Or to think that the experimenter might have screwed up? Currently, the bulk of the evidence says that the extinction took place 65.5 million years ago, and that (with the exception of birds) the dinosaurs didn't make it.

Re:Cavemen?

[Patch86]

Oh. You want cites? Ah.

Look! A bunny! Look at the bunny! (runs away)

Oh come one, that's not even trying...

http://en.wikipedia.org/wiki/Tyrannosaurus#Skin_and_feathers