New Dinosaur Species Is a Missing Link

An anonymous reader writes "A new dinosaur provides a link between what paleontologists consider 'early' and 'later' dinosaurs. There's a gap in the fossil record between the oldest known dinosaurs, which walked or ran on their hind legs about 230 million years ago in Argentina and Brazil, and other predatory dinosaurs that lived much later. Daemonosaurus chauliodus helps fill in a blank in dinosaur history."

Comments

And now there are TWO gaps!

[Anonymous Coward]

And now there are TWO gaps!

"Daemon"osaurus?

[TheABomb]

Did it run on Linux?

Sorry, but it is /., so I had to ask.

Species 404?

[PPH]

The missing link?

Now there are two gaps ..

[jc42]

In the ongoing "discussion" with the creationists, it has occasionally been pointed out that whenever a biologist finds a fossil that fills in a gap in the fossil record, one result is to replace the one gap with two gaps. Thus, no such discovery can ever persuade the creationists; it just adds to their list of known gaps in the fossil record To them, evolutionary theory can't be ready for prime time until all the fossil gaps are filled in. They don't acknowledge the patterns that biologists find in the (admittedly very sketchy) fossil record.

Re:Now there are two gaps ..

[Anonymous Coward]

Cos they get on our school boards and tell our kids what to think.

Re:Now there are two gaps ..

[c6gunner]

For example we keep finding primate fossils that are very close relatives to man. Unfortunately, we have never found a fossil that is a direct ancestor of man. All we can say is that man and whatever fossil shared a common ancestor.

Homo Heidelbergensis
Homo Antecessor
Homo Erectus
Australopithecus Afarensis
Ardipithecus

How far back do you want to go?

It's rather irrelevant, anyway. Let me rephrase your complaint:

"You've shown me two of your cousins, five of your brothers, three of your sisters, two uncles, and a niece. But you can't show me your mother or father, so clearly you were miracled into existence."

Yep. Makes perfect sense.

Re:Now there are two gaps ..

[cbhacking]

Exactly. The process of evolution is gradual. Speciation doesn't occur in a single generation, or even in a single lifetime.

Consider equines. Horses and donkeys clearly share an evolutionary ancestor. In fact, they haven't even completely diverged from that ancestor; despite "obviously" being different species, they are inter-fertile. The offspring (mules) are infertile, so it is reasonable to call horses and donkeys different species; they can produce live offspring, but those offspring are a genetic dead end.

OK, how does that relate to my point? Well, sometime many millennia ago, there were a group of equines that, although not exactly like today's donkeys, were close enough that you would call them donkeys. There was a similar group of "horses". Here's the weird thing: they were the same species (interfertile and producing viable offspring). Somewhere over the millennia since then, the two groups, breeding primarily within their own group and not between groups, reinforced certain traits to the point where cross-group offspring were no longer fertile.

The question for you: how the heck do you define where speciation occurred? Was it when the (still interfertile) groups started moving apart? Was it the first member of each group that could not produce fertile offspring with more than half the potential mates in the other group? Was it when there was one member of each group which were mutually incapable of producing fertile offspring with any descendents of the other? For that matter, how do you define thr groups themselves? There were probably some fertile proto-mules for a while, which didn't fit cleanly into either group. They either died out without reproducing or were merged back into one of the groups, the line would nonetheless have been somewhat blurry.

Now, next question: how do you determine, from the fossil record, where that speciation occurred? Which of a bunch of old horse/donkey-skeleton-like rocks (that's all fossils are) was once an animal that gave rise to modern horses which can't produce fertile offspring with modern donkeys? How do you distinguish, from the fossils, that it was X, and not the parents of X, or the children of X, or possibly the specific children of X by Y? How do you distinguish that it was X and not X's sibling that got a slightly different set of chromosomes and was no longer able to produce fertile offspring with his or her corresponding member of the other group, yet went on to breed successfully and pass those chromosomes onto the other members of the group?

Seriously, demanding to see "direct ancestors" in the fossil record is absolute stupidity. I'm no biologist (as I'm sure any biologist reading my post noted) but I understand enough basic genetics to know that even with genetic evidence it's non-trivial to trace direct ancestry, and without it the task is nearly hopeless. Combine that with the way that most individuals never get fossilized, much less last long enough after fossilization to be found today (never mind the many fossils that we don't have yet; new finds are still occurring). Given all that, it'd be a minor miracle to have gaps of only 1000 generations in a direct chain of ancestry. That's enough generations for some pretty significant changes, when you're looking for incremental differences between a horse and a donkey. 1000 generations ago, your ancestors were recognizably human, but they still looked different enough from you today that you wouldn't have been able to call them a "direct ancestor" or not from fossilized bones - and they were probably still close enough that you'd have been interfertile!

New* Dinosaur Species

[FiloEleven]

*For very old values of New.