buckshot23

Before I ask my question this is not a "silver bullet" argument. I was just wondering about it. Now the question...
Let's use the Coelacanth as an example of a "living fossil". From my understanding the Coelacanth was thought to of went extinct about 70 million years ago. Because it had never been seen alive and not discovered in rocks younger than 70 million years. Now that we know it lived those 70 million years. The question is how could this fish live and not leave any fossil evidence that it lived during that time period?(assuming they still have not been found in younger rocks) I am quite sure this has been addressed before but I wanted to see how reasonable the answers were.

Godless Wonder

If talkorigins.org or the book it refers to can be trusted:

http://www.talkorigins.org/origins/postmonth/sep02.html

Lots more details if you follow the link.

buckshot23

Where are its fossil decendents?

actually read that page before posting. I do not think they are exactly the same but very very similar.
from here

Godless Wonder

Good question, and I'm no expert there. From what I understand, fossilization is a rare thing. We're lucky to have the fossils we do have.

As I understand it, the modern variant of the coelacanth is not exactly common. Should we expect its fossils to be common?

dmarker

However, evolutionary theory is not dependent on fossil evidence.

buckshot23

Maybe not. However they must of been billions of them that lived in that 70 million years. Seems like we would of found something. :huh:

buckshot23

So are you saying the fossil record does not support darwinism? Or just that it is no longer needed?

RBH

The estimates I have seen suggest that 1 in 1000 species that have lived have been found as fossils.

One other remark. Distinguish between "not leave any fossil evidence" (buckshot23's locution) and "we have not (yet) found fossils of" (reality). While estimating populations is difficult given the depths at which coelacanths live, some have estimated as few as some hundreds of coelacanths are actually down there. Even if it's a thousand, the high estimate, that's far from a lot. Given the taphonomy of deep sea fossililzation, and given that there are damned few coelacanths around, that more fossils haven't been found is not at all amazing.

How many people does buckshot23 imagine are looking for fossils of coelacanths, would recognize them in matrix when they saw one, and would have the skill to remove it? We have relatively few specimens of many animals that were almost certainly orders of magnitude more common than coelacanths.

Finally, that we have "living fossils" -- living animals once thought to be extinct -- merely means that new data came in. It has zippo to do with the theory of evolution one way or the other.

RBH

Donnmathan

Just a layman's knee-jerk answer, but let me try to put together a scenario -

1) Most of the marine fossils we've got are from upheavals of ocean bottom, or places where what is now land was once under water. Such actions do take time, so the incidents of younger marine fossils are likely rare, as the rock they are in takes time to a) be pushed to the surface, and b) be erroded to the point where the fossils are reachable.

2) Coelacanth, if I recall correctly, are deep-water fish, so the time needed for point 1 above is much longer, if it happened at all...remember, the areas they lived in would have to have surfaced in that time, too. That just might not have ever happened.

3) Of course, fossilization is not fantastically common, either...they just might have had a small population, and we've just never found the fossils. New species are being found every year, so this quite possible, really. Add to that the distinct possiblility that they were living atop an area of vulcanism, or plate subversion, and there simply may be few or no fossils to find!

So...you may be asking for something that has every reason not to exist in the first place, and even if it does, it may be incredibly rare or under hundreds of feet of ocean bottom under thousands of feet of water! Not so hard to imagine why we don't have fossils after a certain point. Oh, and if anyone who ISN'T a layman would care to correct/clarify any of my suggestions, please do!!

JLK

Ha. While I was composing this, RBH and Donmathan beat me to it.
Submit Message anyway.

Coelacanths underwent an enormous diversification in the early Carboniferous and, like many species, suffered widespread extinctions in the Permian. The deeper lobe-finned genera are likely to have been the only ones that colonized deep water (there are even 7 known genera of fresh water coelacanths) and the huge loss of continental shelf that accompanied the late Permian mass extinction left only the deep water survivors to found the post-Permian lineage. The survivors were morphologically closer to the original coelacanth stock, but they are not in any way identical (modern coelacanths are even more different from older coelacanthiform). Besides small population size, the floor of the vast stretches of deep ocean is in general a more difficult place for fossilization to occur relative to continental slope waters (I'll let you puzzle out the reasons).

This same phenomenon can be seen in trilobites where extinction caused severe constriction of diversity such that almost all post-Devonian forms spread from a very few lineages.
A new c. species was discovered in Indonesia in 1998 (Latimeria menadoensis) that shows strong differentiation from the previously known species 10,000 kilometers away in Comoro (L. chalumnae). These two populations are obviously far apart enough to be in separate breeding populations. Since the two populations are small and isolated and occupy different ecological niches, differentiation between the populations has occurred over time. Researchers can approximate thru genetics when the two species differentiated from their common ancestor. Pouyad et al. estimate the divergence time was about 1.2 - 1.4 million years ago.