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Re: Any Puter Experts That Can Help biology dept., duke
mel turner (mturner@snipthis.acpub.duke.edu) 2004/03/06 05:13
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From: mturner@snipthis.acpub.duke.edu (mel turner)
Newsgroups: alt.fan.uncle-davey
Subject: Re: Any Puter Experts That Can Help
Date: Sat, 6 Mar 2004 12:13:41 +0000 (UTC)
Organization: biology dept., duke
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Xref: news.nzbot.com alt.fan.uncle-davey:2936

Apolgies if two or more copies of this come through;
I sent it but it didn't appear, although other posts did.

An earlier, similar reply to the following was apparently lost in the
aether. If it eventually turns up, my apologies for the duplication.

In article <c271vr$7q2$0@pita.alt.net>, noway@jose.com [Uncle Davey] wrote...

>wiadomoci news:c24ueu$om0$1@gargoyle.oit.duke.edu...
>> In article <c245k7$a68$0@pita.alt.net>, noway@jose.com [Uncle Davey]
>wrote...

[snip]
>> >You raise a good point, how many loricariid fossils are there?
>>
>> More than zero; I recall finding refs to some when looking for
>> info on Corydoras fossils for you in that thread a while back.

[snip of  a few fossil catfish refs]

>Once again, not very many fossils seem to have been located bearing in mind
>the toughness of the exoskeleton of Loricariids and the length of time they
>must ahve been around.

I'm not sure that we should really expect that the currently-known
fossil record of Loricariidae [or Callichthyiidae] should be any
better than it is.

First, it seems that there aren't any large number of South American
freshwater fossil sites of the right age range that have been
extensively explored so far. How many fossil catfish experts are
currently working to actually study whatever remains have been found
to date? For all we know, there may in fact be many more fossil
armored-catfish specimens already on museum storage shelves but
still waiting to be described and named.

Then, there are the obvious taphonomic questions:

Don't many loricariids prefer to live in rocky stream habitats, not in
places with deeply accumulating sediment?  I vaguely remember
something of the sort. If it's the case that living loricariids tend
to avoid those places that favor fossil preservation, then it may not
be so surprising that the known fossils of their relatives are
relatively few.

From what I've seen so far about the loricariid and callichthyiid
fossil record, it sounds like members of both families often tend to
disintegrate into a jumble of loose plates and spines after death.
[An aquarist might confirm if this often happens to ones that die
several days before being discovered and removed?]  Even if the
scattered bits of armor do preserve well, the hypothetical overworked

South American paleoichthyologists might be forgiven for not spending
much time classifying the fragmentary remains. I'm reminded of that
earlier-cited paper which mentioned layers with concentrations of
abundant Corydoras plates and spines, but evidently didn't bother to
name any new fossil Corydoras species from the remains. The literature
already cited of fossil loricariids and callichthyiids do seem to
largely involve descriptions of loose bones [other than your one very
complete Corydoras fossil].

Anyway, it seems to me that the currently-known existence of even a
few fossil speciments and species of these fish strongly implies the
existence of many more individuals [and additional  related species]
that aren't yet known as fossils. Presumably, that fossil Corydoras
species known only from a single specimen must represent only one of
a very large number of individuals that ever lived of that species.
[But I suppose a believer in special creationism might argue that that
one fossil fish may well have been the only individual ever created of
its species, and a true believer in omphalism might even suggest that
it was specially created as a fossil, already in place in the rocks]

Even an adherent of inclusive separately-created "kinds" would need
to argue that there are many "gaps" in the fossil record between say,
the remarkable modern diversity of Corydoras catfishes and the
hypothetical originally-created single ancestral form of their "kind".
The explanation will be much the same as the "evolutionist" one-- all
the required gradual-intermediate forms must have existed in the past,
but are as yet unknown as fossils.

cheers




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