Re: Fossil Records Show Biodiversity Comes and Goes

From: John Harshman (jharshman.diespamdie_at_pacbell.net)
Date: 03/18/05 

Date: Fri, 18 Mar 2005 15:07:07 GMT

George wrote:

> "John Harshman" <jharshman.diespamdie@pacbell.net> wrote in message
> news:f4p_d.24049$OU1.16623@newssvr21.news.prodigy.com...
>
>>George wrote:
>>
>>
>>>"John Harshman" <jharshman.diespamdie@pacbell.net> wrote in message
>>>news:jdm_d.11493$C47.1931@newssvr14.news.prodigy.com...
>>>
>>>
>>>>George wrote:
>>>>
>>>>
>>>>
>>>>>"John Harshman" <jharshman.diespamdie@pacbell.net> wrote in message
>>>>>news:zah_d.19652$Pz7.12562@newssvr13.news.prodigy.com...
>>>>>
>>>>>
>>>>>
>>>>>>George wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>"John Harshman" <jharshman.diespamdie@pacbell.net> wrote in message
>>>>>>>news:HS9_d.23911$OU1.23670@newssvr21.news.prodigy.com...
>>>>>
>>>>>
>>>>>>>The paper I linked you to earlier that you thought irrelevant indicated
>>>>>>>otherwise . Oh, by the way, an insect that has been highly successful,
>>>>>>>and
>>>>>>>is
>>>>>>>quite the generalist is the common cockroach.
>>>>>>
>>>>>>The paper was irrelevant to what we were talking about there, but it's
>>>>>>relevant to what we are talking about here. And actually it refutes your
>>>>>>claim. The more specialized groups were not more vulnerable to
>>>>>>extinction (as groups), thoug species turnover in those groups was
>>>>>>higher than in generalists. Didn't you read the paper? What was your
>>>>>>point about cockroaches?
>>>>>>
>>>>>
>>>>>No, actually it doesn't refute my claim because you somehow assumed I was
>>>>>talking about extinction of entire clades, when I was talking about
>>>>>extinctions
>>>>>across the clades of species that were specialists. The paper made it clear
>>>>>that species turnover was higher in the specialists than in the generalists,
>>>>>as
>>>>>you just pointed out, and which was my point.
>>>>
>>>>No, that's not your point. Or if it is, then you point makes no sense.
>>>>You need to have a higher net extinction rate among specialists to make
>>>>your story work -- they get overspecialized, they die out. If high
>>>>extinction is coupled by high speciation, there's no net extinction,
>>>>just turnover, and thus no loss of diversity.
>>>
>>>
>>>http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_60408.htm
>>>
>>> UNIFORM EXTINCTION WITHIN CLADES OF THE MIDDLE PALEOZOIC CRINOID
>>>MACROEVOLUTIONARY FAUNA IN THE NORTH AMERICAN MIDCONTINENT
>>> KAMMER, Thomas W., Geology and Geography, West Virginia Univ,
>>>Morgantown,
>>>WV 26506-6300, tkammer@wvu.edu and AUSICH, William I., Geological Sciences,
>>>The
>>>Ohio State Univ, Columbus, OH 43210
>>> Global crinoid generic diversity reached its Paleozoic maximum during
>>>the
>>>lower Visean (Lower Mississippian). Diversity subsequently declined 75
>>>percent
>>>by the upper Serpukhovian (Upper Mississippian). This decline was accompanied
>>>by
>>>a change in clade dominance patterns as the camerate-dominated Middle
>>>Paleozoic
>>>crinoid macroevolutionary fauna transitioned to the advanced cladid-dominated
>>>Late Paleozoic crinoid macroevolutionary fauna. Various hypotheses, relating
>>>to
>>>rapid faunal turnover or increased predation, have been proposed to explain
>>>this
>>>evolutionary event that took place during a time when the biosphere was
>>>experiencing only background extinction.
>>>
>>> In the North American Midcontinent this transition took place by the
>>>early
>>>Chesterian. What happened during the Meramecian? The Middle Paleozoic fauna
>>>was
>>>well established in the preceding Osagean with camerates near their peak
>>>Paleozoic diversity, although advanced cladids had already started their
>>>radiation. Data for the Midcontinent indicates that all the major crinoid
>>>clades
>>>(camerates, advanced cladids, primitive cladids, disparids, and flexibles)
>>>declined in diversity by about half without a significant change in clade
>>>dominance patterns between the Osagean and Meramecian. This suggests uniform
>>>extinction across clades as taxa were exposed to extinction stresses such as
>>>habitat reduction or increased predation. All clades were free to radiate
>>>once
>>>extinction stresses were reduced in the Chesterian. The fact that the
>>>advanced
>>>cladids were the only clade to radiate suggests they were better adapted than
>>>other crinoid clades. Presumably this reflects the unique muscular arm
>>>articulations of this clade, which was also the ancestral clade of the
>>>articulates, the only post-Paleozoic crinoids.
>>>
>>> The existing global database (Sepkoski, 2002) does not strongly support
>>>the pattern of uniform extinction as seen in North America. Currently we are
>>>collecting global data to better understand why the North American record is
>>>unique. We will attempt to test whether the persistence of the preferred
>>>habitat
>>>of camerates during the Meramecian may have extended the Middle Paleozoic
>>>crinoid fauna longer in this region while simultaneously restraining the
>>>radiation of the advanced cladids.
>>
>>Why do you persist in posting these irrelevant abstracts? What, aside
>>from being about crinoids and extinction, does this have to do with
>>anything we're talking about?
>>
>>[snip]
>
> It supports what I was talking about with regard to extinction within crinoid
> clades that occurred in the Mississippian.

No it doesn't, unless all you want to claim is that there was some
extinction within crinoid clades in the Mississippian. There's nothing
about differential extinction in specialized as opposed to
nonspecialized species, or any of the other stuff you have proposed.

>>>>What international body would do that recognizing? No such body exists.
>>
>>I really would like to know what you were talking about there. Could you
>>reply?
>
> Whatever. The point is that a lot of people have accepted the notion that
> dinosaurs and birds are likely related.

No, that was my point. Your point was that it wasn't "officially
accepted", and I asked who the official acceptor would be. If you're
going to backpedal, have the grace to admit it.

> I don't have a problem with that.
> Having said that, it isn't something that is set in concrete. There are still a
> lot of questions that haven't been answered.

Such as?

> In addition, since, as I've said
> before, there is such a dearth of early bird fossils, my view is that the
> question of birs origins hasn't been resolved. Do I think it is most likely
> that birds evloved from dinosaurs? I think it is likely. Byt that is just an
> opinion.

You could back up that opinion with plentiful data if you chose to look
at the literature. There is quite a wealth of early bird fossils these
days, and of near-birds, and of feathered non-birds, and such, largely
from Liaoning. If you ask me, Microraptor gui all by itself is pretty
conclusive.

>>>John Ostrom doesn't say that they are dinosaurs. He says that they are
>>>related.
>>
>>That's a matter of taxonomic convention, not relationships. In fact
>>Ostrom said that the closest relatives of birds were dromaeosaurs, which
>>would make birds nested well within Dinosauria. Only if you artificially
>>remove birds, making Dinosauria paraphyletic, are birds not dinosaurs.
>>Make no mistake: Ostrom says that birds are much more closely related to
>>some traditional dinosaurs than those dinosaurs are to other dinosaurs.
>
> That's probably true. But as I've already said, with the dearth of bird
> fossils, I'm not ready to fully commit. Sorry. I'd prefer to see more fossil
> evidence.

I'm at a loss to imagine what more fossil evidence would be required. We
have pretty much all imaginable fossil intermediates right now. M. gui
even closely resembles the hypothetical "Proavis".

>>>>>Like I said above, I won't go there until those in higher places make the
>>>>>decision to include birds in the dinosauria, and it gets generally accepted.
>>>>
>>>>Who are these people in higher places? Who says it's not generally
>>>>accepted, and how would you know if it were?
>>>
>>>I read the same journals you read. Or least some of the same one.
>>
>>Yes, and what are you reading in those journals that leads you to think
>>there's any doubt about birds being dinosaurs? Also, please tell me who
>>these "people in higher places" are.
>
> Higher places that me. Figure of speech. As I said earlier, since birds have
> hollow bones, where are the hollow-boned dinosaurs?

Like I said, many theropods are hollow-boned, so they're right in front
of your face.

> I don't doubt that birds
> are descended from dinosaurs. But I simply would like to see more fossils found
> before I add my full support.

What fossils? What would it take?

>>>>We'll see. The fossil record of birds is pretty bad, but it's not as bad
>>>>as it looks. There are just so few avian paleontologists, and even fewer
>>>>of them are looking in the Mesozoic, and anyway much of the record is
>>>>probably Gondwanan. All that translates into lack of investigator
>>>>effort. At least with mammals you can sieve for teeth.
>>>
>>>Yeah, and with birds pretty much all you have is broken hollow bones. By the
>>>way, where are all the hollow dinosaur bones? Mind you, I have no problems
>>>really, with saying that bird descended from the dinosaurs. It's just a
>>>question that won't go away in my mind.
>>
>>There are in fact a great many hollow dinosaur bones. Many theropods are
>>highly pneumatized, as are some of the bones in many sauropods, though
>>this is almost certainly convergent. If you actually want to look at
>>characters, there are great numbers of published phylogenetic analyses
>>showing birds nested within Theropoda. I don't know of a single analysis
>>(as opposed to vaguely supported claim) in which they aren't. (Though
>>Larry Martin waved one in the air at the Ostrom Symposium, I don't think
>>it was ever published.) Start with Gauthier 1986 and go on from there.
>>Or start with Ostrom's less formal arguments if you prefer.
>
> I've read Ostrom's arguments. I've heard him in person describe the evidence.
> He admits that there are still a lot of questions that are unanswered, and a
> dearth of fossil evidence. We need more fossils.

Um, how long ago was this that you heard him describe the evidence? More
than ten years, perhaps? Twenty years? You don't seem aware of anything
that's happened recently.

>>>>Yes you were. You were talking about extinction of crinoid groups, coral
>>>>groups, and dinosaurs, and your claim was that in all these groups the
>>>>later members became too specialized and thus there was a crash.
>>>
>>>Read the paper I posted above.
>>
>>All the abstract says is that some groups crashed. It doesn't so much as
>>suggest that the crash was due to overspecialization. Is that in the
>>body of the paper somewhere? Hey, wait a minute -- what paper? This is
>>just a GSA abstract. There isn't a paper.
>
> Sorry. I thought you had access to GSA abstracts. I'll try to find the body of
> the paper, but I'm not optimistic.

What body of the paper? It's just an abstract.

>>(By the way, one thing that's always annoyed me about geologists is that
>>they treat GSA abstracts as if they were real citations. I'm sure it was
>>a nice talk/poster, but I didn't go to the talk or read the poster, so
>>it's all lost on me. That's not real publication if all that's available
>>is an abstract.)
>>
>>[snip]
>
> GSA online requires a subscription in order to access full papers. I don't have
> a current subscription to GSA online. Hence, I posted the abstract only.
> Sometimes, those papers are released elsewhere after a period of time, as has
> apparently happened with my Journal of Paleontology paper I posted earlier. I
> will see if I can find the full paper elsewhere.

Dude, it's an abstract of a *talk* or poster given at a GSA meeting.
There is no paper, necessarily. Usually, the research described ends up
being published in a real paper, but that could end up anywhere, at any
time. Or it might never be published. That's the problem: this is a
bare-naked abstract, not attached to anything else; no data, not
analyses, no nothing except an abstract.