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Re: No Hedging.



At 10:58 PM 5/20/98 -0400, John Bois wrote:
>
>
>On Wed, 20 May 1998, chris brochu wrote:
>> This quote indicates some ignorance on Hedges' part
>
>> This quote by Hedges, by the way, is not surprising, given some of the
>> other papers Hedges has authored or coauthored on the subject of
>> molecules-versus-morphology.  Most of the systematics community have come
>> around to saying "molecules or morphology?  Yes!", but he is one of those
>> who would still favor one over the other.
>
>Which of Hedges' statements is ignorant? 
>
>1. Paleontologists hardly ever look for mammals in C. rocks?
>
Yeah, that's damn ignorant.  Mesozoic mammals have been the focus of
research of many, many, many paleontologists, from Owen (who first reported
them), through Marsh & Cope, to G.G. Simpson, Zofia Kielan-Jaworowska, J.A.
Lillegraven, W.A. Clemens, Malcolm McKenna, R. Cifelli, Dasheveg D., Tim
Rowe, Dave Krause, Lou Jacobs, David Archibald, Lev Nessov, etc., etc.

Just because there aren't popular books like "The Complete Multituberculata"
or "Triconodonts: A Global View" or "The Hot-Blooded Dryolestids" doesn't
mean that there isn't a huge body of literature on Mesozoic mammals.  After
all, Mesozoic mammal workers got their "bible" (Lillegraven,
Kielan-Jaworowska & Clemens) a decade before dinosaur workers got theirs
(Weishampel, Dodson & Osmolska).

You don't think that the new Mongolian or Malawi or Madagascan expeditions
were originally started primarily to find dinosaurs, do you?  They had, as
part of their original plans (and remaining as a main topic of search), the
quest to find new and better Mesozoic mammals.

So, yeah, anyone who thinks that paleontologists aren't looking for Mesozoic
mammals is learning their paleontology from watching TV, not from the
scientific community!

(Heck, I've been on undergrad field camps where one of the half-day labs
involves collecting and identifying Mesozoic microvertebrates, including
mammals!  And undergrad or grad students at Yale can earn some lab time (and
maybe some cash) picking Mesozoic mammal teeth out of anthills (a long
story...)).

>2. There was previously not enough convincing evidence for paleontologists
>to invest their time searching?
>
>Does the generally held view that pre K/T mammals lack diversity tend to
>fulfill itself by discouraging research? 

This is not a generally held view.  Check out any textbook on vertebrate
paleontology (from Romer to Carroll to Benton).

>3. Paleontologists presume that modern aspect species sprang into
>existence after the K/T so they don't bother to look?

A different question entirely.  Members of the Ungulata and the
Primatomorpha have been identified in the early Late K and latest K
(respectively), but these don't closely resemble the modern forms, and why
should they?  Tyrannosaurids and ceratopsids don't closely resemble their
Triassic or Early Jurassic relatives, but they are still theropods and
ornithischians.

>4. Mammals might turn up in previously overlooked strata?

Damn straight, and let's hope so!  The more the merrier.

>Ultimately, of course, fossils will arbitrate this particular "molecules
>or morphology" argument.  But only if a reasonable amount of effort is
>invested.  Has this happened?  From the outside I see two extreme
>opinions.  Hedges saying no one has looked, and others 
>saying words to the effect of: "We have found all the pre-K/T mammals we
>are going to find."

Apparently the view from the outside could use some Windex...

Okay, you admit these are extreme opinions.  Neither is correct, and neither
reflects the actual state of affairs in Mesozoic mammalian research.

>I respect your opinion--that genetic change doesn't
>necessarily create morphological change.  But it is just an hypothesis.
>In this case it should enjoy no higher ground than the claim: genetic
>change led to morphological but we just havent found the bones yet.

John, I strongly suggest you pop down to McKeldin Library, check out Chris'
hallmark paper on gavial origins and the molecules and morphology question
(in Systematic Biology: it was still on the new journal shelves last week),
and read.  sorry I don't have the volume, issue, or page numbers handy.

Brochu's "opinion" is a very well tested hypothesis.  He is one of the most
knowledgeable people in this aspect of evolutionary biology, since he has
bothered to test these propositions in a particular branch of the vertebrate
tree (crocs).

>So
>just to be on the safe side, shouldn't we look for them?  Unless we
>already have, of course.

Of course.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661