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FW: Rapetosaurus stuff



Folks,
 
Jon Wagner asked me to forward these comments to the list:
 
-----Original Message-----
From: kritosaurus [mailto:kritosaurus@netzero.net]
Sent: Friday, August 03, 2001 2:02 PM
To: tholtz@geol.umd.edu
Subject: RE: Rapetosaurus stuff

    (Dr. Holtz: Would you please forward this to the list?)
 
    Dr. Holtz wrote:
>Lehman looks at Judithian (updating his 1997 paper in DinoFest), adds the
>Edmontonian, and the Lancian (updating the 1987 paper).
    As a former student of Dr. Lehman, I had the opportunity to review an early draft of this paper. I had some minor disagreements with specifics of the hadrosaur biogeography, and I am eager to see how and if they are handled in the final draft:
 
>For the Judthian, he finds a southern Kritosaurus-Parasaurolophus fauna (in
>both upland and lowland),
    As of now, "upland Judithian" evidence is limited in the Big Bend region, although this will change a little. As may some of the taxa...
 
>a northern lowland Corythosaurus-Centrosaurus
>fauna, and a northern upland Maiasaura-Einiosaurus fauna.
    Having looked at a little of Horner's recent stratigraphic work, I am becoming skeptical of the interpretation of Maiasaura as an "upland" animal. A more defensible "upland" Montana hadrosaur would be Prosaurolophus or Hypacrosaurus.
 
>The Edmontonian
>(admittedly more poorly studied) includes survival of a
>Kritosaurus-Parasaurolophus fauna in the south,
    This is based on interpolation: there does not appear to be a discrete "Edmontonian" fauna in Big Bend, and the San Juan Basin fauna apparently straddles the J/E boundary. The best working hypothesis is that the "Judithian" faunas continue uninterrupted through to the "Lancian" boundary. What happens there is a big question.
 
>an upland
>Pachyrhinosaurus-Edmontosaurus fauna in the Montana-Alberta border region,
>and an Anchiceratops-Saurolophus fauna further north in Alberta.  His
    I am VERY hesitant about this interpretation. All previous interpretations of "Edmontonian" facies associations suggest that Edmontosaurus is the LOWLAND component, and Saurolophus that UPLAND component of this faunal structure. There is, however, evidence to suggest that the "upland" association *may* be ancestral for the Edmontosaurus clade.
 
    As for the Lancian, the picture of southern Late Maastrichtian faunas is becoming steadily more focused. Be prepared for substantially LESS commonality with northern faunas than previously reported.

    Despite my minor disagreements, this paper is pretty much the state-of-the-art in latest Cretaceous North American biogeography. It should be clear that the primary areas of ambiguity, and therefore the most important for exploration, are on the "fringes" of the well-known Albertan and northern Great Plains strata, including New Mexico, Arizona, Texas, and Mexico in the South, California in the West, northern Canada and Alaska to the North. Anything from the East would be more than welcome. In all of these "fringe" areas, a very important element of research is stratigraphic. It is clear that there is a dense, multifaceted biogeographic story; vertebrate biostratigraphy, especially using dinosaurian faunas, introduces a profound potential for circular reasoning. I would add that tentative referrals of fringe area specimens to well known taxa from well known regions, such as the "Big Bend T. rex," should NEVER be used for more derived studies such as biogeography. The only way to remove such question marks from the data is by further prospecting and study, not by "wishing" taxa into new localities. Not that I am not guilty of this myself on occasion... :)
Jonathan R. Wagner
9617 Great Hills Trail #1414
Austin, TX 78759 
------------------------------------------
                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742      
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
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