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RE: Dinosaur-relevant article for you statistics gurus



> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On Behalf Of
> Phil Bigelow
> Sent: Sunday, August 15, 2004 8:36 AM
> 
> On Sat, 14 Aug 2004 08:45:24 -0400 "Andrew A. Farke"
> <andyfarke@hotmail.com> writes:
> 
> > In their presentation of the data, I'm pretty horribly confused
> > (although if
> > I go back to the Sheehan paper, which I don't have with me at home,
> > perhaps
> > it would clear things up. For instance, their data table gives a
> > listing of
> > "Number of dinosaur species per family in three Cretaceous periods."
> > The
> > periods are divided into Upper, Middle, and Lower. For ceratopsians,
> > they
> > list 50 species in the upper, 53 in the middle, and 19 in the lower!
> > I
> > wonder if they are talking about specimens, instead. Anyone have the
> > Sheehan
> > paper handy to confirm this?
> 
> Sheehan et. al (1991) don't talk about any other units (nor other times)
> other than the Hell Creek Fm. (all of it uppermost Cretaceous).
> Furthermore, they (1991) counted "minimum number of individuals" (meaning
> that if two bones are found in close proximimity and belong to the same
> family, then the two bones were counted as one individual).  Sheehan et
> al. only recognized elements down to Family level (although they provided
> a table (Table 2) which lists the number of genera within each family in
> the Formation.  In the case of Ceratopsidae, they list 2 genera for the
> Hell Creek Formation).  Species are not dealt with.
> 
> They *do* break the Hell Creek Formation down into three stratigraphic
> units (upper, middle, and lower).  Perhaps that is where the confusion
> lays?
> 
> Reference:
> Sheehan, P. M., (and four others). 1991.  Sudden extinction of the
> dinosaurs: latest Cretaceous, Upper Great Plains, U. S. A.   Science
> 254:835-839.

Thanks for checking on this--it does indeed look like the authors of the
stats paper were just a little sloppy in how they presented their data.

Andy