RE: Bakker's Brontosaurus and Late Cretaceous populations

[Denver Fowler <df9465@yahoo.co.uk>]

--- Ken.Carpenter@dmns.org wrote:

> > (noone ever suggested hadrosaurs and 
> > lambeosaurs were male-female,
> 
> Nopcsa suggested this in 1929

As usual I stand corrected. Although my point still
stands valid.

Thanks Ken,

Denver.


> 
> Kenneth Carpenter, Ph.D. 
> Curator of Lower Vertebrate Paleontology 
> and Chief Preparator 
> Department of Earth Sciences 
> Denver Museum of Nature & Science 
> 2001 Colorado Blvd. 
> Denver, CO 80205 USA
> 
> Ken.Carpenter@DMNS.org
> ph: 303-370-6392/ or 6403 
> fx: 303-331-6492 
> 
> for PDFs of my reprints, info about the Cedar Mtn.
> Project, etc. see:
>
https://scientists.dmns.org/sites/kencarpenter/default.aspx
> for fun, see also:
>
http://dino.lm.com/artists/display.php?name=Kcarpenter
> 
> 
> 
>  
> 
> > -----Original Message-----
> > From: owner-dinosaur@usc.edu
> [mailto:owner-dinosaur@usc.edu] 
> > On Behalf Of Denver Fowler
> > Sent: Tuesday, August 02, 2005 7:35 AM
> > To: dinosaur@usc.edu
> > Subject: RE: Bakker's Brontosaurus and Late
> Cretaceous populations
> > 
> > Tom Holtz wrote:
> > 
> > In one of the episodes Bakker explains why he
> > > doesn't
> > > > feel that a comet killed the dinosaurs, One
> thing
> > he said
> > > was
> > > > that before their sudden disappearance from
> the
> > > fossil
> > > > record the dinosaurs were already dying out.
> This blatantly 
> > > > contradicts what another paleontologist
> > > in a
> > > > different episode of the same series says,
> > > claiming
> > > > they were thriving. I could be mistaken, but
> in
> > > "When
> > > > Dinosaurs Roamed America" I thought something
> was 
> > mentioned that in 
> > > > the time leading right up to
> > > their
> > > > extinction that there was a relatively low
> number
> > > of
> > > > species yet in an issue of National Geographic
> > > from
> > > > 1999 on Sue, it explains that the dinosaurs
> were rapidly 
> > > > diversifying. How can their be such
> > > blatant
> > > > contradictions on the matter?
> > > 
> > > To a large degree, it depends on what time scale
> and 
> > taxonomic level 
> > > you are looking at. Most of the traditional work
> supporting "no 
> > > evidence for decline" has been looking at the
> species or 
> > family level 
> > > within the Hell Creek or the Lance, and there is
> no sign of decline 
> > > that way.
> > > 
> > 
> > Right, but by that point 'lambeosaurines',
> 'centrosaurines', 
> > 'nodosaurs' and possibly sauropods had all gone
> extinct in N. 
> > Am. Arguably, all but sauropods went extinct
> before even 
> > Alamosaurus-times (~69Ma pre-Lance/Hell Creek)..
> So there's a 
> > very strong argument for declining diversity
> before the K-T 
> > boundary... at some point in the Edmontonian, very
> probably 
> > associated with onset of the final regression of
> the WIS.
> > 
> > However, yes, within the final million years or so
> covered by 
> > the Lance and Hell Creek, you don't see any taxa
> go extinct 
> > (until the boundary of course).
> > Historically, you could argue that we see a small 
> > diversification amongst Chasmosaurines; instead of
> just one 
> > species (as was the status quo throughout the N.
> Am Late K), 
> > there are two. But this is false since both
> Torosaurus and 
> > Triceratops are present in the Alamosaurus fauna,
> so this 
> > diversification presumably happened about the same
> time as 
> > centrosaurines and lambeosaurines disappear.
> Hmmm....... now 
> > that's interesting....
> > 
> > 
> > 
> > > Most of the traditional work supporting a
> decline looked at the 
> > > subfamily level over the last 15-20 million
> years or so.
> > > 
> > > The recent work by Fastovsky (supporting a
> possible increase, or at 
> > > least stable) looked at the species level over
> the whole of the 
> > > Cretaceous.
> > > 
> > 
> > I don't really agree with the oversplitting of
> alot of the 
> > North American taxa (especially ornithischians);
> it gives a 
> > very false idea of dinosaurian diversity.
> > For example, it is extremely difficult (if not
> > impossible) to tell one lambeosaurine from another
> 
> > postcranially, even size- wise there isn't huge
> variation, 
> > yet the likes of Lambeosaurus, Corythosaurus,
> Parasaurolophus 
> > etc are afforded genus-level distinction.
> Substitute any of 
> > the ornithischian subfamilies and the result is
> similar.
> > 
> > Contrast this with my old buddy Iguanodon, which
> shows as 
> > much variation between the contemporaneous
> I.bernissartensis 
> > and I.atherfieldensis as is seen between the
> Hadrosaurinae 
> > and Lambeosaurinae (noone ever suggested
> hadrosaurs and 
> > lambeosaurs were male-female, and they shouldn't
> for Iggy 
> > either). Do we really see endless diversity of
> species/genera 
> > in North America in the late K, or is it just a
> single 
> > representative of any given 'group', at any one
> time? 
> > 
> > 
> > > Too bad no one's looked at Campano-Maastrichtian
> 
> > dinosaurian diversity 
> > > with an eye towards phylogeny... Oh, wait.
> Right.  See you at Mesa, 
> > > people! :-)
> > 
> > I'll be very interested to see what you have to
> say Tom! 
> > 
> > Denver.
> > 
> > 
> > 
> > 
> > > 
> > >           Thomas R. Holtz, Jr.
> > >           Vertebrate Paleontologist
> > > Department of Geology             Director, Earth, Life &
> Time
> > > Program
> > > University of Maryland            College Park Scholars
> > >   Mailing Address:
> > >           Building 237, Room 1117
> > >           College Park, MD  20742
> > > 
> > > http://www.geol.umd.edu/~tholtz/
> > > http://www.geol.umd.edu/~jmerck/eltsite
> > > Phone:    301-405-4084    Email:  tholtz@geol.umd.edu
> > > Fax (Geol):  301-314-9661 Fax (CPS-ELT):
> > > 301-405-0796
> > > 
> 
=== message truncated ===



        
        
                
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