RE: Bakker's Brontosaurus and Late Cretaceous populations

[Ken.Carpenter@dmns.org]

> (noone ever suggested hadrosaurs and 
> lambeosaurs were male-female,

Nopcsa suggested this in 1929

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
> > 
> > 
> 
> 
> 
>               
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