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Re: New dinosaur diversity articles



Btw, with regard to Gondwana, and Europe,
nontitanosaurid sauropods may have vanished by the
Maastrichtian. Spinosaurs are not known after the
Cenomanian, and stegosaurs were long gone. 
 Even among theropods, diversity apparently declined
somewhat. As Holtz wrote, there were no intermediate
sized predators in the tyrannosaur environments, and
tyrannosaurs were the sole large predators, in
contrast to the greater large theropod variety in the
Morrison. AFAIK, there were no giant raptors anywhere
in the Maastrichtian.
--- Tim Donovan <uwrk2@yahoo.com> wrote:

> 
> > The data do not
> > suggest that dinosaurs were decreasing in richness
> > leading to extinction
> > during the last 10 m.y. of the Cretaceous.
> 
>   Lambeosaurs appear far less diverse in North
> America
> by the early Maastrichtian. Hypacrosaurus is the
> only
> post Campanian NA lambeosaur genus known AFAIK. *
> Centrosaurines were also down to one genus by
> then-Pachyrhinosaurus-and were totally gone by the
> late Maastrichtian. Saurolophines had also vanished
> by
> then. The recent Ankylosaurus paper claimed that
> ankylosaurs disappeared before the end. That may not
> have been true of Ankylosaurus, since  specimens are
> stratigraphically high, and one occurs right below
> the
> K-T according to Wroblewski's data. Edmontonia,
> however, may have disappeared before the end.
> 
> 
> 
> > Refinement of the dating of
> > dinosaur fossils, rather than the collection of
> more
> > dinosaurs, is the best
> > way to resolve globally the rate of the
> > Cretaceous-Tertiary dinosaur
> > extinction.
> 
>   IMO it is very important to determine which unit
> is
> younger, the Nemegt or the Tsagayan. If Godefroit is
> right and the Tsagayan is younger i.e. late
> Maastrichtian, that would certainly argue against a
> decline in diversity. If the Nemegt is younger, that
> would suggest hadrosaur diversity declined in Asia
> as
> well as in North America.
>  
> * Hypacrosaurus may have persisted into Hell Creek
> time but its putative remains are stratigraphically
> low and rare, suggesting that it was on the verge of
> disappearing. AFAIK lambeosaur remains are not known
> from the Scollard, which is equivalent to the upper
> Hell Creek, and representative of a more inland
> environment favored by lambeosaurs.
> 
> 
> 
>               
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