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Re: _T. rex_ strikes ( was Ceratopsian frills)



Thomas R. Holtz, Jr. wrote:

> Steve Throop wrote:
> 
> >In the Jurassic, I understand there were a lot of sauropods and
> >stegosaurs, long-necked animals who could have eaten tree leaves and
> >used their tails to strike predators.  The stegosaurs and most sauropods
> >disappeared about the time tyrannosaurs appeared.
> 
> Well, the stegosaurs survived for 30 or so million more years into the
> Cretaceous, and sauropods survived until the end of the Cretaceous in many
> parts of the world.

I once hoped I might pose as an expert if only I could understand
cladistics.  Then someone on the list dashed my ambition by pointing out
that chronology is also important. :)

Here's Robert Bakker: "Sudden extinction interrupted the evolution of
dinosaur armor at the end of the Jurassic when the true stegosaurs died
out totally or at least became very rare."

Suppose a farmer gets a new dog to help control rats.  No predator will
be able to exterminate them all, but reduced numbers will be evidence of
successful hunting.  If in the future the farm's vermin are different
from the original rats, that, too, could show that the new dog is a
better hunter than the other dogs and cats.

Stegosaurs seemed pretty invulnerable with their strong, exceptionally
flexible, spiked tails and their ability to turn quickly.  If they
became scarce, couldn't this mean there were now predators who could
disable them before they could react?

Nodosaurs had quicker tails, extensive armor, and spikes along the
sides, particularly at the shoulders.  This sounds consistent with
defense against impact hunters too quick for stegosaurs.

Recently, the list discussed the overturned fossil of a massive, stable,
armored dinosaur.  Couldn't this have been like the case of a heavyset
catcher bowled over by a baserunner coming home feet-first?  If it were
possible, wouldn't this be the most effective way to attack?

> Tyrannosaurid diversity, as currently known, is highest where sauropods are
> absent.  Although one could argue a cause and effect, you'd have to explain
> what Gorgosaurus and Albertosaurus and Daspletosaurus were feeding on after
> they offed the yet-to-be-found Judithian and Edmontonian sauropods...
> 
> (The more common explanation is that these tyrannosaurids were eating
> ornithischians, which were embarrasingly common at the same time and place).

We seem to be thinking along the same lines.  I can imagine going after
a duckbill like a wolf, but impact seems like the best way to take down
an ankylosaur or a ceratops.  If prey included various kinds of tough
nuts to crack, wouldn't tyrannosaurs have developed into various species
of tough nutcrackers?

> However, some tyrannosaurids lived in the same time and place as sauropods.
> Early tyrannosauroids, like Siamotyrannus, occur with sauropods, as do later
> Asian forms (Tyrannosaurus bataar).  The southern end of T. rex's range
> includes localities from which the titanosaurid Alamosaurus are known, but
> it is not established if the latter ever made it into the nothern part of
> the range.

Ranges, too.  Besides cladistics and chronology, I wish I knew more
about ranges.

Rats have lots of very able enemies, but they aren't extinct even where
predators are most abundant.

> >I understand most surviving sauropod species were related to
> >_Brachiosaurus_, whose neck was a startling 6 meters off the ground.
> 
> Indeed.  One of the middle-range necks of a sauropod: it's longer than in
> camarasaurids or dicraeosaurids, but nothing like the really long necked
> forms: euhelopodids and diplodocids!

I don't think it would do much good to bump a sauropod's neck up near
the head even if a predator could do it.  By "6 meters off the ground,"
I meant the base of the neck.  

My picture of a camarasaurid shows a height of 5 meters.  I doubt a
tyrannosaur could slam something that high.  According to my pictures,
the other three had necks about 2.5 meters off the ground - low enough
to trip _T rex_.  

Thanks for your remarks.  Information is the sincerest form of flattery!

- Stephen Throop