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Re: Tyrannotitan, new carcharodontosaurid from Argentina



Tim Donovan (uwrk2@yahoo.com) wrote:

<I think you meant leopards are vulnerable to lions but remain key predators.>

  No, actually I meant what I had written. Leopards can and do kill lions. It's
not common, but it happens. Even more common is "predation" on lion cubs and
sometimes adults from warthogs, but this is pulling the niche to its limits.
"Top predator" does not mean you're immune to other predators in the region,
just that they will tend not to kill the "top" animal without opportunity and
necessity.

<Why else would an elongated snout and jaws evolve? If spinosaurs were more
massive and powerful than carcharodontosaurs, and piscivory seems questionable,
could they have been sauropod hunters, using their long jaws to reach the necks
of titanosaurs or rebbachisaurs? Could their manual claws have been offensive
instead of defensive weapons, used to rip open a sauropod's throat or sides?>

  First, assess all animals with elongated snouts and jaws before concluding
why they were present. Then determine commonalities of feeding style, habitat,
nature of predation, etc. For example, long-snouted animals also consist of
echidnas, kiwis, herons, tamanduas, gharials, *Pterodaustro*, etc. Feeding
styles and likely foodstuffs as well as environments vary widely among these,
from near-shore and fluvial, to forest floor, to bayou, to arboreal. Only two
of these were apparently maximal fish eaters, and even then herons are
opportunists and not strictly piscivores.

  Second, carcass-scrounging HAS been suggested as the reason for long snouts
in, say, jackals, which are almost nearly first or second to a carcass (not
claimed by the killer). They are also the last to clean up, usually, and use
their snouts to gain access to crevices. I see this as a possible adaptation
for long snouts, but not the particulars of the teeth (not suited for shearing
meat in spinosaurines, though possible in baryonychines) nor the "terminal
rosette" where the expanded symphyseal region negates the idea that the snout
is "narrowed" for crevice access; only *Angaturama* (? = *Irritator*) has an
unexpanded symphyseal region of the jaw in spinosaurids. Spinosaur necks seem
adapted to cantilevering large loads, likely from the jaws, and the arms are
massive, equipped with "railroad spikes" that have been likened to meat-hooks.
This was dramatically described in possible use when, in the movie _Jurassic
Park III_ the spinosaur rolled the fuselage of the downed plane (why, I have no
idea) but it is easy enough to tear into a carcass or large prey and grapple
with it.

<The variety of suitable prey for giant predators in the Baharije environment
doesn't appear to have been great. What else was there for a big predator
besides sauropods? Stomatosuchus? Ouranosaurus wasn't present in that
environmnt.>

  More than two species of sauropod, crocs like *Stromerosuchus*, smaller
undescribed theropods, several large-sized theropods, the 3m lungfish
*Mawsonia*, the "legged" snake *Simoliophis*, elasmobranchs like *Carcharoides*
and *Sechmetia*, etc. Possibly more than enough to sustain possible varied
theropod diets. Rarities of some animals may indicate transport from upland,
non-paralic environments, though water energy is low in such regions.

<Carcharodontosaurs are usually thought of as sauropod hunters. If spinosaurs
were more powerful, maybe they took on the largest sauropods, like Paralititan,
and became extinct with such big prey by the Turonian.>

  Supposedly because of Paul's "slice and dash" hunting technique. This was
posited from narrow skulls and U-shaped symphyseal regions -- which spinosaurs
share. The problem is is that Rayfield and Molnar, as well as Mazetta and
others, have indicated a likely more "hatchet-headed" method of ramming the
upper cranium onto the flank and then letting inertia tear chucks out. This
gives a BIG gash or a large chunk for a given amount of energy and likely very
short time. Would this have been employed while the prey was living? Not that
many animals today, anyway, feed in such a manner while prey lives, though I've
seen footage of lions begin to eat an exhausted trapped water buffalo....
 
  Cheers,

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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