[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Saber-toothed cats and big theropods (was Re: Various minor subjects)



David Marjanovic wrote:

<Of course a mammoth is "too big and powerful" for *ONE* saber-toothed
cat.>

  Naw, there were small mammoths. Yea, even back then, when one could
suggest *Homotherium* and some eastern Eurasian mini-trunk could go at
it. But that's not today. Today we have a different set up. Elephant =
really, really, really big ground animal; lion = a lot smaller, more
easily squishable.

<What about a pack? (I don't know about any evidence for or against
packing behavior in saber-toothed cats, but a pack of _Allosaurus_ or
_Giganotosaurus_ should have been capable of killing just about
anything.) As mentioned before onlist, a pack of lions can kill an
adult elephant (but rarely does so -- after all, lions don't have saber
teeth).>

  Not the reason, in my estimation. It's because of the size disparity.
And before we get into useless speculating about the ability of a
sabre- or dirktooth cat being able to take down mammoths, using lions
for a point of reference no doubt, you gotta take in stock that one of
the _big_ reasons lions don't make a habit out of eating elephants is
because they are so much _smaller_ than the potential prey, and when an
eleven ton animal doesn't want to be eaten and you have some palty 3-4
300lb critters coming after it, the disparity is negligible. When one
considers the prey to have the strength to _pull up trees_, then lions
take heed, always have. It is not the norm for a reason, and
extrapolating a _very_ rare occurence as allowing the possibility for
an entirely different animal and biomass ratio and equippage, then
you're getting far afield.

<I suspect evolutionary constraints: Saber teeth are canines, and
saber-toothed cats apparently still chewed -- they retained the
carnassials.>

  Carnassials are not chewing teeth, they are not something retained.
They are derived shearing mechanisms for which are the hallmark of the
carnivores. Cat's can't chew, and for that matter, neither can dogs.
They slice their food in strips or small chunks and _swallow_ the bits.
They swallow bits we _do_ have to chew to swallow. Cats, relative to
dogs, are hypercarnivores: they are adapted to eat meat, and they can
eat very little else, becuase they lack to ability to process any other
form of food outside of flesh.

<Only the canines had the potential to be lengthened.>

  Some cats and dogs show a trend in the length and height of the
carnassials or premolars, and cats for one are diagnosed by the
carnassial length, as well as the incisor length.

<On the other side, saber teeth are enormously long compared to skull
size. Theropods had only saber teeth, so to say, didn't chew, and the
individual teeth were relatively smaller. Theropod teeth hardly had
identities, in contrast to a mammal where you can say that a saber
tooth is homologous to my canine and not the tooth in front or behind
of the canine, so all looked more or less the same in size and shape.> 

  Theropods have the typical reptilian equippage of homodont dentition:
that is, all teeth are of the same morphology, implantation, etc. It is
the norm. It is rare to see a heterodont reptile, but its occuring more
and more frequently that we find a group of them in some select
branches as bearing non blade-like teeth, such as the chimaerasuchs,
etc., in the crocodylians, or herbivorous dinosaurs, and also in some
maniraptoriform theropods (D-shaped premax teeth, shifted distal
carinae, etc.) where the dentition depends on position or use. Even so,
hadrosaurs are still homodont. But they _do_ have identities, and you
can tell the position of a troodont tooth, to a great accuracy, for the
majority of forms, because the dentition in this group is rather
generalized. *Byronosaurus*, for instance, is the odd man out.

  But to equate this homodont, ziphodont dentition in theropods as
regulatory is to ignore the complexity of the ziphodont teeth: take
carcharodontosaurine (mesiodistal wrinkles and very narrow blades
expanded), tyrannosaurine (incrassate, lateral bending resistance),
troodont (multiple sub-phyllodont crowns with distinct blood grooves
[for gripping fibers] on the distal carina).... Sauropods had stranger
teeth, but this is off the point. Something neglected is classifying
dinosaur teeth into their functional categories, though this was done
for some selecet theropod groups, and a few sauropod groups, the full
distinction and variety (especially in ornithischians) has not been
realized, as I see it.

  Have ye all a wonderful holiday, I get to stay at home and play with
the tree,

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

__________________________________________________
Do You Yahoo!?
Yahoo! Shopping - Thousands of Stores. Millions of Products.
http://shopping.yahoo.com/