Therizinosaur Feeding

["Jaime A. Headden" <qilongia@yahoo.com>]

Recent posts on the diets of therizinosauroids
(segnosaurs) make me wonder why Norman wrote that
passage in his _Encyclopedia_ on apparent piscivory.
There is no evidence for such a diet except terrain
and the hypothesized webbed feet based on the elongate
claws and broad feet.

  However, there are problems.

  PISCIVORY

  Segnosaurs lack the teeth to make effective
fish-eaters, and the so-called webbed feet were way
too short to be webbed; basal birds, such as
hesperornithiforms, have leaf-shaped teeth, like
segnosaurs, which may have been used in the seizing of
fish.(see Norman, 1983; Feduccia, 1996.)

  FORMICIVORY

  I like this one at least for the idea of
anteater-analogies in the Cretaceous. Modern
formicivores have a severe reduction in tooth count
and very slender, rounded snouts, which segnosaurs
have the reverse of. The major evidence in favor of
this is *Therizinosaurus'* long claws resemble
superficially those of diggers, yet they are not
dorsoventrally (top-to-bottom) flattened, but
laterally (side-to-side), as in nearly all true
carnivores. (see Norman, 1983; Lambert, 1996.)

  CARNIVORY

  Long, trenchant claws in segnosaurs are used as
evidence for thagomizers, devices used to kill. The
teeth, however, are small and leaf-shapped, which very
few carnivores possess (an exception may be small
crocs and such, plus basal birds, but this second
group can also be used to support a piscivorous diet,
and also troodontids -- animals for which a variety of
diets have also been proposed). (see Barsbold and
Osmolska, 1990; Lambert, 1996; Barsbold and Maryanska,
1990; Maryanska, 1997.)

  HERBIVORY

  A variety of herbivorous sub-categories (such as
folivory [leaves], frugivory [fruits], and granivory
[grains]) have specializations that segnosaurs lack,
including specialized teeth or limbs for the
processing or aquizition of such. Generally,
herbivores lack teeth at the front or in all the jaws,
as in ornithschians and birds, and widely expanded
guts, to process the tough fibers, also as in both;
segnosaurs have both. This is by far the best
explained diet proposed for segnosaurs, supported by
most of the examiners of these animals. (see Barsbold
and Osmolska, 1990; Maryanska, 1997; Barsbold and
Maryanksa, 1990; etc..)

  The full references for these citations can be found
on my site's ref page:

  http://members.tripod.com/~Qilong/refs.html

  Questions? Something I missed, something I got
wrong?

===
Jaime A. Headden

"May I lure us, ere the mote ends us?"

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