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Oviraptorids as Parrots?
Y'know, I was kinda enjoying the sauropod biomechanics topic since it seems
to have generated the most proactive discussion yet in this forum's history, to
my estimate, with such esteemed commentaries from practical research on the
parts of Kent, GSP, and Scott. So when another biomech discussion rears its
"ugly" head, one must focus once again. Or at least, myself.
... my pretties ...
There are a good deal of similarities between the construction of the
oviraptorid skull and that of parrots. This wasn't obvious from the view point
of Granger when he discovered the holotype of *Oviraptor philoceratops* in the
sandstone below the cliffs of Bayan Zag. It wasn't obvious when Osborn had it
partially prepared and sent a note to _Natural History_ on the discoveries led
by the crew of Roy C. Andrews into central Asia in 1922 and 1923, and he called
it "Fenestrosaurus" as he seemed to note the light and airy structure of the
skull with its large fenestrae. Afterward, Osborn would simply note its
proximity to a nest of eggs, saw it was edentulous, and christened the animal
for all posterity *Oviraptor philoceratops*, the egg thief, fond of
ceratopsians. Most important of Osborn's features was a bony prong sticking
down from inside the medial jaw, perfectly suited to puncturing eggs.
New research on the jaw anatomy would have to wait another 50 years, when
Barsbold began his research on fossils found in the 60's and 70's during the
occupation of Mongolia by Russia. He performed a short-form analysis on the
skull of one specimen and generalized form of an oviraptorid in 1977, and found
that the jaws seemed perfectly designed for the crushing of objects in the
mouth; Barsbold would claim, however, that the preferred food would have been
shelled animals, bivalves (mollusks) and ostracods (clam-imitating
crustaceans), because the jaws seemed overly built for such delicate things as
eggs. Indeed, two prongs in the top of the jaw, inset from the sides and formed
from the maxillary bones where they fold beneath the vomer (which subsequent
researchers would continue to refer to as "teeth"). The problem, as shown even
later by David Smith, was that what Osborn had pointed to as prongs in the
holotype of *O. philoceratops* were in fact ectopterygoids. Be it so, Osborn
would be borne out for identifying at least an animal suited to crushing
shelled food. Barbsold would later add to the collection of oviraptorids (and
the name, Oviraptoridae) by describing new species of oviraptorid, including
"Ingenia" (preoccupied) and *Conchoraptor*. The latter taxon would be a nearly
double entendre to Barsbold's hypothesis, perhaps not intended, for these
"conch"-eaters. The word used, konkge, means "seashell", deriving from a Latin
word of the same meaning. Prescient? Who knows.
In the early 90's, however, the old myth of the egg-terrorizing oviraptor
would come face to face with ugly truth. Dong and Currie would publish on a
find from Bayan Mandahu in Inner Mongolia, China, of a partial oviraptorid on
top of a collection of paired eggs; the poster of the arm was wrapped backward
around a folded leg atop what appeared to be undisturbed eggs, and prompted
them to propose the find of the first known oviraptorid nest. Meanwhile, Norell
and associates uncovered a bevy of fossils from Ukhaa Tolgod, hundreds of miles
west of Bayan Zag but largely the same age, which would allow them to argue the
eggs it was caught stealing were its own. The primary find was that of a
delicate embryo of an oviraptorid on a half-shell, the same shell Granger had
found nearby a clutching oviraptorid, and which Dong and Currie found beneath a
partial skeleton. This would catalyze them to nickname a specimen later
referred to *Citipati* as "Big Momma". The eggs had come home, and with it a
challenge to Osborn's hypothesis, and perhaps a revival of Barsbold's.
Along with the embryo, two tiny skulls Mickey previously mentioned of "baby"
*Byronosaurus* (originally thought to be dromaeosaurids before an adult skull
of *Byrosaurus* was recovered) were associated, and these were considered to
pertain to food brought by the nesting parent to feed soon-to-hatch babies. It
is also possible these animals were present to feed on the unhatched
oviraptorids, as it is also possible that a mother troodontid have brought
them. However, this is all speculative and associative.
Barsbold attempted to glean the diet direct from the horse's -- err,
_oviraptorid's_ -- mouth, but several qualities had not been quantified and new
studies would tell us what the possible abilities of the snout would be. One
major issue that thwarts published data from comaparing the skulls is that we
do not yet know the forces the skull could withstand; work such as Rayfield and
others are performing on skull after skull has not reached this group yet.
However, following Barsbold, we know that oviraptorids skulls, like turtles but
unlike parrots, tend to the akinetic, without mobile snouts or palatal
elements. Some features are similar: a ventrally enlarged, deflected palatal
process and pterygoideus anchor, as in crocodylians; the snout is greatly
enlarged relative to skull size, and the skull is hypershortened (extremely
brevirostrine, in croc-terms); the skull retains large open spaces in the skull
and the cranial framework tends to shape as a box, rather than the psittacine
typically avian cranium, or the "plank-like", broad snouts of living
crocodylids and alligatorids, built to distribute forces acting on one side
across the snout, and from the front to the back, thus minimalizing stresses
throughout the skull and limiting torsion.
Sam Koning mentions some behaviors of parrots in frugivorous feeding, that
parrots will use their beak to cut open a fruit's husk to get at the pulp.
However, while it is possible the oviraptorid snout is similar, we should
consider than parrots are a bit odd when it comes to birds, even though that
feed on fruits such as toucans: parrots, for their size, have the largest heads
of almost any bird, and this seems to serve as a functional "third leg" (no
jokes please!) for birds that clambor around thin branches and twigs for
inaccessible fruits otyher birds cannot get, or for getting those difficult
dangling fruits by suspending themselves and using the head to gain leverage.
Parrot feeding is fascinating to watch, and aided by that magnificent rostrum,
of which the prokinetic hinge is important, while one foot is often raised to
rotate the fruit for easy manipulation and processing. This is an exceptional
adaptation, and it would seem that relatively small headed oviraptorids are
similar, but they do in fact lack that typical parrot-like rostrum, and it is
unlikely that fruits were their preferred foods, as these do not tend to be
ample foods on the ground, since parrots (for most of the African ones at
least) are cliff or canopy dwellers who feed in the regions of fruit abundance
-- in trees.
Yet, even so, most parrots feed by placing the hard food between platforms
formed from keratin of the jaws and crushing the nut or hard fruit until they
can release the germ or pulp. This behavior is performed by various other
durophagous animals, suited to crushing with their jaws, from aardwolves to
various (but by no means all) turtles [especially the ocean-going variety] to
walruses (though I admit in the latter it has not been so observed as much as
inferred given that walruses suck in shellfood, then spit the undigested shell
back out). To look at the commonality among durophagous animals is the best way
to observe the possible use of the jaws in the similarly adapted oviraptorids.
This is the focus of most of my research, so you will excuse me for being brief
in my conclusions. What I have described above has been largely historical and
drawing in the major modern analogues that I would encourage anyone curious
about the subject to consider.
Especially important, I think, for researchers to consider if they wish to
elaborate on this is to investigate various animals suited to eating
hard-shelled food and do it successfully THROUGH the shell (that's right, the
occassional lucky lion or baboon who kills a turtle doesn't count, nor I think
do those vultures that like to drop them from on high or sea otters to crack
shellfood against stones).
Jaime A. Headden
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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