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Re: Oviraptorids as Parrots?



Hi all,
There are some articles that deal with bite force in feeding in birds,
which might be interesting in the view of this discussion. They are:
Sander W. S. Gussekloo and Ron G. Bout Cranial kinesis in palaeognathous birds
J. Exp. Biol. 2005 208: 3409-3419.
Sander W. S. Gussekloo and Ron G. Bout The kinematics of feeding and
drinking in palaeognathous birds in relation to cranial morphology
J. Exp. Biol. 2005 208: 3395-3407.
M. A. A. van der Meij and R. G. Bout Scaling of jaw muscle size and
maximal bite force in finches
J. Exp. Biol. 2004 207: 2745-2753.
Furthermore, it is hypothesized (Zweers et al) that the most primitive
form of feeding in birds was a so-called 'catch-and-throw' method, in
which a food item is grabbed and thrown into the air to be
subsequently swallowed.  Maybe a similar method existed in advanced
theropods such as oviraptors?

all the best, Hanneke

----------------------------
Hanneke Meijer
www.PalArch.nl


On 2/2/06, Jaime A. Headden <qilongia@yahoo.com> wrote:
> 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).
>
> Cheers,
>
> Jaime A. Headden
>
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
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