Osborn Was Right

I am not going to go into too much detail with this post.

Following recent discussion on the applicability of blogs as distributors of information, I am going to try a tactic whereby I outline an argument I’ve been cultivating and testing for nearly two decades. For me, this is my only “real” pet project, my personal hypothesis. What follows is an outline with a small historical thesis, so it’s being told as a research propsal. This is something I do intend to publish on — consider this a long-form abstract.

In it, I argue that Oviraptor philoceratops, and indeed most oviraptorids, are adapted, specialized carnivores. Recent work has supported the conclusion that they were instead herbivores and/or omnivores, from the work of Dr. Lindsay Zanno and colleagues; this work provides “outs” in that specialization is often hard to find in the fossil record, and especially when diet among extant animals can be extremely variable. Moreover, despite several seeming “herbivorous” adaptations, such as lack of teeth, this should not itself result in herbivory: oviraptorosaurs lack the expanded, wide gut of an herbivore, retaining predatory features of the manus and even pes suggesting they engaged in live prey handling. There was, it seems, no direct evidence for herbivory in oviraptorids.

In 1924, Henry Fairfield Osborn supplied the world with this bizarre animal and it’s monicker — the egg thief, fond as it was of the eggs of Protoceratops andrewsi – arguing that it was, in fact, a consumer of eggs. In that work, he opined that the association of the first oviraptorid described ever to a nest it was assumed to belong to Protoceratops andrewsi, and the seeming absence of teeth and a “ventral prong” on the roof of the mouth, should have clearly determined it was an eater of eggs, a consumer of shells, and depredator on the future lives of the Gobi’s “sheep.”

AMNH 6517, holotype and only known skeletal specimen of Oviraptor philoceratops Osborn, 1924. From Norell, Gaffney & Dingus, 1992.

No matter that Osborn put forward Velociraptor mongoliensis; Tarbosaurus bataar would not be discovered for 30 years: The Gobi Desert had its first villain. Depicted in countless art books and in some recent film as a dastardly destroyer of nests, Oviraptor was that most insidious of creeps: the sneak. Blink, and you could miss him.

In the 1990s, the American Museum of Natural History returned to the Gobi Desert, on the heels of the Russians (who’d trained the Mongolians in paleontology, and helped them grow into the force they are today), the Polish (headed by some of the only prominent women paleontologists in the entire world), and the Chinese (who traded Mongolia with the Russians before Mongolian independance), who were also joined by the Canadians, who also later partnered with the Japanese in current expeditions. The Americans, who were there first when China had power, returned, and among their first discoveries located nests and nests of dinosaurs … only this time without a ceratopsian on top. Names like “Big Momma” and “Big Auntie” are now useful monickers. James Gurney used the name “Ovinutrix” as an effective replacement for the name “Oviraptor,” seeing as how it was not so much the predator as the nurse, the mother. Osborn’s specimen, as discovered by Walter Granger, was a delicate flower.

[I personally think “Ovinutrix gurneyi” is a fine name for a new oviraptorid, and no this is not the name I would use for MPC-D 100/42.]

It wasn’t the only word on the subject, though. In the 1970s and continuing into the 1980s, Mongolia’s own Barsbold Rinchen offered a contrary opinion on the diet of oviraptorids, owing as it did to complete skulls the Polish and Mongolians has uncovered, later bearing the names “Ingenia” yanshini, or Rinchenia mongoliensis, or Conchoraptor gracilis. These make up the classic Oviraptoriteers, with Oviraptor philoceratops as D’Artangan. They are the basis of mechanical analysis Barsbold used to propose an alternate food source, molluscs. Rather than eggs, they seem “overbuilt” for that, and would rather have been suited to crushing clamshell.

I have been somewhat skeptical on these conclusions on a variety of grounds, and though my education has limited my resources, I had spent that time developing work on determining what, exactly, it was that oviraptorids ate. I looked at development of edentulousness in terrestrial and marine tetrapods, development of durophagy, and specifically development of egg-eating. As it turns out, some factors do not align themselves well with an herbivorous or even molluscivorous oviraptorid, or at least for the majority or the largest ones. Several features of the skulls of oviraptorids are of supreme importance to this debate:

1. The presence of a ventral projection from each maxilla to the midline of the skull;
2. Absence of a broad and mostly flat platform expanding across the jaw or along it;
3. Absence of a broad platform on the mandible, or indeed any broad feature of the mandibular margin.

I’ve investigated the myology of the skull, focusing on the jaw adductors and discriminating jaw protractors and retractors to attempt to resolve jaw attitude during the bite stroke. I’ve also looked at and surveyed the way extant durophages and ovophages eat. When it comes to ovophages, however, I am sadly disappointed in that virtually all extreme or exclusive ovophages are snakes, and of these, oral processing is limited; it is present in some species of Oligodon (kukri snakes), and the novae dental morphology is interesting to examine, but in other ovophagous snakes it is quite distinct, and occurs almost exclusively post-orally. Durophages suited to consuming hard-shelled prey also focus on broadened dentition supported by labiolingually expanded dental platforms, and so lizards like blue-tongued skinks (or shinglebacks) Tiliqua sp., the caiman lizard Dracaena sp., the Varanus species exanthematicus or niloticus/ornatus, or the globidensine mosasauroids Globidens sp. are important in noting that consumption of hard-shelled prey often occurs on one side of the jaw at a time, rather than through both. This is possible due to weak kinesis of the skulls in all of these taxa, allowing each side to distort relevant to the stresses of the side applying pressure. It is a model that applies for Globidens, a pet project of mine as well but in smaller doses. But it suggests to me that oviraptorids are doing something different.

Indeed, a major component of the study was to determine what exclusive egg-eaters were, if any, and how they got that way. That question has a plausible answer, and it links us back to the American Museum’s second suite of expeditions to Mongolia. This was largely built on the discovery of perinate troodontid skulls in a nest of Citipati osmolskae. Although many possible explanations exist, including random association or predation on the oviraptorid eggs by a troodontid, the first hypothesis might be the most sound: oviraptorid predation on troodontids. There are carnivores, then there are carno-vores: predation upon carnivores, specifically. Likely, though, it was opportune feeding. One of the big complaints about egg-eating in oviraptorids is seasonality, and energetics. Snakes manage this by being cold-blooded, but also where Dasypeltis sp. and similar egg-eaters have slower metabolisms than less picky consumers. They make efficient use of a particularly picky diet. Alan de Quieroz and Javier Rodríguez-Robles found that predation of egg-laying species neatly bracketed predation on eggs of that species, regardless of whether the predator was a consumer of birds, or of squamates; they would prefer the eggs of the species they otherwise interact with. This has the added import that if an animal were a consumer of eggs, as a dinosaur, it might favor consumption of that egg layer first. And this pulls us back to oviraptorids as carnivores.

It is further important to note that I am fairly well-aware of the problem of exclusive egg-consumption related to potential seasonality of egg sources. First, I must be able to determine availability of eggs as a resource relative to time, and then the energetic value of the eggs in question (which would likely use bird eggs such as those of ostrich or other large-egg layers as a model, and go down from there  — and try to exclude domestic fowl, for I hope obvious reasons).

How they might have eaten also became a part of the research. For one, they cannot necessarily bite on just one side of the jaw: The hemimandibles are fixed relative to one another, and while they aren’t fused there is a tight interdigitation which keeps them in relative position. The jaw joint has brought parallels with birds in some fashion, but especially turtles and dicynodonts. This meant more work exploring diet in those groups, and jaw mechanics. It is likely that the jaw could precisely occlude on one side or the other, depending on the ability to shift articulation of the jaws; however, a distinct and prominent intercotylar ridge of the articular seemingly prevents this, as well as producing distinct distal quadrate condyles, and thus that the jaw was likely enforced in articulation without much “yaw” in the orientation. And the real hurdle.

Wishing as I did the energy to pursue things as I did when I first started on this project so long ago, and the knowledge of anatomy I now possess back then, I likely would have had substantive work already prepared. See, what I wanted then was to test my model mechanically. There were three ways I could do this: I could apply Finite Element Analysis, but this requires the software and the model, for which I would have preferred a scanned three-dimensional skull of an actual oviraptorid; I could use simple beam analysis, but this doesn’t help when testing different food stuffs; and I could use box-frame analysis, but that’s simply a larger version of beam analysis, and when you have a working group that is largely considered akinetic, pointless. I could also construct a mechanical frame in person, and fashion it out of a resin or steel duplicate of an oviraptorid skull, and have it do all the biting for me. This one is a fun one, and a practical one which allows me to do many other things which might not be entirely “scientific,” but still quite enjoyable. Like Anne Schulp’s Carinodens model, I could use it and a pressure gauge to determine the force required under a variety of materials and derive potential efficiency. Being “overbuilt” is not a problem, actually, as it permits me to provide myself an upper limit: it is obvious that the animal might be able to overcompensate its bite, especially if it retains the bite force from less soft materials. The difficulty is in having “underbuilt” jaws for a particular food: If the jaws cannot process bone, or any reasonable thickness of snail or clamshell, then there is no reason I should expect it to feed on those animals. Building the thing would have to com first, then I could feed it clams, oysters, and even eggs. The cost is beyond me at the moment, though.

But what I really want is an FEA analysis and the grounding to work on real oviraptorid skulls, to refine muscle placement and morphology. This led to figuring out how the soft-tissue of the skull might work out, and that’s why you’ve seen occasional images like this:No, nothing's wrong with his head. Why'd you ask?or this:

These represent stages along the way to reconstructing a skull model which becomes the basis of further tests that affirm my premise:

Oviraptorids ate eggs, likely as a massive component of their diet, and because of this Osborn was right — on at least that premise, and the form of the name.

Part of the research has developed into reconstruction of rhamphotheca, taphonomy of tissue loss and association of cranial tissues from only bone. I’ve focused on effects around the oral margin, but have not ignored other elements of the skull. So, I’ve attempted to expand my comprehensiveness on knowledge of cranial and jaw morphology and diet in archosaurs, and indeed tetrapods, but I’m not smart enough to simply know this stuff. I lack the library to crank this stuff out or the laboratory to do practical analysis so easily. And I lack the travel to get to the places where these skulls, these oh so valuable skulls are located, so that I may examine them … at length. (I wouldn’t be wasting my time on just them, however, as these places also have specimens with actual teeth I may also desire to examine, down to the enamel microstructure and arrays of denticles.) So … it takes time.

Argument in a [Nut]Shell

So here’s what I think is going on:

Oviraptorids in general are not generalist carnivores — they are specialist carnivores, and this is reflected in their very derived jaws; they are durophages in the broad sense, in that they possess a broadly akinetic skull and crushing platforms in part of the jaw; that they were consumers of eggs, considering both that unlike typical molluscivores or seed-eaters, the floor of the oral cavity does not form a broad, hard palate-like platform, and that rather than a crushing platform of the upper jaw, it possessed what appear to be piercing structures; the jaws are wicked strong, and the jaw adductors are ridiculously huge, far more relative to jaw length than in any other dinosaur, but also that the jaws retained efficiency from the front to the back, rather than developing precision or sectoralized biting regions — implying that biting was strictly orthal (up-and-down) and the object being “bitten” was present along the jaw rather than in a section of it; high degrees of mobility of the jaws suggest that intraoral processing is advanced beyond typical dinosaurian jaws, but was largely propalinal (fore-aft) and orthal, with limited transversal (side-to-side) movement.

Thanks for listening.

Barsbold R. 1977. Кинетизы и особенности строений челюстного аппарата у овирапторов (Theropoda, Saurischia) (Kineticism and peculiarity of the jawl apparatus of oviraptorids (Theropoda, Saurischia)). Трудй – Совместная Совестко-Монгольской Палеотологыческая Зкспедитсия — Joint Soviet-Mongolian Paleontological Expedition, Transactions 4:37-47. (in Russian w/ English summary)
Cracraft, J. 1971. Caenagnathiformes: Cretaceous birds convergent in jaw mechanism to dicynodont reptiles. Journal of Paleontology 45:805-809.
de Queiroz, A. & Rodríguez-Robles, J. A. 2006. Historical contigency and animal diets: The origins of egg eating in snakes. The American Naturalist 167(5):682-692.
Gurney, J. 1992. Dinotopia: A Land Apart from Time. (Harper Collins, New York City.)
Norell, M. A., Clark, J. M., Chiappe, L. M. & D. Dashzeveg 1995. A nesting dinosaur. Nature 378:774–776.
Osborn, H. F. 1924. Three new Theropoda, Protoceratops Zone, central Mongolia. American Museum Novitates 144:1-12.
Schulp, A. s. 2005. Feeding the mechanical mosasaur: What did Carinodens eat? Netherlands Journal of Geosciences – Geologie en Nijnbouw 84(3):345-357.
Zanno, L. E. & Makovicky, P. J. 2010. Herbivorous ecomorphology and specialization patterns in theropod dinosaur evolution. Proceedings of the National Academy of Sciences, Philadelphia 108:232-237. [PDF]

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25 Responses to Osborn Was Right

  1. Alessio says:

    Very, very interesting, i like it when the older theories regain some credibility (assuming you’re right)… But why (it seems) you’re ruling out that they could have also chewed on molluscs or seeds?

    • I am not ruling it out. This post represents an argument for a theory, and so every element in here is something I need to test. This includes the particular foodstuffs a given oviraptorid would eat. I am perfectly capable of accepting differing diets per oviraptorid taxon, generalized omnivory, etc. Practical testing on availability and capability hasn’t been done, and I am trying to see if it can be done for these animals.

  2. jbrougham says:

    Did you consider conifer cones as a food source? Such as large Araucarian cones? Of course there were also bennettite, cycad, pine, cypress, and podocarp cones, ginkgo nuts, palm drupes, and so on. It may be hard to distinguish an anatomy that crushed eggshells from one that worked the scales of cones apart, especially if both are about the same size and shape. Both would involve crunching, but the latter would also involve mandible movements like we see in parrots, crossbills, and the like. In a nutshell, indeed.

    • That is an excellent point, Jason! I had not thought of conifer seeds, and will definitely have to look into it. I will note that part of my argument has been an attempt to integrate the unusual palatal morphology into the dietary system, and in this an object contained within the oral cavity rather than between the jaw tips seems more plausible. However, I will have to integrate that into my testing regimen.

      • jbrougham says:

        Many Cretaceous cones and seeds would be small enough to contact the palate. Moreover, maniraptorans as small as cockatoos destroy cones as large as those of the Bunya Pine (Araucaria bidwillii), which is the size of a bowling ball. They do it just by grabbing scales and ripping them off. Finally, these cone – feeding parrots parrots have a ventrally deep palate, too. It looks superficially very similar to oviraptorids. In parrots the structures are the Angulus caudolateralis palatini, and Pars lateralis palatini, where they surely function in prokinesis, a function which oviraptorids probably did not share.

        • However, these structures in the parrots mentioned are relatively shallow, and rather than having the form as in parrots, in which the pterygoid and the pterygoidal ramus of the palatine provide the major lateral exposure of the palate below the jugal, in oviraptorids the entire apparatus, including the palatine plate of the maxilla and the vomer, are distended. Despite this, though, yes, I see that while parrots can handle large food stuffs, they do so by tearing it to pieces. Parrots, unlike oviraptorids, have a broad expansion of the mandibular symphysis, which forms a deeply triangular “plate” in cross-section, in taxa such as Arini (macaws and the like) where the primary foodstuffs are just as you say, seeds, nuts, and other extremely hard objects. Cracking between two flat and hard surfaces, rather than lightly-built but fixedmandibular halves (ventrally much narrower than dorsally) with a pair of spikes bearing in from the apex. I do not think, but cannot prove without testing, the ability of the lower jaw to substitute as a platform to permit cracking. Even Manabu Sakamoto’s analysis only considered the jaw margins, and I wish to assess the quality of the palatal midline, and pretend that oviraptorids have a function double-set of upper jaw margins, with the inner pair culminating in the ventral spikes. I do not think these features particularly useful for prying seeds out of cones.

          But, like I said, testing! I am adding seed cones to my prospectus.

          • jbrougham says:

            Two last quick points. One, consider the tongue. In parrots it is said to be crucial in prying out seeds, and think of the robust hyoid in Citipati. A strong, rough, trongue could press against those palatal points, either to pinch a cone scale or to crack eggs. Two, try doing a quick thermodynamic calculation to determine how many eggs Gigantoraptor would have to eat to grow and be active. Between 1.4 and 2.2 tonnes of body mass, find the caloric needs for that at homeothermic rates, and how many kCal per liter of egg, and how many eggs of mixed Mongolian ootaxa that would be. If the number is too high then maybe a mixed diet is more likely.

          • I admit that in my interest in this topic I tried to consider Gigantoraptor erlianensis, especially if I were to infer its particular diet from ecology alone, but I do not think data indicates it overwhelmingly as an oviraptorid (a topic supported at least by one recent phylogenetic analysis, Longrich et al., 2010, in their description of Machairasaurus leptonychus). What eggs, indeed? I consider sauropods a good candidate at that size, but also that, unlike oviraptorids, it possessed a much longer mandibular symphysis and if that were to oppose a more conventional flat rather than pointy palate, I would suggest durophagy in the broad sense, but not specifically ovophagy.

            Otherwise, the calculation is definitely an intrinsic part of the projected dietary regime. However, in all honesty, I do not know the equation, so this is a learning experience for me as well — this blog post is designed to help push me into the research.

            Longrich, N. R., Currie, P. J. & Dong Z.-m. 2010. A new oviraptorid (Dinosauria: Theropoda) from the Upper Cretaceous of Bayan Mandahu, Inner Mongolia. Palaeontology 53(5):945–960.

  3. Anonymous says:

    “Moreover, despite several seeming “herbivorous” adaptations, such as lack of teeth, this should not itself result in herbivory: oviraptorosaurs lack the expanded, wide gut of an herbivore, retaining predatory features of the manus and even pes suggesting they engaged in live prey handling. There was, it seems, no direct evidence for herbivory in oviraptorids.”

    Just because oviraptorids lack specialized adaptations for herbivory does not discount an omnivorous way of life. It is entirely plausible that they behaved akin to procyonids and many small, omnivorous mammals today, using their forelimbs to catch small mammals, lizards, and birds and feeding on high-energy, easily digested plant matter like fruits, shoots, and seeds. Additionally, some modern birds, like geese, don’t really have great adaptations for herbivory themselves. They just shove all the plant matter in one hole and hope that the digestive system can work it all out, and whatever doesn’t get digested comes out the other end.

    “This was largely built on the discovery of perinate troodontid skulls in a nest of Citipati osmolskae. Although many possible explanations exist, including random association or predation on the oviraptorid eggs by a troodontid, the first hypothesis might be the most sound: oviraptorid predation on troodontids.”

    It has been suggested that the troodont skulls actually came from a troodontid nest that was uphill (and not contemporaneous) with the Citipati nest. The second nest is really close to the Citipati nest, and the skulls could have eroded from the rock and rolled downhill. At least, this is the suggestion. You are going to need more evidence, though, if you want to use the troodonts as evidence for specialized carnivory in oviraptorosaurs. Many species of living herbivorous lizards, such as iguanas, start out as carnivores or insectivores upon birth and transition to herbivory later in adulthood. If you could find evidence of carnivory in adult oviraptorids, that would probably help a lot in supporting your hypothesis.

    “It is further important to note that I am fairly well-aware of the problem of exclusive egg-consumption related to potential seasonality of egg sources. First, I must be able to determine availability of eggs as a resource relative to time, and then the energetic value of the eggs in question (which would likely use bird eggs such as those of ostrich or other large-egg layers as a model, and go down from there — and try to exclude domestic fowl, for I hope obvious reasons).”

    Most ratites are seasonal egg-layers, though the reproductive habits of ratites are not necessarily indicative of similar habits in dinosaurs.

    The hypothesis seems interesting, but I’m a little skeptical of it. Especially given that herbivorous adaptations have been seen in other oviraptorosaurs (Caudipteryx), suggesting herbivory or omnivory. I could see if oviraptorids were more specialized for a carnivorous diet than other oviraptorosaurs, but the idea that they were nearly exclusive egg-eaters seems implausible, especially given the lack of similar analogues and the implied presence of constraints in what forms are similar (egg-eating snakes and their metabolism). It seems kind of like that whole scavenger-predator thing with T. rex, where it was argued some features indicated scavenging habits despite the only living obligate scavengers having very particular adaptations to that way of life. However, if you can prove this, I say go for it! Good luck!

    • Thank you for the extensive comment!

      As John Hutchinson is fond of saying, I am not here to “prove” a thing, I am here to disprove a bunch of things: I am using the story of egg-eating as a conclusion to what seems most plausible based on trying to discount the alternatives.

      Yes, I am going to have to test the viability of an herbivorous diet, conside the evidence of herbivory in other taxa and see whether that constrains the diet of oviraptorids, and about the association of the troodontid skulls. One problem about that latter is concerns that adjacent nests of very different species would seem implausible, and something I can certainly wait to see the evidence for, as well as test on my own by examining the literature in regards to plausibility. The problem with Caudipteryx, however, is that you describe a post-oral herbivorous processor, and animals like this tend to have large guts for fermenting, otherwise it would be so extraordinarily inefficient (seed goes in, then comes out) as to provide virtually no nutrition. I am skeptical, but must test, the herbivorous question rigorously, by looking at plausible “short-gut” herbivores, or possible pre-gut processing (gizzards and the like). And yes, as for egg seasonality, this is also something I need to test; in many ways, the Ukhaa Tolgod sites are the best, because if I can work to determine seasonal deposition and then associate this with next frequency and density, I might be able to more easily determine if the Ukhaa Tolgod site provides seasonality or was persistent year-round; I can also use the other famous nesting localities, like Egg Mountain and Auca Mahuevo, and see if there is seasonality there. I am not a geologist, so that requires assistance. The greatest part of all of this, I think, is that it will have to be an integrative project: I will need to work with multiple people of differing disciplines to get full comprehensive coverage — I’d rather do it this way than go it alone to make sure what I can say is tempered by experience.

  4. Andrea Cau says:

    The first step in understanding oviraptorid skull morphology would be mapping the sequence of the morhological modifications seen in Oviraptoridae along Oviraptorosauria in order to determine what was oviraptorid adaptation and what was basal oviraptorosaur (non-oviraptorid) exaptation. Did most of the features you mention evolved inside Oviraptoridae or were inherited by a non-oviraptorid oviraptorosaur? Teeth loss was a step-wise sequence: rostralmost dentary teeth first (Incisivosaurus grade) – maxillary and posterior dentary then (Caudipteryx grade) – premaxillary last (Oviraptoridae/Caenagnathidae? grade). The tooth-like palatal processes and mandibular glenoid elongation developed before the skull/mandible had achieved the oviraptorid proportions (at least in the Avimimus grade). Which scenario (if any) these series of modifications support? Additionally, what the differences between “oviraptorine” and “ingeniine” forelimbs and hands tell us on their predatory habits? Which of the two (if any) is the basal oviraptorid condition?

    • I have been somewhat interested in the evolution of the oviraptorid skull, and its dietary implications. I considered these things as I was working on posts like this and this, and other posts in the “diet in oviraptorosaurs” series. While I have also been interested in the evolution of the “ingeniine” manus and its utility, it never bothered me that size of the arm troubles the idea that it could be used in prehension or stabilization: it is something I can test, depending on what plausible feather size I can give it. I also need to test the premise that foot-based prehension is possible, by using Fowler’s data and comparing it among oviraptorosaurs. This part should be pretty easy.

      I am less sure about the ventrolingual projection of the maxilla, a feature that has been said to be present in caenagnathids but based on the published data (Epichirostenotes curriei: ROM 43250) I can derive some doubt, especially as the bone is a bit mashed up. I am unfamiliar with the condition in CM 78000, and so cannot say anything about what it argues. Obviously, the sliding joint at least may precede the ventral processes according to my argument, while they may act as exaptations. I have been involved in another ancillary project of examining extensive avian and testudinine palate and mandibular morpohologies to consider the potential soft-tissue reconstruction, and this has told me largely that in similarly-shaped animals diet between caenagnathid and oviraptorid jaw types must be different, even if the palatal and articular morphologies were present in both. Indeed, even Longrich suggested at one point that Caudipteryx zoui‘s palatal bones were partially distended below the jugal margin, a feature I can’t quite verify — I presume it was rather like that of Incisivosaurus gauthieri, in which the pterygoid/ectopterygoid was exposed ventral to the jugal in lateral view, and leave further distension for testing.

      Remember, all of this stuff I still need to test. It’s one of the reasons I’ve not simply tried to publish this in short forms, by simply saying “it seems so.” It is also why I have been using very couched language on this blog about “what it was I think they ate” — I am trying to make sure that I am not simply making assertions, but making theory and using some facts to form hypotheses.

      • Andrea Cau says:

        According to Senter analyses (2007-2012), some form of hyperextension of pedal digit 2 (at least, at the level of the distal articular surface of the first phalanx of the second pedal digit) is present in Chirostenotes and some (but not all) oviraptorids (e.g., in Citipati but not in “ingeniines”). According to Fowler’s model, we may infer some form of raptor-like behaviour as synapomorphic for the “Chirostenotes-Citipati” node of Senter or, alternatively, as a synapomorphy of the “Oviraptoridae-Caenagnathidae” clade that was lost in the “Ingeniinae” lineage (or a Oviraptorinae-Caenagnathidae convergence): the second scenario may indicate a carnivorous diet for a clade more inclusive than Oviraptoridae and some ecological shift among “ingeniines”.
        More data is needed, for example a comparison between pedal phalanges (and ungual) shapes and proportions among oviraptorosaurs as done in paravians.

        • It is entirely possible that my argument will be contradicted by the intended tests, practical, mathematic and phylogenetic. I at one point felt that Zanno and Makovicky had made a pretty good case for herbivory, but secondary concerns (included those raised by them) forced me to look at the specific data of the taxa, and I became more concerned with testing my original premise, and Osborn’s. Realistically, the title should be “Was Osborn Right?” but I wanted to set off debate with a firestarter, rather than work slowly into the conclusion as I tend to do.

  5. I HATE how people use the fact that O. was found sitting on a nest as proof that O. did not eat eggs. Stupid, fallacious nonsense! Check what theropods with a special liking for eggs today do with their own eggs: golly, they do NOT eat them, but brood them!

    Instead, I do follow your line of reasoning, and find it more convincing than the usual “ohmigodhowcute” reaction :)

  6. Mickey Mortimer says:

    Of course you and I both know what the Oviraptor holotype actually ate- a lizard (Norell et al., 1995). Thus however specialist they were, they were at least generalist enough to eat small vertebrates sometimes.

    I’ll also say Anonymous was right to point out Caudipteryx as an example of a theropod with a narrow body (based on pubes) like oviraptorids, but which has a gastric mill probably not evolved for carnivory. Though as usual for questions involving how Mesozoic dinosaurs lived, I would like data that shows gastric mills aren’t found in avian carnivores, as opposed to just relying on common knowledge.

    • Gastric mill? Not really. I suspect, as do other generalist carnivorous birds, that Caudipteryx would have also swallowed stones for consumption, for whatever cause, but these occur not for developing a post-oral processor without fermentation, useful at least if you are not eating high-fiber, low-nutrition foods (like grasses, etc.); instead, nuts and the like are high-nutrition but require substantive oral processing and a mill (gizzard or gastric). But that’s Caudipteryx. My argument pushes the “faculative herbivore” model away and pushes us back to the idea that not only were they carnivores, but they may have focused on other carnivores, and their eggs. I cannot test the diet of specific eggs, but one of the things I wanted to do was test the efficacy of different size spheroids in the mouth, with different shell thicknesses and correspond those to material testing for eggshell and clamshell, as well as nutshell.

      The thing is, generalist carnivores do not produce specialized oral anatomy; they all look similar, especially with mammals and birds. But introduce a specialist carnivore or herbivore, and you get modifications of the jaw. The oviraptorid jaw (as well as the caenagnathid jaw) is highly divergent from typical edentulous taxa, especially with the development of a palatal complex forming paired median spikes or rounded prominences that projected well ventrally into the oral cavity, and with minimal mandibular contact with the upper jaw (based on the bony surfaces, again, something to look at). This specialized jaw must be developed after a particular feeding regime; it cannot be incidental given how aligned these modifications are for what happens when you push an object contained in the jaw into the palate during orthal and especially protractive adduction. All this to “eat whatever”? is the very premise I am trying to assess. Note I do not claim that Oviraptor (or any other taxon) turned its nose to a handy meal, as even veritable herbivores will take prey when need arises.

      • Anonymous says:

        “The thing is, generalist carnivores do not produce specialized oral anatomy; they all look similar, especially with mammals and birds.”

        Oh, but they do. The plagiaulacoid condition, which is just about the most bizarre dental state in mammals, is probably about as specialized as they get, but morphological analyses have found that the evolution of this feature in numerous unrelated groups (kangaroos, multituberculates, paucituberculatans, plesiadapiformes, etc.) is related to a more generalized diet, not less. See Krause 1982, “Jaw movement, dental function, and diet in the Paleocene multituberculate Ptilodus”; Biknevicius 1986, “Dental function and diet in the Carpolestidae (Primates, Plesiadapiformes); and Dumont et al. 2000, “Abderitid marsupials from the Miocene of Patagonia: an assessment of form, function, and evolution”.

        “The oviraptorid jaw (as well as the caenagnathid jaw) is highly divergent from typical edentulous taxa, especially with the development of a palatal complex forming paired median spikes or rounded prominences that projected well ventrally into the oral cavity, and with minimal mandibular contact with the upper jaw (based on the bony surfaces, again, something to look at).”

        It also needs to be determined that said spikes or prominences weren’t covered by soft tissue like in the palates of mammals. Though such an adaptation could also be interpreted as an adaptation for seed and fruit predation. Moreso, in fact, as seeds normally won’t splatter out like eggs will if you crack them oviraptor-style.

        • I would not say the modification of the plagiaulacoid carnassial-like lower premolar to be severely divergent, as it typically doesn’t correspond to variation in the remainder of the jaw; it is like saying that the occluding tusks of suines makes their whole dentition “divergent” and “specialized,” when the rest remains typically bunodont. One of my much, much longer term projects has been to define sectorialized dentition in reptiles, a topic that is generally relegated to “heterodont” without much to qualify the term. In mammals, I would claim that divergent, specialized dentition should be related to specific processing features, such as the molarless shrew-rat which modified the incisors to act not only in precision grasping but also processing with the development of a lingual, secondary transverse ridge on I1 that forms a trough to “grab” the tips if i1; here, loss of dentition and development of the form of what remains counts as “specialized,” as too the teeth of armadillos (pairs of transversely arrayed cusps), and even sloths (occluding canines, no incisors, and flat, tubular molariforms). Yes, plagiaulacoid “saw teeth” are interesting, and in multituberculates may be very distinct especially when there is corresponding change in the rostral and posterior dentition from typical “basal” mammalian dentition (the “insectivore” condition, such as in zalambdalestids, or zhulestids).

          The nature and function of the spikes is, in fact, of great concern. I’ve spent time considering whether they were covered in either a rhamphotheca, were instead covered by a thickened, cornified pad (as in manatee palates), or instead by epithelium. It should be noted that the cervical and thoracic hypapophyses of Elachistodon and Daspypeltis snakes penetrate the esophageal epithelium, and thus project as bone into the esophagus, exposed and not covered in other tissues. Determine the difference will require direct examination of these various features, something I am already working on.

  7. Duane says:

    Well I’m glad you just came out and stated what you suspect Oviraptors were doing. Now I don’t pretend to know as much about the nuts and bolts of jaw parts/ ortho-lingual mobility etc as some people on here but I do believe it a reasonable premise to suggest that during the Mesozoic there was a lot more eco-space for egg lovers than in the modern Cenozoic. You got any number of dinos pumping out eggs, crocs, sphenodonts, turtles were abundant, ancient birds- hell mammalian monotremes were on the scene as well in greater abundance- egg laying mammals. Now you have basically birds ( K-strategist for most part- few eggs) and reptiles (large ones limited to warm climes for most part). So there is a good possibility for some lines of critters developing an inordinate fondness for eggs in the eMesozoic. Even if largely a seasonal resource fill up when the going is good, put on fat, and make way with small fry until egg season is back. Good luck with future testing. Cheers!

    • I have no doubt about the probability that other animals engaged in egg-eating. This fact was one of the reasons I was beginning to question the hypothesis I was working on years ago. However, as I looked deeper, I realized that egg-eating in typical mammals and birds come from generalist predators; and the same is also true of snakes and lizards. But some animals become very selective about their diet, either constrained by their habitat or they become effective parasites on a species or something, preferring only members of that species for prey. When that selectivity involves unusual foods, I reason, cranial and postcranial anatomy can shift, be selected for by mate preference, and thus become adaptive in the population. I want to see if that’s possible for oviraptorosaurs, oviraptorids in particular, in light of the extremely odd morphology of the jaws. Placing the jaws in a morpho-functional light, it seems they are strange durophages, as assumed by Barsbold, and their jaw mechanics (with both David Smith and Barsbold Rinchen looked at) suggest unusual bite performance. Reconstruction of the jaw muscles based on extrapolating from the EPB and from clear osteological markers on the skull suggest that oviraptorids are doing something that is very, very particular and doesn’t conform easily with other, likely more generalist, theropods. That there are other durophages in the Late Cretaceous sediments that preserve oviraptorids is not a problem, because durophages may easily occupy the same habitat, if their diets were differentiated. Depending on the formation, oviraptorids may easily have been distributed among the brachiopod, gastropod, bivalve, tiny-insectivore, or egg specialist morphologies. The curious question is whether oviraptorids seem adapted to focus on a particular diet, rather than simply leave “can eat eggs” as it is. My argument is that they could, based on their jaw anatomy, and now I must test this.

  8. Alex says:

    Interesting idea but sadly I find it unlikely. I find omnivory/herbivory more likely. Some of the arguments here are rather weak.
    Predatory features in the manus? That does not mean it was used for predation. Therizinosaurus and Deinocheirus were thought to be predators at one point based on their claws.
    Furthermore animals that mainly feed on shelled food have broad, crushing jaws. The beaks of Oviraptorosaurs are rather thin and have more in common with the beaks of herbivorous turtles and Ceratopsians than the jaws of animals that feed on shelled food.
    Also the most primitive Oviraptorosaurs have rather blunt teeth (Incisivosaurus) that don’t seem to indicate obligate carnivory.
    Also the Byronosaurus in the Citipati nest? One interesting suggestion I’ve heard is that Byronosaurus was a nest parasite like Cuckoos.
    There’s also the the Caudipteryx specimen with gastroliths. Not found in obligate carnivores.
    Of course I think omnivory is the most likely diet for Oviraptor. It did have a lizard in it’s stomach and I believe animal bones are more easily fossilized than digested plant matter.

    • I find the counter arguments interesting, but I don’t necessarily agree with them. some of them are suppositions. Turtle beaks between carnivores and herbivores are generally the same. Gopherus and Macroclemys have fairly similar jaw thickness, although the quantification is weak, but the first is an herbivore, the second a carnivore. with respect to birds, the same issue tends to apply: Beak thickness doesn’t vary so much between carnivores, omnivores, or herbivores, especially when dealing with closely related taxa, such as ground finches and Galapagos finches, where relatively minor beak changes signify dietary shifts. Mostly, relative broadness or height of the bill, and its inflection, are better indicators. In this, oviraptorids (and just Oviraptoridae, so far) resemble some herbivorous and durophagous birds (especially finches and parrots). Crushing platforms do not have to be giant plates on both jaws to be relevant: parrots have thin jaws, but robust tongues, which they use to brace against the upper jaw.

      Manus features in some oviraptorids are especially similar to dromaeosaurids. Without implying dromaeosaurids are herbivores, what qualities of the manus would you infer were herbivorous? As for giant theropods like like therizinsoaurids, some have extremely curved claws (Erliansaurus bellemanus) whereas others have extremely straightened claws (Therizinosaurus cheloniformis), but curvature in Deinocheirus mirificus appears reduced in comparison, and resembles caenagnathids (mind you also, that Deino is a omnivore, and likely did practice some grasping with the hands).

      As for teeth in basal oviraptorosaurs, I don’t know how this is relevant, but you’re kinda only half right. First, oviraptorosaurs do NOT equal oviraptorids, and so far I’ve been trying to keep these claims restricted to oviraptorids. This is a special class of toothless taxa with small round heads, not the full range of taxa. Second, Incisivosaurus/Protarchaeopteryx gauthieri is but one basal taxon, and yes is has rounded but scalpel like teeth that resemble some ornithischians in forming a chapping margin and not a sharp edge. But Caudipteryx zoui is a different beast, and has sharp front teeth and have been found with seeds. How do teeth then relate to diet specifically in these cases? Some rodents have no different shaped teeth but are carnivores (kangaroo or tiger mice). The presence of gastroliths in carnivores is known, though: crocodilians consume them for ballast, and they are obligate carnivores.

      No animal has the jaw apparatus as oviraptorids; the few that are similar are almost certainly strange and unusual, so qualifying them based on general, rather than specific, observations becomes a problem. For me as well as you. This is why the project is designed to remove ambiguity.

      As for the association of troodontid skulls with the nest, we have to be careful about such associations. It’s not common, and this would merely be a qualification of my own hypothesis: egg-eaters in snakes and lizards tend to evolve from primary predators of the egg-layers, with primary live prey consisting of nesters then adapting to the eggs of those prey species. We’d expect this behavior, rather than use it as some sort of disproof of egg-adapted feeding mechanisms; eating eggs here is adaptive, not exclusive of other foods.

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