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Re: [dinosaur] Oksoko, new oviraptorid from Late Cretaceous Nemegt Formation of Mongolia (free pdf)




There is a time-honored view that the forelimbs of non-avialan theropods were excellent devices for grasping and holding prey. But this doesn't apply to a great many theropods, especially most pennaraptorans. The hands of all pennaraptorans were poorly adapted to grasping small objects with one hand. So they were of no use in climbing trees (this includes microraptorines and basal avialans) or grasping small prey. Large dromaeosaurids likely used their forelimbs to grasp and secure large prey with both hands (such as in the famous _Velociraptor_-_Protoceratops_ tussle), but their hands lacked any real prehension. The same applies to oviraptorosaurs.

I've thought for a while that oviraptorosaur forelimbs were of little (if any) use in foraging, or anything to do with procuring food. The functionally didactyl manus of _Oksoko_ (with a reduced/vestigial third digit) is perhaps not that surprising, given that the forelimb was effectively a wing (or 'pennibrachium' ) with both the second and third digits bound up in skin (as in _Anchiornis_, etc) . So I'm skeptical of Funston &c's hypothesis that forelimb and digit reduction in certain oviraptorids (especially Heyuanninae) is linked to a shift in forelimb function possibly related to diet/foraging. Because two fingers were likely closely appressed and skin-bound, it's doubtful that the relative lengths of the two fingers were tied to any grasping/holding/hooking function.Â

Perhaps the forelimbs of all oviraptorosaurs were exclusively dedicated to non-dietary functions (e.g., nesting, display, grooming, locomotion, defense), and already functionally decoupled from the skull. (I suspect this is the case for the majority of pennaraptorans.) For oviraptorosaurs, I've wondered if the manual claws were retained principally as weapons, especially against members of their own species - as in the wing claws/spurs/clubs used by many extant birds during intraspecific combat. So oviraptorosaurs fought with their wings, with the forelimb and tail plumage used for sexual display - as previously proposed for _Apatoraptor_. However, as noted by Funston &c, these behaviors are extremely difficult to test in fossil species.

Finally, I commend Funston &c for using the correct "caudipterygids" (rather than "caudipterids").ÂÂ Also, the name _Oksoko avarsan_ is a great choice, with a helpful pronunciation for the genus name, and the species name referencing the dark backstory to the specimens.


On Thu, Oct 8, 2020 at 1:50 AM Ben Creisler <bcreisler@gmail.com> wrote:

Ben Creisler
bcreisler@gmail.com

A new paper with free pdf:


Oksoko avarsan gen. et sp. nov.

Gregory F. Funston, Tsogtbaatar Chinzorig, Khishigjav Tsogtbaatar, Yoshitsugu Kobayashi, Corwin Sullivan and Philip J. Currie (2020)
A new two-fingered dinosaur sheds light on the radiation of Oviraptorosauria
Royal Society Open Science 7(10): 201184.
http://dx.doi.org/10.1098/rsos.201184
doi: https://doi.org/10.1098/rsos.201184
https://royalsocietypublishing.org/doi/10.1098/rsos.201184

Free pdf:
https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.201184



Late Cretaceous trends in Asian dinosaur diversity are poorly understood, but recent discoveries have documented a radiation of oviraptorosaur theropods in China and Mongolia. However, little work has addressed the factors that facilitated this diversification. A new oviraptorid from the Late Cretaceous of Mongolia sheds light on the evolution of the forelimb, which appears to have played a role in the radiation of oviraptorosaurs. Surprisingly, the reduced arm has only two functional digits, highlighting a previously unrecognized occurrence of digit loss in theropods. Phylogenetic analysis shows that the onset of this reduction coincides with the radiation of heyuannine oviraptorids, following dispersal from southern China into the Gobi region. This suggests expansion into a new niche in the Gobi region, which relied less on the elongate, grasping forelimbs inherited by oviraptorosaurs. Variation in forelimb length and manus morphology provides another example of niche partitioning in oviraptorosaurs, which may have made possible their incredible diversity in the latest Cretaceous of Asia.

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News and blogs:

Say hello to Oksoko!

https://gregfunston.com/2020/10/07/oksoko/

https://www.ed.ac.uk/news/2020/lost-digits-point-to-spread-of-parrot-like-dino

https://www.bbc.com/news/uk-scotland-edinburgh-east-fife-54448253

http://novataxa.blogspot.com/2020/10/oksoko.html

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