Baby fossils shed new light on Oviraptorid feeding habits

Oviraptorids are not your usual type of theropod dinosaur. Most people assume that all theropods had jaws bristling with teeth like steak knives ready to eviscerate the next hapless victim they came across, but Oviraptorids actually possessed short deep skulls and toothless jaws. These beaks were initially thought to have been used to crush eggs (the name Oviraptor literally means ‘egg-thief’). When the first Oviraptorid fossil was found in 1924 (Oviraptor philoceratops, Osborn, 1924) it was alongside a nest of what were thought to be Protoceratops eggs, with the Oviraptorid being assumed to be trying to grab a meal. It wasn’t until 1999 (Clarke et al. 1999) and the discovery of a closely related species (Citipati osmolskae) brooding its eggs that it was realised that Oviraptor was more likely caring for its unborn offspring rather than securing its dinner.

This is the manner in which Oviraptorids used to be portayed, as egg thiefs rather than caring parents. Notice the very out of date posture, lack of feathers and horn instead of a crest. Image from midgetonfire.blogspot.com.
This is the manner in which Oviraptorids used to be portayed, i.e. as egg thieves rather than caring parents. Notice the very out of date posture, lack of feathers and horn instead of a crest. Image from midgetonfire.blogspot.com.
The more contemporary view of Oviraptorids. Citipati is shown here brooding on its nest of eggs in a pose that you can still see today in living birds. Image from Clark et al. 1999.
The more contemporary view of Oviraptorids. Citipati is shown here brooding on its nest of eggs, a pose that you can still see today in living birds. Image from Clark et al. 1999.

So what exactly did Oviraptorids eat? Were they herbivores, carnivores or omnivores? These questions are still the subject of some debate by palaeontologists. A new paper, published in the German journal Naturwissenschaften may have discovered new evidence to help sway the argument one way or another.  The paper, by Lu et al., describes a new species of Oviraptorid, Yulong mini and compares it to all known Oviraptorids and other theropods.

Baby dinosaur! This is the juvenile skeleton of Yunlong mini, as well as a line drawing to help you decipher which bones are which. Image from Lu et al., 2013.
Baby dinosaur! This is the juvenile skeleton of Yunlong mini, as well as a line drawing to help you decipher which bones are which. Image from Lu et al., 2013.

When the authors analysed the results of their comparisons, they noticed that the hind limb proportions of Oviraptorids remain constant throughout their whole lives. This is different to most theropods, whose hind limb proportions tend to change as they mature (allometric growth). The interesting thing is that this type of growth (known as isometric) tends to be found in is herbivores. Furthermore, although the individuals found were less than a year old, their limb bones were quite well developed, suggesting they were already able to move around easily. If you couple this with the lack of adult skeletons found at the localites Yulong was discovered, there may be a case for Yunlong possessing precocial development (i.e little/no parental care, effectively born like a mini adult), something again associated with herbivores. Carnivores tend to be altricial, where they are born relatively helpless and require more care take longer to develop.

So was Yunlong and other Oviraptorids herbivorous? We still don’t know for sure. But this new evidence suggests it remains a distinct possibility.

References

Clark, J.M., Norell, M.A., & Chiappe, L.M. (1999). “An oviraptorid skeleton from the Late Cretaceous of Ukhaa Tolgod, Mongolia, preserved in an avianlike brooding position over an oviraptorid nest.” American Museum Novitates, 3265: 36 pp., 15 figs.; (American Museum of Natural History) New York.

Lu, J, Currie, PJ, Xu, L, Zhang, X, Pu, H & Jia, S  (2013) Chicken-sized oviraptorid dinosaurs from central China and their ontogentic implications. Naturwissenschaften 100: 165-175.

Osborn, H.F. (1924). “Three new Theropoda, Protoceratops zone, central Mongolia.” American Museum Novitates, 144: 12 pp., 8 figs.; (American Museum of Natural History) New York.

 

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