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Whats in a Name? (Part 2)July 23, 2014

What’s In A Name? (part 2)

Oviraptor TDPlogo

 

Let the paleontology adventure continue!  As promised, I am back with more on the oviraptorid story.  Last time on our Nature’s Art Village blog, I shared with you the righting of the great wrong that was perpetrated against the name and character of Oviraptor philoceratops and related dinosaurs in the oviraptorid clade (Family: Oviraptoridae).  With the first installment of this riveting scientific exploration, I posted this picture of the famous oviraptorid clutch with a fossilized Citipati osmolskae having clearly died while brooding these eggs.  This beautiful specimen has been nicknamed “Big Mamma”!  Big Mamma was of great importance to discerning the true intentions of the first Oviraptor discovered.  It is also of great value to continuing to learn more about their lives and behaviors.  In this post, we will look closer at the eggs and the bone histology of the broody, the one who incubates and protects the eggs.  With these foci, we can learn a great deal about the overall reproductive behaviors of these magnificent dinosaurs and their extant descendants: birds.

Let’s first take a look at the eggs.  They are tightly paired and have been found this way in multiple oviraptorid clutches.  The pairedness of eggs in oviraptorid nests suggests two possible scenarios: (i) the eggs were laid and then arranged in pairs, or (ii) the eggs were laid simultaneously.   A recent study of an oviraptorid pelvic specimen has revealed eggs that developed at the same time in two fully-functioning oviducts.  Furthermore, in the pelvis the more pointed end of the eggs was facing the tail and in the ring-shaped clutches the more pointed end of the eggs was oriented towards the nest perimeter.  This fits with the model of oviposition (the process of laying eggs) wherein the female moves to the center of the nest to lay her eggs.  Modern birds are born with two functional oviducts, an evolutionary trait evident from their ancestral dinosaurian origins.  Over time, however, the right oviducts in modern birds regress to a weak, unusable state.  This is hypothesized to be a weight-reduction adaptation necessary for flight.

Jurong_Southern_Cassowary

 

The number of eggs in these famous oviraptorid clutches also indicates that more than one female laid eggs in a single nest.  The group of modern birds known as Paleognathes (the basal* lineage of living birds), including emus, ostriches, and cassowaries (pictured above), share this habit.  Another reproductive trait shared by basal extant birds with their ancestors may be the parent that actually sits on the nests.  One image we have of birds in their nests is the hen incubating her eggs.  It can seem obvious to us that the female bird would take on this role.  But if we go to our paleognathes, we see just the opposite.  With almost all paleognathes, the males build the nests, brood the eggs, and raise the young.  This may also be the case with oviraptorids!  A recent study found that the large number of eggs in oviraptorid clutches is representative of the large number of eggs also found in paleognathes clutches – evidence for paternal care only.  It also found that a special kind of bone called medullary bone, deposited in the long bones by female birds during reproduction, was lacking in all limb bone samples from the Citipati nest specimens.  This indicates that the oviraptorids incubating the eggs were actually male!

So what’s in a name?  The name Oviraptor used to be synonymous with a thieving, conniving criminal – not the kind of animal you’d want to be friends with!  But that perception has changed thanks to paleontological studies.  And now Big Mamma here might actually be Big Papa!  Certain regions of Mongolia appear to be a treasure trove for oviraptorid fossils so I am sure that new discoveries will soon offer us even more clarification.  Why not stop by The Dinosaur Place at Nature’s Art Village and take a peek at our Oviraptor replicas with their nest and babies?  And make sure you check out the real dinosaur eggs for sale in our Gallery while you’re here!

 

Dinosaur Eggs (2)

 

*basal – this term refers to the early members of a new group which gave rise to later members with their own unique specializations.   It is a neutral way to say “primitive” since that has negative connotations and is not preferred language within the scientific community.

 

 

Clark, James M., Norell, Mark A., and Rowe, Timothy. 2002. Cranial Anatomy of Citipati osmolskae (Theropoda, Oviraptorosauria), and a Reinterpretation of the Holotype Oviraptor philoceratops. American Museum Novitates, 3364.

 

Norell, Mark A., Clark, James M., Chiappe, Luis M., and Dashzeveg, Demberelyin. 1995. A nesting dinosaur. Nature, 378;28.

 

Plum, Richard O. 2008. Who’s Your Daddy? Science, 322.

 

Sati, Tamaki, Cheng, Yen-nien, Wu, Xiao-chun, Zelenitsky, Darla K., and Hsiao, Yu-fu. 2005. A Pair of Shelled Eggs Inside A Female Dinosaur. Science, 308.

 

Varricchio, David J., Moore, Jason R., Erickson, Gregory M., Norell, Mark A., Jackson, Frankie D., Barkowski, John J. 2008. Avian Paternal Care Had Dinosaur Origin. Science, 322.