Monday, March 28, 2016

Gigantoraptor: Beast of the Week

This week we will be taking a look at a dinosaur that gave paleontologists valuable information about fossil eggs, and the modern bird connections to prehistoric dinosaurs!  Enter Gigantoraptor erlianensis!

Gigantoraptor with nest life reconstruction by Christopher DiPiazza.

Gigantoraptor was an oviroraptorosaur theropod dinosaur that lived in what is now Mongolia, during the Late Cretaceous, about 70 million years ago.  It's name translates to "Giant Thief/Hunter" in reference to the fact that at a whopping twenty six feet long, it was much larger than other members of it's clade, like Oviraptor, Anzu, and CitipatiGigantoraptor is only known from one partial skeleton which was found to be still growing, so this dinosaur could have have been even larger as an adult.

Gigantoraptor skeletal mount on display in Japan.

Like its relatives, Gigantoraptor had a short, but deep and powerful beak, somewhat similar to a parrot's.  We know this thanks to a well-preserved lower jaw.  Sadly no upper skull has been found from Gigantoraptor yet.  What it used this beak to eat is still a total mystery.  It may have used it to crack open nuts or clip vegetation. Perhaps it was a meat-eater, as well, and used it to break bones?  Gigantoraptor also possessed three hooked claws on each hand and stood on two long, powerful legs.  For an animal its size, it was likely a fast runner.  Although there is no direct fossil evidence of it, Gigantoraptor almost certainly had feathers.

Eggs likely laid by Gigantoraptor with embryo skeleton.

Another really interesting thing about Gigantoraptor is the fact that paleontologists also have discovered its eggs! (and if they arent from Gigantoraptor they are from something EXTREMELY close to it.)  The eggs in question are almost cylindrical in shape, and each measure over twenty inches long!  Some of these eggs were carefully opened to reveal the bones of an oviraptorosaur embryo inside.  The eggs were discovered arranged in a ring formation.  This is typical for what we know about oviraptorosaur nest, thanks to relatives like Citipati, which were found actually brooding over the eggs laid in the exact position.  Gigantoraptor also would most likely have sat in the middle of this ring of eggs with its arms (which had feathers in life) spread over them for protection.  Within the ring of eggs, the eggs seem to have been laid in groups of two.  This is really important to know since it supports the idea that Gigantoraptor, along with many other egg-laying animals, possessed two oviducts in life.  Modern birds, and a few very bird-like nonavian dinosaurs are the only ones that have actually lost one of their oviducts as they evolved. (and do not pair their eggs as they lay them)  We used to think that birds developed this asymmetrical trait to become lighter and fly, but that doesn't explain why flightless dinosaurs like the troodontids evolved the same feature.

That is all for this week!  As always feel free to comment below or on our facebook page!


Wiemann J, Yang T, Sander PNN, Schneider M, Engeser M, Kath-Schorr S, Müller CE, Sander PM. (2015) The blue-green eggs of dinosaurs: How fossil metabolites provide insights into the evolution of bird reproduction. PeerJ PrePrints 3:e1323

Xu, X.; Tan, Q.; Wang, J.; Zhao, X.; Tan, L. (2007). "A gigantic bird-like dinosaur from the Late Cretaceous of China". Nature 447 (7146): 844–847.

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