Evolution of Reproductive Traits in Theropods

In an ongoing study published as a series of papers to date, we investigate the eggs, nests, eggshells, and associated skeletons of maniraptoran theropods in order to provide insight into their paleobiology and to shed light on the evolution of traits related to reproduction among theropods. Our results show that several avian characteristics evolved first among theropod dinosaurs, whereas other traits are either primitive for archosaurs or unique among dinosaurs.

fossilized maniraptoran nest

Top view of fossilized maniraptoran nest (TMP 2007.4.1) from the Two Medicine Formation, MT.

 fossilized maniraptoran nest

Technical illustration of nest. Scalebar is 10 cm. Illustration © Donna Sloan.

 fossilized pelvis and hind limb of a gravid oviraptorisaur

Left side view of the fossilized pelvis and hind limb of a gravid oviraptorisaur (NMNS-VPDINO-2002-0901).

fossilized pelvis and hind limb of a gravid oviraptorisaur

Right side view of same specimen. Scalebar is 10 cm. Images © American Association for the Advancement of Science.


Zelenitsky, D.K., and Therrien, F. 2008. Unique maniraptoran egg clutch from the Upper Cretaceous Two Medicine Formation of Montana reveals theropod nesting behaviour. Palaeontology. 51: 1253-1259.

Zelenitsky, D.K., and Therrien, F. 2008. Phylogenetic analysis of reproductive traits of maniraptoran theropods and its implications for egg parataxonomy. Palaeontology. 51, 807-816.

Zelenitsky, D.K. 2006. Reproductive traits of non-avian theropods. Journal of the Paleontological Society of Korea. 22, 209-216.

Sato, T., Cheng Y., Wu, X., Zelenitsky, D.K., and Hsiao, Y. 2005. A pair of shelled eggs inside mother dinosaur. Science. 308, 375.

Zelenitsky, D.K., Modesto, S.P., & Currie, P.J. 2002. Bird-like characteristics of troodontid theropod eggshell. Cretaceous Research. 23, 297-305.