Mamas little theropod

Regardless of sexual dimorphism in non-avian theropods, what we know about their reproductive biology has been greatly enhanced by the discovery of brooding oviraptorosaurs. Several recently discovered articulated oviraptorosaur skeletons are preserved overlying nests of eggs, laid in a circular pattern of as many as 22 eggs. The embryos are the same species as the adult skeleton overlying them.4 The oviraptorosaur skeleton (Mom? Dad?) is positioned directly above the center of the nest, with its limbs arranged symmetrically on either side and its arms spread out around the perimeter as if protecting the nest (Figure 9.25). These specimens indicate that incubating eggs on open nests evolved well before the origin of modern birds.

What we know of the post-hatching growth of non-avian theropods mostly comes from bonebeds (for example, Ghost Ranch (New Mexico) and Cleveland-Lloyd (Utah)), as well as from some of the Upper Cretaceous localities of the Gobi Desert in Mongolia. For Coelophysis and Syntarsus, apparently there was a 10- to 15-fold increase in body size from hatchling to adulthood, and this growth is thought to have been quite rapid. Accompanying

Figure 9.25. Specimen of an oviraptorosaur adult nesting on its eggs.

4. The eggs were first attributed to the ceratopsian Protoceratops. Because they were found with theropod skeletons, it was assumed that the theropods were stealing the "Protoceratops eggs" and were given the name Oviraptor (= egg stealer). Oviraptor languished, falsely accused, for 70 years, until the mid-1990s discovery of the unquestionably nesting specimens.

Figure 9.25. Specimen of an oviraptorosaur adult nesting on its eggs.

4. The eggs were first attributed to the ceratopsian Protoceratops. Because they were found with theropod skeletons, it was assumed that the theropods were stealing the "Protoceratops eggs" and were given the name Oviraptor (= egg stealer). Oviraptor languished, falsely accused, for 70 years, until the mid-1990s discovery of the unquestionably nesting specimens.

this rapid growth were proportional changes in the skull (relatively smaller eye socket, enlargement of the jaws and areas for muscles), relative lengthening of the neck, and relative shortening of the hindlimb. Similar changes - when they can be identified - are thought to occur in Tarbosaurus and Albertosaurus as well.

Was this article helpful?

0 0

Post a comment