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RE: First dinosaur eggs found ready to lay in mothher



Jeff Hecht wrote:

The pelvis of an oviraptor includes two eggs with shells in place, almost ready to lay, showing that theropods had two working oviducts, in contrast to the one of birds. It also shows that dinosaurs laid pairs of eggs in a series of sittings to make a whole clutch, not a whole batch at once. The paper is in the just-out Science; the story with photos is at
http://www.newscientist.com/article.ns?id=dn7267

From the article:

The fossil "is absolutely stunning", says Ken Carpenter of the Denver Museum of Nature and Science in the US. Capturing a moment so close to when a female dinosaur was to lay her eggs makes it "one of the most remarkable discoveries yet".


I couldn't agree more.

AFAIK, the condition in the vast majority of Mesozoic birds is unknown. Thus, one or more of the avialan clades (_Archaeopteryx_, enantiornithines, hesperornithiforms, etc) may have retained the twin-oviduct condition seen in oviraptorosaurs. When did the single-oviduct condition first arose in Avialae? Phylogenetic bracketing tells us the first neornithines had it - but we can't push the bracket down the tree any further (or can we?).

Cheers

Tim