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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
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
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?).