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Matt Troutman wrote..
> The uncinate processes in dromaeosaurs are
> secondary ossifications (not extentions of the thoracic ribs in
> ornithurine birds).
Sometimes it's tricky to tell whether or not uncinate processes on
maniraptoran ribs had their own, separate centres of ossification. If
you look closely at the uncinate processes in some ratites -
particularly moa, and I have seen it in cassowaries and I think
ostriches too (emus, like GSP says, do not have uncinates on their
ribs... I checked lots of specimens hoping to disprove this:)) - the
uncinate is not fused to the rib. This is a problem in curation and
exhibition, because of course the uncinates then drop off and can get
lost, so lots of curated ratite specimens have the uncinates stapled
or wired onto the rib. This problem is superbly illustrated by
the _Dinornis_ on display in the main hall of the NHM (London) (where
one of the fibulae, incidentally, has already fallen off its natural
If palaeognaths do have a basal position in Neornithes (i.e. are the
sister-group to Neognathae), then might 'uncinates fully fused to
ribs' be a neognathan character? Or have ratites reversed a primitive
ornithurine condition? Diagrams of hesperornithiformes,
ichthyornithiformes and of course _Chaoyangia_ seem to show the
uncinates as unfused, so maybe the former idea is the best
one. I'm really despairing at how little I know.
"Slimy? Mudhole? My _home_ this is"