Theropod Sterna

["Jaime A. Headden" <qilongia@yahoo.com>]

John Jackson wrote:

<<Apart from the very odd breastplate reversal that would be required
(see above), and the fact that this would make Archae the only flying
bird that had moved its pubis forward, it would require Archae to have
lost a feature (uncinate processes) that have been conserved by 99.95%
of all birds that had them in their ancestry, volant or flightless.
Three "bet-your-
shirt" flight features - probably trap-door developments too.>>

Thomas "Thim" Holtz wrote:

<Except that two of these (sterna and uncinates) are really just
questions of ossification.>

  In other words, the large sternum evolved once in tetanurans, and
developed into various forms (or failed to ossify in adults) in
various theropods? Arcgie would have reduced the bones, as John
Jackson proposed, so how does this affect the origin of flight?

<If we used the breastplate argument, than spinosaurids and
_Sinraptor_ (both of which have fused, keeled sterna) were closer to
modern birds than Archie, dromaeosaurids, oviraptorids, etc.>

  Except that oviraptorids and dromaeosaurids are known to possess
fully ossified sterna with both possessing a crista (or keel), as seen
in specimens GI 100/30 and 100/25 (*Ingenia* and *Velociraptor*,
respectively). (Barsbold, 1983.)

  To quote from that article:

  "[Refering to the Oviraptoridae] A medial projection of the cranial
region of the cleft is sharp and isolated in relief from the adjacant
parts of the sterna." (Barsbold, 1983: 34.)

==
- Often, it is the man who is brought
  down the path to the end who does
  not see his own steps. -

Jaime A. Headden

Qilong, the website, at:
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