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Henri Rönkkö wrote-
All right. So what is the earliest known bird
having a kinetic skull called?
Well, Protopteryx probably had a kinetic skull, as
it lost the postorbital-orbital contact and probably the quadratojugal-squamosal
contact. However, the presence of a craniofacial hinge cannot be
ascertained from the literature and an ectopterygoid was probably still present,
limiting movement compared to modern birds. Enantiornithines certainly
lost postorbital-orbital and quadratojugal-squamosal contact and I think had
craniofacial hinges, although they still had ectopterygoids, so their kinesis
was probably not as well developed as neornithines either. Hesperornithids
are the most basal birds to be described with a prokinetic skull. Perhaps
earlier euornithines like Patagopteryx or Chaoyangia had prokinesis too, but
this is undescribed at present.
Further discoveries may complicate the picture
however. The alvarezsaurid Shuvuuia has a prokinetic skull and
Archaeopteryx was recently reported (Elzanowski, 2001) to have a form of cranial
kinesis different from any living bird. I'm unsure of the condition in
more basal theropods, although I'm fairly certain no other non-avian theropods
have been found with prokinetic skulls.
Mickey Mortimer
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