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Jeholornis; the flying basal Ovi was (Re: Incisivosaurus gauthieri images)



Hi all,

I have been discussing this with HP Aspidel for a while, but now that this
animal has popped up, I want to share something with you: an interesting
hypothesis. <Yes, yes, sounds good!> Remember HP Greg Paul <Huh? Who? :))and
his fantastic book about the Dinosaurs of the Air in which he further
elaborates his hypothesis that at least most of the advanced Maniraptora,
are neoflightless? You have been living living underneath a rock if this has
all gone by you, but that is not the point, the point is, that within a
group of animals, there has been an animal discovered which shows
neoflightlessness is a good possibility of explaining the numerous advanced
flightrelated features seen in e.g. Dromies and Ovies. In this case, the
latter is the most important of the two.

The first link of the two provided by HP Aspidel is the most important one
in this hypothesis, because of, as said above, contains the detailed skull
drawing we all have come to love for this new genus and for the first time,
non-Nature subscribers (like me) were able to see the shape of the lower
jaw. This element of the entire skull is in my eyes the most important,
since it already shows the basis design seen in the advanced Oviraptorosaurs
and Avimimus in general structure, but if you look at it, you have the
distinct feeling that you have recently saw a near similair structure in
another new genus from Liaoning which was recently published. I am talking
about Jeholornis prima (tada!), a supposed arboreal proto-bird. Here I will
advocate that this other recently described is a arboreal basal Ovi of some
sort.

The lower jaw was the first thing that made me think of this, this was so
similair to the condition found in Caudipteryx, Incisivosaurus,
Caenagnathids and Oviraptorids to a smaller degree, also to some degree in
the Segnosaurids, but they still have all of their teeth preserved, so they
may have came from an earlier radiation of Jeholornis like birds. The second
character observed in the skull is the reduced maxilla and this is observed
in Incisivosaurus, Caudipteryx, Citipati osmolskae, Khaan mckennai and
"Oviraptor" mongoliensis (the only genera in my files with decent skull
material preserved; Ingenia is left out due to the questionability of the
validity of the referred specimens to this genus). Another feature in the
skull, and this time the mandible, is a feature we already saw in
Epidendrosaurus, which will lessen the importance of the characteristic
within Jeholornis unfortunately, is the well ossified symphysis. Again this
is seen in all of the above mentioned Ovi's, although the condition in
Caudipteryx and Incisivosaurus is uncertain due to the fact that the former
does not have a complete mandible known with a left and right side (at
least, not drawn) and that of the latter genus no dorsal view of the
mandible is available to me. The jugal shows a distinct curvature upwards,
which approaches the condition seen in the Ovi's, but not totally, this is
to be expected within a basal genus of a clade.
Fifth, the near-mesopubic condition, which is a clear reversal from the
condition seen in Archaeopteryx, which has a strong opisthopubic condition.
A mesopubic is also a condition seen in Ovi's, though the distal curvature
seen in at least Ingenia makes it appear to look like a propubic-conditon.
Last, but not least, the similarities in the the caudal count. The reduced
caudal count is something that appears to be almost diagnostic for the
Enigmosaurs and this is best seen in genera like Caudipteryx and Nomingia
were complete caudal counts can be observed.
A pylogostyl is not evident in the preserved material known for Jeholornis,
but it is also not found in Caudipteryx and therefore might be a secondary
adaptation for Nomingia.

This has been my two cents... and my longest post to the DML yet! :)

Cheers,

Rutger Jansma