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RE: Ah ha! That's where therizinosaurs came from
Ron Orenstein wrote:
<That's the biggest problem with concluding that oviraptorids etc are
secondarily flightless - where is the unquestionably volant clade into
which they fit? Of course it could turn up any day (and I assume Greg
Paul will argue that it already has, but not everyone has tumbled to it
This kind of actually starts with the recovery of *Protarchaeopteryx robusta*
as an oviraptorosaur, which has arms close to the length of its legs -- which
are themselves not terribly short. A short tail (<30), although no evidence of
a pygostyle, adds to the argument that whatever ancestor it had, if we take
*Caudipteryx zoui* as a descendant, would have had a short tail, long legs, and
potentially longer arms. Here, we place our taxa on a cline with an even
longer-armed, short-tailed oviraptorosaur wouldhave existed. Despite that
separate sternal plates are preserved in both taxa, with short scapulae and
large, rounded and short coracoids, we might assume that the arm length alone
with the short tail would be enough to infer "flightness" in the ancestor.
As Tim Williams continually points out in this debate, and in connection with
the Dececchia & Larsson paper just recently published by _PLoS ONE_, there must
be a way to distinguish an actual FLIGHT-character from a character in which
the function may be related, but not essentially for flight. This is something
Paul has not done, and which is I think generally futile as there are few taxa
we can actually assess the mechanical properties of which exhibit these
features, are not themselves related to actual fliers, and thus can be used to
discriminate "true" and "apparent" flight characters.
That said, it has been bandied about that *Omnivoropteryx sinousaorum*
(Czerkas & Ji, 2002) and taxa like it (*Sapeornthidae*) represent
oviraptorosaur-like taxa. Wroteth the Mickey
"Phylogenetic Relationships- The only oviraptorosaur-like characters are the
short snout, ventrally displaced premaxilla and anterior maxilla, decurved
dentary and elongate external mandibular fenestra. The first is common in
basal birds, especially Jeholornis. The third is also found in Jaholornis,
while the third is seen in confuciusornithids. The second character is not
known in eumaniraptorans."
Like sapeornithids, and avialaeans, and unlike oviraptorosaurs, we get things
"more than ten
dorsal vertebrae, scapula decreases in wifth distally, acromion does not
project dorsally(?), distal scapular shaft curved to be concave dorsally,
distal humerus strongly curved anteriorly/laterally, radius about 1/2 of
ulnar width, distal radius abruptly expanded, metacarpal I ~1/7 of
metacarpal II length, phalanx I-1 ~1/2 of metacarpal II length, phalanx I-1
slender, phalanx II-2 distally expanded(?), phalanx II-2 shorter than
phalanx II-1, pubic symphysis ~1/3 pubic length, pubic shafts bent
posteriorly around midlength, pubic boot projects mostly posteriorly,
metatarsal V absent(?), elongate metatarsal I, phalanx II-2 subequal in
length to II-1, distal phalanges of pedal digits III and IV elongate
compared to penultimate phalanges. While a few of these might be expected
in a convergently volant oviraptorosaur, many have no particular relation to
So concludeth the Mickey: "So Omnivoropteryx is not a volant oviraptorosaur,
but is a
I have a hard time seeing sapeornithids (any of them) as oviraptorsaurs. The
skulls (e.g., Zhou & Zhang, 2003) are superifically similar (and by
superficially, I mean cherry-picking specific oviraptorosaurs and ignoring
others, like for example *Incisivosaurus gauthieri*) but seem to differ in the
details, or are represented broadly among maniraptorans, like *Scansoriopteryx
heilmanni* (Czerkas & Yuan, 2002) and *Epidexipteryx hui* (Zhang et al. 2008).
Needless to say, though, this will not be the last we will hear on this
subject, as I am sure new future basal oviraptorosaurs will come out, and the
skull of *Similicaudipteryx yixianensis* (He et al., 2008) has yet to be
described from recently published new specimens (Xu et al., 2010).
I have an image in mind which depicts my predicted basal oviraptorosaur, but
will get into that in some future time.
Czerkas, S. A. & Ji Q. 2002. A preliminary report on an omnivorous volant bird
from northeast China. in Czerkas (ed.) Feathered Dinosaurs and the Origin of
Flight. The Dinosaur Museum Journal 1:127-135.
Czerkas, S. A. & Yuan C. 2002. An arboreal maniraptoran from northeast China.
in Czerkas (ed.) Feathered Dinosaurs and the Origin of Flight. The Dinosaur
Museum Journal 1:63-95.
He T., Wang X.-l. & Zhou Z.-h. 2008. A new genus and species of caudipterid
dinosaur from the Lower Cretaceous Jiufotang Formation of western Liaoning,
China. Vertebrata PalAsiatica 46(3):178-189.
Xu X., Zheng X. & You H.-l. 2010. Exceptional dinosaur fossils show ontogenetic
development of early feathers. Nature 464:1338-1341.
Zhang, F.-ch., Zhou Z.-h., Xu X., Wang X.-l. & Sullivan, C. 2008. A bizarre
Jurassic maniraptoran from China with elongate ribbon-like feathers. Nature
Zhou Z.-h. & Zhang F.-c. 2003. Anatomy of the primitive bird Sapeornis
chaoyangensis from the Early Cretaceous of Liaoning, China. Canadian Journal of
Earth Sciences -- Revue canadienne de sciences de la Terre 40:731-747.
Jaime A. Headden
The Bite Stuff (site v2)
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion