OVIRAPTOROSAURIA! Part Two [Taxa and Phyllogenetics---Primitive forms and Caenagnathids]

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

WE INTERRUPT THIS REGULARLY-SCHEDULED DINOSAUR LIST DISCUSSION TO
BRING YOU THE FOLLOWING:

  Much of Jaime A. Headden's study has come in the form of researching
the actual oviraptors themselves, and has resulted in a few heresies.

  The clan of the oviraptors is varied in geography, and seems to
split into two lineages, the Caenagnathidae and the Oviraptoridae,
united as the Oviraptoroidea, and is contained within the higher taxon
Oviraptorosauria by inclusion of an outgroup, the single taxon
*Microvenator*, and possibly the taxon *Avimimus* (which will not be
discussed further).

  Jaime A. Headden goes on to describe the individual taxa:

  "The oldest of these animals was *Microvenator celer*, whose name
means the 'fast little hunter', and was found in the Cloverly
Formation of Utah in the USA, at the end of the Early Creataceous in
the Albian through Aptian transition. Based on a juvenile skeleton
that may only be half-adult size, *Microvenator* was 2 feet long, or
.6 meters, and weighed 7 or so pounds or close to 4 kilograms (adult
length was about 4 feet or 1.2 meters, and weight was about 15 pounds
or 7 kilograms). The very long legs of this animal would conceivably
not shorten much to adulthood, so this creature may very well have
been a fleet-footed and short-armed oviraptorosaur, and its position
as the most primitive is shown in the the structure of its
ornithomimid and ornitholestid-like ilium and pectoral girdle, but
advanced in the form of its femur with the anterior position of the
lesser trochanter at the head. Microvenator's phyllogenetic position
is somewhat doubtful, but because of its suite of characters of both
ornithomimids and oviraptorosaurs, it can be assumed as a transistory
form between one group and the other, and may also be a taxon derived
from the most recent common ansector of the that said taxon. This
would place oviraptors as the sister group to ornithomimids, but
closer to dromaeosaurs than to the ostrich-dinos.

?--+--+--Arctometarsalia
   |  +--+--Ornithmimosauria
   +--+--+--Ornitholestidae
      |  +--+--Oviraptorosauria
      |     +--+--Microvenator
      |        +--+--Oviraptoroidea
      |           +--all other oviraptorosaurs
      +--Dromaeosauridae

   <<Clade describing position of *Microvenator*>>"

  The lineages seem to split here, for the earliest of each group
after *Microvenator* are derived enough from each other to described a
ghost taxon between *Microvenator* and all other taxa.

  "Living much later was *Caenagnathasia martinsoni*, whose name means
'Martinson's recent jaw from Asia' and was found in the Bissekty
Formation of Uzbekistan, in the late Turonian. Based on two partial
mandibles, one the pair of fused dentaries, and the other a nearly
complete dentary with partial fusion to a broken opposite dentary.
*Caenagnathasia* was adult and would have measured about 4-5 feet or
1.2-1.5 meters long and weighed 15-20 pounds or 7-9 kilograms. The
primitive state of the jaws shows remnants of the dental alveoli, now
degenerated into pits along the dentary's lingual edge forming troughs
and two lingual ridges (on on each side of the jaw) that show an
eveolutionary trend towards true toothlessness. It was possible
*Caenagnathasia*, whom I call 'Freckles' for both the very foraminated
nature of the dentaries and a restoration I've done of him, was the
ultimate oviraptoroid, basal to both oviraptorid and caenagnathid
lineages, but the structure of another caenagnathid's mandible would
refute this [see later]."

  At this point, Jaime pauses to catch his breath. This enterprising
amateur seems very excited, and it would appear that *Caenagnathasia*
is the favorite oviraptor in this case. A demonstration shows that
*Caenagnathasia* would have fit in the cradle on one's arms very well,
with room to spare, the size of a very large domestic feline. It seems
unusual that such a group of animals like dinosaurs would produce such
giant predators like *Tyrannosaurus* (the most massive, and still
biggest) and *Giganotosaurus* (the longest with the biggest skull) and
yet produce small frail animals like *Caenagnathasia*. Jaime continues
on to the next taxa:

  "For breath's sake, I'll cut this one short, 'cause there's not much
to say on him. *Elmisaurus rarus*, which means 'rare foot lizard
[sic]', was a massive oviraptor, but small, very small, the size of a
large dog, has very developed ankles and metapodials unlike any other
caenagnathid. It was the last caenagnathid, too, up in the Nemegt,
which was a Mongolian formation that occured at the same geological
time as the Hell Creek and Lance Formations of North America. Based on
manus bones and feet, he was stocky, short-handed (like all
caenagnathids compared to oviraptorids) and short-footed, though would
have been one tough cookie. About as massive as a *Deinonychus*, but
smaller. 100 pounds or 45 kilograms max., a mere 6 feet or 1.8 meters
long.

  "I've got to say, this one's a strange taxon to sort out, and I
won't presume to say 'This is the answer to the whole puzzle'. This is
my findings. *Chirostenotes pergracilis* and *Caenagnathus collinsi*
are synonymized, based on parsimony and a jaw fragment described in
Sues, 1998. This has actually been suspected since the 40's, but not
proof was made back then. *Chirostenotes pergracilis'* name means
'very slender narrow hands', and they are, too. The feet on this
animal are similar to *Elmisaurus*, but less robust and fused, even in
the larger forms. He comes from the Judith River Formation of Dinosaur
Park, Alberta, in Canada. 6 or so feet and 1.8 to about 2 meters,
weighing about 80-90 pounds or 35-40 kilograms. Not as big as some,
but big. Jaw structure of the type species show advanced,
oviraptorid-like development, but lacking the mandibular prong that
makes oviraptorid jaws stick out, and it [the jaw] is elongate and
narrow, not as bowed as in *Caenagnathus* or oviraptorids. What seems
odd is that there could be up to three species or three genera in this
taxon. *Chirostenotes sternbergi* (which Sues synonymizes with *'O.'
elegans* [later] as *C. elegans*) is short jawed, and possesses more
defined lingual ridged like *Caenagnathasia* than the type species,
but is elongate and point-tipped, unlike 'Freckle's' chinned jaw
[without allusions to Godzilla] and denticulated beak. It would seem
that *C. sternbergi*, con-geographic with *C. pergracilis*, could be a
sister taxon to both genera, and as such may also represent an
intermediate form between the two, possibly derving of its own generic
identity; the animal was smaller but probably as massive, so length is
about 5.5 feet or 1.7 meters. The situation with *'O.' elegans* as
synonymous with C. sternbergi is shallow, for the former is
representative only of metatarsi that, while possibly belonging to C.
sternbergi, show a morphology differing from the jaw, which is more
robust than *C. pergracilis*, yet the metatarsals are more gracile
than *C. pergracilis'*. This 'species' is difficult to define on only
metapodials. Last comes *C.* sp. a jaw refered to this genus by
Currie, Godfrey, and Nessov 1995, and represents a jaw about as long
as the type's, but much more robust, similar superficially to
oviraptorids. This specimen was found in the Hell Creek Formation of
Montana, USA, and shows an animal _much_ more robust than either
*Elmisaurus* or *Chirostenotes pergracilis*, and could very well
represent a taxon of generic identity separate from either former
taxa. The nomen *Chirostentotes 'robustus'* is hereby suggested.
Length was about 6.5 feet or 2 meters, and weight was probably close
to 120 pounds or 55 kilograms.

?--+--+--Arctometarsalia
   |  +--+--Ornithmimosauria
   +--+--Ornitholestidae
      +--+--Oviraptorosauria
         +--+--Microvenator
            +--+--Oviraptoroidea
               +--+--Caenagnathidae
                  |?-Caenagnathasia
                  |--+--Chirostenotes sternbergi
                  |  +--+--Chirostenotes pergracilis
                  |     |--Chirostenotes sp.
                  |     +--Elmisaurus rarus
                  +--Oviraptoridae
"

  Having said all this, Jaime needs a break, and will get back to the
Oviraptoridae when a headache has finish ravaging the poor amateur.

  To be continued ... again....

  Jaime A. Headden
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