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Re: Support for Enigmosauria



Ken Kinman wrote-

>      Anyway, he seems to be doing a great job of separating the "wheat
from
> the shaff".  Many proposed synapomorphies on that long "laundry list" are
> clearly found in other groups besides "enigmosaurs", and of those examined
> so far, two possibilities seemed to have survived: (1) ectopterygoid
lateral
> to palatine and (2) reduced basipterygoid processes.  Whether either of
> these will survive further scrutiny remains to be seen (and it seems
likely
> they could very easily be parallelisms that did not occur in more
primitive
> forms of a paraphyletic "enigmosauria".
>      Of the characters that have not been scrutinized, there are seven
that
> may still pass muster, but I am not particularly optimistic since these
> lists seem to have far more "shaff than wheat".

Two characters!?  You think only two characters in that entire list are
probably valid?  (plus the seven possible ones)  Character distribution in
the real world is not a Sereno-esque eden of perfectly congruent layers of
0's and 1's corresponding exactly to clades.  If it were, our trees would
have consistancy indices of 1.00.  In actual analyses, the values are far
lower (Holtz 2000- .442; Norell et al. 2001- .44; Rauhut 2000- .42).  If
they were close to 1.00, theropod phylogeny would be so obvious we wouldn't
need these huge analyses.  You have to expect that other clades will develop
enigmosaur-like characters in parallel, and that some enigmosaurs will lose
characters originally diagnostic of the clade.  The following seem to be
good enigmosaur characters-

- external naris longer than antorbital fenestra
Found in Erlikosaurus, Caudipteryx sp. nov. and oviraptorids.  Also in
avians, not in Caudipteryx zoui.
- caudal margin of naris passing rostral border of antorbital fossa
Found in Erlikosaurus, Caudipteryx and oviraptorids.  Also in Scipionyx
(ontogenetic?), Ornitholestes, Shuvuuia, Byronosaurus, Bambiraptor
(ontogenetic?) and avians.
- posterior section of premaxilla toothless (modified from Sues, 1997)
Present in Erlikosaurus, Caudipteryx and oviraptorids, also in derived
ornithomimosaurs and some pygostylians.
- promaxillary fenestra absent
Erlikosaurus and Chirostenotes lack one, Caudipteryx has a promaxillary
fossa and oviraptorids might be variable.  Khaan has one, but Citipati and
Conchoraptor may not.  Most pygostylians don't either (Sinornis being the
exception).
- ectopterygoid lateral to palatine (no ectopterygoid-palatine fenestra)
(Sues, 1997)
Seen in Erlikosaurus and oviraptorids.
- reduced basipterygoid processes (Russell and Dong, 1994)
True in Erlikosaurus, Nothronychus, Chirostenotes and oviraptorids.
- dentary symphysis decurved (Norell et al., 2001)
An often abused character, certainly seen in several segnosaurs,
Caudipteryx, Microvenator and Conchoraptor.  Chirostenotes and most
oviraptorids don't seem to actually have this condition though.  Also
developed in some ornithomimosaurs and specimens of Shuvuuia.
- dentary symphysis deflected medially (Makovicky and Sues, 1998)
Present in Alxasaurus, Nothronychus, Erlikosaurus, Chirostenotes, possible
Caudipteryx, Microvenator and oviraptorids.  Also seen in derived
troodontids.
- coronoid absent (Russell and Dong, 1994)
Most oviraptorids don't preserve coronoids, so they were thought to be
lacking in the group until Citipati was found with a tiny one.  At least
Erlikosaurus and Chirostenotes lack any articular surface for coronoids, so
are presumed absent.  Ornithomimids, Shuvuuia and avians also lack
coronoids.  A tiny bone in the naris of a Caudipteryx specimen may indicate
its presence.
- possibly- cranial nerves V-VII alligned with the fenestra pseudorotunda at
the basicranium/neurocranium boundary in a line (Headden, pers. comm.)
I'll need to look at Erlikosaurus', Chirostenotes' and Conchoraptor's
braincase sometime.
- two pairs of cervical pleurocoels (Makovicky and Sues, 1998)
True in Microvenator, Chirostenotes, oviraptorids, the El Brete
caenagnathoid and a Kazakhstan therizinosauroid.  Only one pleurocoel is
preserved in Alxasaurus.  Nomingia lacks this trait.  Some tyrannosaurid
vertebrae and Utahraptor have double pleurocoels.
- ventral sulcus on cervical centra flanked by ventrolaterally directed
ridges (Frankfurt and Chiappe, 1999)
Present in the Quarry 9 enigmosaur, Thecocoelurus, therizinosauroids,
Chirostenotes and the El Brete caenagnathoid.
- cervical prezygopophyses separated by a U-shaped space (Frankfurt and
Chiappe, 1999)
Present in therizinosauroids, Microvenator, oviraptorids and the El Brete
caenagnathoid.
- caudal vertebrae decrease in length posteriorly (Sues, 1997)
True for Alxasaurus, Neimongosaurus, Caudipteryx, Nomingia, Microvenator,
oviraptorids and probably Chirostenotes.
- maybe - mid chevrons elongate and gently curved (Holtz, 2000)
Would be a reversal if true, and sounds plausible considering the tails of
Alxasaurus and Ingenia.  I need to scrutinize it further though.
- possibly- ulnar facet of humerus expanded, merges with entepicondyle
(Russell and Dong, 1994)
I still haven't examined this character.
- possibly- humeral entepicondyle prominent (Holtz, 2000
Apparently not the same as the above character, as Holtz uses both.  Sounds
related at least though.
- possibly- paired manal ungual lateral grooves do not converge (Headden
pers. comm.)
I only see a single lateral groove in enigmosaurs.  Maybe the other
"non-convergant" groove is hiding....
- pubic foot expanded anteriorly (Makovicky and Sues, 1998)
True in Segnosaurus, Enigmosaurus, Nanshiungosaurus, Caudipteryx, Nomingia,
Microvenator, Chirostenotes and oviraptorids.  Also seen in Achillobator.
- possibly- pedal unguals III and IV vertically oval in section (Holtz,
2000)
Uh, maybe.  This would be extremely difficult to find in the literature.

That's fourteen definite characters, plus at least six possible ones.  Not
including others that I find as my matrix is revised (largely postcranial).
This seems like pretty good evidence to me.  Of course, the real test is
whether they outweigh Sereno's seven (plus five possible) characters keeping
segnosaurs out of the oviraptorosaur + paravian clade, as well as how they
interact with all the other characters that are present in my analysis that
will no doubt affect things.  A priori conclusions are not good practice,
but Enigmosauria is looking pretty safe to me.

Mickey Mortimer