|
With all of this discussion going around, just what
characters support the Enigmosauria? The following have been presented in
the past as enigmosaur synapomorphies (authors cited), or might come out that
way in my analysis.
- premaxilla with broad palatal shelf (Sues,
1997)
Present in Erlikosaurus, oviraptorids and probably
Chirostenotes, but also in tyrannosaurids, ornithomimosaurs, troodontids,
Velociraptor, birds, etc..
- 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.
- rim of antorbital fossa well developed (Sues,
1997)
Found in Erlikosaurus, Chirostenotes and some
oviraptorids. Also in some ornithomimosaurs and perhaps some troodontids,
probably absent in Caudipteryx.
- posterior section of premaxilla toothless (modified from Sues, 1997) Present in Erlikosaurus, Caudipteryx
and oviraptorids, also in derived ornithomimosaurs and some
pygostylians.
- maxillary fenestra absent (Sues,
1997)
Seen in Erlikosaurus and
Chirostenotes, not in Caudipteryx and oviraptorids. Also in some
pygostylians and possibly Gallimimus.
- 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). - nasal (anterior
tip to middle suture point) divided by frontal (middle suture point to posterior
tip) <135%
Found in Caudipteryx and Erlikosaurus, but not
oviraptorids. Avians also have this (as do Scipionyx, Bambiraptor and NGMC
91, but this may be ontogenetic).
- ectopterygoid
lateral to palatine (no ectopterygoid-palatine fenestra) (Sues,
1997)
Seen in Erlikosaurus and oviraptorids.
- triradiate palatine
Present in Erlikosaurus and oviraptorids, but not
in Chirostenotes. Also in Shuvuuia and avians.
- lateral depression in middle ear region of
braincase (Sues, 1997)
Present in Erlikosaurus and Chirostenotes, but probably not in oviraptorids. Also present in troodontids and perhaps mononykines and Archaeopteryx. - reduced basipterygoid processes (Russell and
Dong, 1994)
True in Erlikosaurus, Nothronychus, Chirostenotes and oviraptorids. - vomers extend posteriorly to basicranium (Russell
and Dong, 1994)
This is true of Erlikosaurus, but not 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. - dentary strongly forked posteriorly (Rauhut,
2000)
True in Caudipteryx, Microvenator, Chirostenotes
and oviraptorids, but not in Erlikosaurus or Segnosaurus. An
oviraptorosaurian synapomorphy also seen in Confuciusornis.
- 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. Past here, I haven't closely examined the
characters for my new analysis, so the conclusions aren't as
certain.
- premaxilla long and pointed, with long nasal
process (Holtz, 2000)
I wouldn't call Erlikosaurus' or Caudipteryx's
premaxilla especially long or pointed (certainly not as much as Compsognathus's,
basal birds or Shuvuuia's), more comparable to ornithomimosaurs and
troodontids. Oviraptorids have very short premaxillae, though
pointed. The nasal processes of Caudipteryx and oviraptorids seem to be of
normal length, though Erlikosaurus does have a more elongate one (probably due
to the long naris). These characters will need to be separated and
quantified.
- premaxillary symphysis U-shaped (Norell et al.,
2001)
Present in Erlikosaurus and oviraptorids, but
tyrannosaurids, ornithomimosaurs and troodontids have this too.
- maxillary process of premaxilla moderately long,
premaxilla participates broadly in external naris (Holtz, 2000)
The primitive condition, not present in
Erlikosaurus.
- lacrimal not exposed on skull roof (Holtz,
2000)
Unknown in Erlikosaurus due to displacement, absent
in oviraptorids (Elzanowski, 1976).
- shaft of lachrymal bowed rostrally (Headden,
pers. comm.)
Although some oviraptorids have this condition, I
don't think Caudipteryx or Erlikosaurus could be described that
way. - frontal very broadly exposed on skull roof,
postorbital ramus does not project abruptly laterally from orbital margin
(Holtz, 2000)
The first part sounds like a symplesiomorphic
coelurosaurian trait, the second primitive compared to troodontids and
deinonychosaurs.
- vomer limited to rostral region (Holtz,
2000)
Isn't this supposed to be the other way around, as
in "vomers extend posteriorly to basicranium"? Certainly untrue of
Erlikosaurus.
- ectopterygoid does not contact jugal (Headden,
pers. comm.)
Erlikosaurus has a portion of the ectopterygoid
contacting the medial surface of the jugal, though I'm unsure if this is due to
displacement.
- 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. - occipital region deflected ventrally (Sues,
1997)
Present in ornithomimosaurs and troodontids, but I
don't think Erlikosaurus or oviraptorids could be described this
way.
- no surangular foramen (Norell et al.,
2001)
The character I'm on at present in my analysis
revision. The surangular foramen is present in Erlikosaurus at
least, seems to be an oviraptorosaurian character at best.
- no posterolateral surangular ridge (Headden,
pers. comm.)
True in Erlikosaurus, Caudipteryx, Chirostenotes
and oviraptorids. Also in Compsognathus, ornithomimids, Shuvuuia,
troodontids, Archaeopteryx and other birds. - 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. - peduncular foramina on cervicals (Frankfurt and
Chiappe, 1999)
Present in the Quarry 9 enigmosaur, therizinosauroids, Chirostenotes and the El Brete caenagnathoid. Also in Coelurus and Deinonychus at least. - 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. - cervical centra more than 150% longer than high
(Headden, pers. comm.)
As in Sinosauropteryx, Coelurus, ornithomimosaurs,
troodontids and alvarezsaurids. As these are directly below and above
enigmosaurs phylogenetically, it seems to be plesiomorphic for the
clade.
- cervical ribs less than twice centrum length and
broad (Holtz, 2000)
Haven't looked that closely at this character yet,
but it seems to be present in ornithomimosaurs, Sinornithoides and Deinonychus
too for instance.
- all dorsal vertebrae pleurocoelous (Makovicky and Sues, 1998) Present in Beipiaosaurus, "Nanshiungosaurus" bohlini, Nomingia, Microvenator and oviraptorids. Alxasaurus and Nanshiungosaurus brevispinus lack dorsal pleurocoels, while Caudipteryx lacks them at least posteriorly. However, this is also seen in tyrannosaurids and eumaniraptorans (except Velociraptor). - dorsal spine tables absent (Holtz,
2000)
Plesiomorphic of course, but the absence of spine
tables in ornithomimosaurs, Coelurus, Ornitholestes and Scipionyx would suggest
it is primarily primitive in enigmosaurs, not secondarily.
- all sacrals pleurocoelous (Headden, pers.
comm.)
True in Neimongosaurus, Chirostenotes and
oviraptorids. Alxasaurus only has a possible pleurocoel in sacral 1, the
others being non-pleurocoelous. Caudipteryx lacks them (Zhang et al.,
2001). Perhaps also true in Eotyrannus.
- caudal vertebrae decrease in length posteriorly (Sues, 1997) True for Alxasaurus, Neimongosaurus, Caudipteryx, Nomingia, Microvenator, oviraptorids and probably Chirostenotes. - no caudal transition point (Holtz,
2000)
True in oviraptorids and probably Microvenator and
Chirostenotes. Alxasaurus, Caudipteryx and Nomingia have transition
points.
- caudal neural spines present past caudal 10
(Holtz, 2000)
This is primarily primitive, as seen by the similar
condition in Sinosauropteryx, tyrannosauroids, ornithomimosaurs
and Bagaraatan. Only more derived maniraptorans and Compsognathus
have the derived condition.
- distal caudal transverse processes not elongate
(Rauhut, 2000)
Present in Alxasaurus, Microvenator, Chirostenotes
and oviraptorids, absent in Neimongosaurus, Caudipteryx and Nomingia. Also
developed in Coelurus, Compsognathus, alvarezsaurids, troodontids and
avians.
- proximal chevrons elongate and rodlike (Norell et
al., 2001)
Plesiomorphy seen in ornithomimosaurs,
tyrannosaurids, compsognathids, etc..
- 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.
- distal chevrons lack cranial and caudal
projections (Holtz, 2000)
The last chevron preserved in Alxasaurus is the
fifteenth, so I don't think any distal morphology can be observed.
Nemongosaurus doesn't preserve any such chevrons, but it's never specified where
the several chrvons known originate in the tail.
- forelimb/hindlimb ratio >50% but less than
120% (Holtz, 2000)
I don't think a range of values like this is
a proper character. I measure forelimb length compared to femoral length
to reduce the affects of changes in leg length, so my values aren't strictly
comparable. Compared to femoral lengths at least, enigmosaurs are similar
to Ornitholestes, ornithomimosaurs and troodontids.
- ulnar facet of humerus expanded, merges with entepicondyle (Russell and Dong, 1994) I still haven't examined this character. - humeral entepicondyle prominent (Holtz,
2000
Apparently not the same as the above character, as Holtz uses both. Sounds related at least though. - proximodorsal lip on manual unguals (Sues, 1997) This is a highly variable character in both morphology and which unguals it forms on. Caudipteryx lacks it on unguals I and II (digit III lacks an ungual). Microvenator has it in the single ungual preserved. Caenagnathids show it on all unguals. Most oviraptorids have it on some unguals (Conchoraptor- I and II; Citipati- I, II and III; Oviraptor philoceratops- not on II at least; Ingenia- none). Alxasaurus shows it on II, but not I. Therizinosaurus on I and II, but not III. Beipiaosaurus on I, but not II. - 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.... - preacetabular process much longer than
postacetabular process (Sues, 1997)
Not any more so (and often less) than most other
maniraptorans (excluding Sinornithoides and Avimimus). I have a long list
of these values for coelurosaurs.
- preacetabular process greatly expanded dorsoventrally (Russell and Dong, 1994) True in segnosaurs, Chirostenotes and "Rinchenia". I don't feel the slight condition in Caudipteryx, Microvenator and Nomingia is that different from other theropods. Ingenia and Khaan certainly lack it. - supracetabular crest absent (Holtz,
2000)
As Alvarezsaurus, troodontids and eumaniraptorans
have it, seems best as a maniraptoran character.
- postacetabular process tapered (Russell and Dong, 1994) True in therizinosauroids, but not Beipiaosaurus, Caudipteryx, Nomingia, Chirostenotes or oviraptorids. Also found in most eumaniraptorans and troodontids, among others. - pubes cranially concave (Headden, pers.
comm.)
A deceptively complex character, due to the
difference between concavity caused by the pubic foot and that by the
shaft. I would say Segnosaurus, Enigmosaurus
and Nomingia definitely don't have it, Nanshiungosaurus and
Ingenia do, I would be hesitant about Caudipteryx and Khaan.
- pubic foot expanded anteriorly (Makovicky and Sues, 1998) True in Segnosaurus, Enigmosaurus, Nanshiungosaurus, Caudipteryx, Nomingia, Microvenator, Chirostenotes and oviraptorids. Also seen in Achillobator. - anterior trochantor cylindrical (Holtz,
2000)
Not in Beipiaosaurus, otherwise universal in
Maniraptora.
- fourth trochantor absent (Holtz,
2000)
Not true in Beipiaosaurus, Neimongosaurus,
Segnosaurus, Citipati and Ingenia, though is in Microvenator and
perhaps Nomingia.
- medial calcaneal tuber enlarged (Holtz,
2000)
This would be the process fitting into the
astragalus? The only segnosaur that the area has been described in is
Segnosaurus, where the calcaneum is said to "fit into a prominent socket on the
astragalus." Microvenator has a shallow concavity on the astragalus for
the calcaneum, while Chirostenotes' is "deeply excavated". Caudipteryx has
some sort of concavity. Oviraptorids are said to have a "protuberance",
but the extent is not described. However, Gallimimus's astragalus is also
"deeply notched" and Gorgosaurus' is concave. Other coelurosaurs are
either undescribed in the appropriate area (dromaeosaurids) or have
fused/absent calcanea (Bagarratan, alvarezsaurids, troodontids, birds).
Carnosaurs have deep interlocking complexes of pits and processes. I don't
think this character is viable, due to the lack of a distinct difference in
enigmosaurs.
- pedal unguals III and IV vertically oval in
section (Holtz, 2000)
Uh, maybe. This would be extremely difficult
to find in the literature.
So, there are the characters and
distributions. The only real way to test them would be to run a
phylogenetic analysis with them, Sereno's tyrannoraptoran and "maniraptoran"
characters, and plenty of others of course. I'm in the process of doing
this, but until then, use your own judgement and see if you think at least some
of these merit consideration.
Mickey Mortimer |