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Oliver Rauhut was recently kind enough to send me a
copy of his thesis (written in 2000, not 1999 like I cited earlier). It
contains lots of new information I believe would be of interest to the
list. The topic of the thesis is phylogenetic relationships of basal
theropods, although derived taxa are included. An analysis was performed
that resulted in 5544 trees of 652 steps each that had a consensus
of-
_____Euparkeria
|_____Marasuchus
|_____Ornithischia
|_____Sauropodomorpha
|_____Eoraptor
|_____Staurkiosaurus
|
|_Herrerasaurus
|______Segisaurus
|
|_Syntarsus
| |_Coelophysis
| |_Gojirasaurus
| |_Shuvosaurus
| |__Liliensternus
liliensterni
| |__Liliensternus
airelensis
|________Dilophosaurus
|________Ceratosaurus
|
|__Elaphrosaurus
|
|_Abelisauridae (including Noasaurus)
|_________Piatnitzkysaurus
|_________"Szechuanosaurus" zigongensis
|___________Magnosaurus (including Eustreptospondylus)
| |_______Monolophosaurus
| |_______Poekilopleuron
| |_______Torvosaurus
| |
|____Chilantaisaurus
| |
|___Spinosauridae (Baryonychidae is used)
| |________Afrovenator
| |_____Allosaurus
|
|_____Sinraptoridae
|
|___Neovenator
|
|__Carcharodontosauridae (including Acrocanthosaurus)
|____________Proceratosaurus
|____________Coelurus
|
|____Sinosauropteryx
|
|___Compsognathus
|
|__Santana compsognathid
|_____________Stokesosaurus
|
|___Tyrannosauridae
|_____________Ornitholestes
|____________Deltadromeus
|
|___Ornithomimosauria
|_____________Bagaraatan
|_____________Segnosauria (Therizinosauroidea is used)
|
|______Caudipteryx
|
|_____Microvenator
|
|_____Caenagnathoidea (Oviraptorosauria is used)
|
|_____Avimimus
|______________Troodontidae
| |___Dromaeosauridae (including
Sinornithosaurus)
|_________Unenlagia
|_____Aves (including Rahonavis)
As you can see, Ceratosauria as usually constructed
is paraphyletic, which was a main point of the paper. Another major
difference from other recent analyses is the inclusion of megalosaurs and
spinosaurs in the Carnosauria. I will discuss some new information or
different viewpoints below. One great thing about this paper is that
Rauhut examined most specimens personally to determine the presence or
absence of characters. Unfortunately, I feel Rauhut often makes taxa
nomina dubia without sufficient reason and makes many species metataxa,
which I feel is inappropriate. I'll defend a few of these cases below, but
many others I disagree with require further study. However, even taking
these issues into account, the overall quality of the paper is
excellent.
Eoraptor has palatal teeth, but the claim of such
structures in Massospondylus (Attridge et al., 1985) is incorrect, being the
result of fish teeth washing onto the palate before burial (Sereno pers. comm.
to Rauhut 1997). Although Eoraptor and herrerasaurids are placed as
theropods in the consensus tree, most of the synapomorphies relate to predatory
habits and there are many reversals needed, which makes this conclusion
tenuous.
The brevis shelf of Caseosaurus is medially
expanded as in some crurotarsans, not laterally expanded like Herrerasaurus and
most dinosaurs. In addition, the acetabulum is incomplete, so its extent
cannot be judged. Thus, Rauhut claims it cannot be shown to be
dinosaurian.
The dorsals of Chindesaurus are not tall and
craniocaudally short like herrerasaurids. The ilium originally referred to
this species is now the holotype of Caseosaurus, so ilial herrerasaurid
synapomorphies cannot be determined. Thus, no herrerasaurid synapomorphies
are present in the holotype. Also, there is uncertain mixing of the
holotype material with a partial Chatterjeea skeleton in the same pocket.
Because of these facts, Rauhut refers Chindesaurus to Archosauria indet., but I
believe reexamination of the material will show more precise
relations.
Rauhut says that the elongate mandibular symphysis
of Alwalkeria is unlike theropods, but similar to some
crurotarsans. The paraphyletic traditional Ceratosauria is also
seen in Carrano and Sampson 1999. The characters traditionally used to
support the Ceratosauria are rather problematic-
- strongly backturned and triangular dorsal
transverse processes. Triangular diapophyses are found in many tetanurines
and the degree of backturning varies within the dorsal column.
- two pairs of cervical pleurocoels. Because there
are no known non-neotheropods with pleurocoels, whether having one or two pairs
of pleurocoels is the primitive state cannot be determined. This study
suggests having two pairs is primitive. This is also suggested by avian
embryological data (Britt, 1993). Liliensternus liliensterni only has a
single pair.
- pubic fenestra. Not present in Liliensternus,
Ceratosaurus, Elaphrosaurus or abelisaurids. Possibly synapomorphic for a
coelophysoid subgroup.
- synsacrum. Varies ontogenetically.
- pelvis fused. Varies ontogenetically and is only
partially developed in the old adult Elaphrosaurus holotype.
- trochanteric shelf. Present only in robust
individuals and known in Herrerasaurus and basal dinosauriformes.
- sulcus at base of crista tibiofibularis. The
characteristic oblique sulcus is only present in Syntarsus. Absent in
Segisaurus, Coelophysis, Liliensternus. A longitudinal sulcus like
that found in tetanurines is known in Dilophosaurus, Ceratosaurus, Elaphrosaurus
and abelisaurids.
- astragalocalcaneum fused to tibia.
Ontogenetically variable and absent in the old adult Elaphrosaurus
holotype.
- ascending process of astragalus overlapped by
fibula. Present in Syntarsus, but not Liliensternus, Dilophosaurus,
Ceratosaurus or abelisaurids
- distal tarsals fused to metatarsus.
Ontogenetically variable and absent in the old adult Elaphrosaurus
holotype.
The neoceratosaur-tetanurine clade is supported by
fifteen synapomorphies- presence of a promaxillary foramen in the maxillary;
ascending process of the maxillary offset from the anterior margin of the
maxillary body; prefrontal displaced medio-posteriorly; ventral margin of the
bases of the paroccipital processes situated at, or below the mid-height of the
occipital condyle; tooth row ends below the anterior margin of the orbit;
retroarticular process of the mandible broad and attachment for the M. depressor
mandibulae developed as a posteriorly placed groove; pleurocoels present in
axis; cervical pleurocoels developed as foramina that pierce the vertebral body;
cervical epipophyses strongly overhang the postzygapophyses; iliac blade
expanded ventrally anteriorly; pubic apron has a medial opening distally; lesser
trochanter broadened and wing-like; distal end of the femur well rounded; distal
articular surface of the tibia broadly triangular in outline; tibial facet
present on the calcaneum. It has a bootstrap of 90% and it takes 13 more
steps to make the traditional Ceratosauria monophyletic.
Coelophysoidea as traditionally used (Coelophysidae
+ Dilophosaurus) is also shown to be paraphyletic. Four synapomorphies
have been suggested for this clade-
- subnarial gap. True, but the structure is
different, that of Dilophosaurus being closer to that of
spinosaurids.
- no axial diapophyses. Also in Herrerasaurus
and prosauropods, probably symplesiomorphic.
- reduced axial parapophyses. Also in
Herrerasaurus and prosauropods, probably symplesiomorphic.
- no axial pleurocoels. This is obviously
plesiomorphic, seen in Herrerasaurus, Eoraptor, sauropodomorphs,
etc..
Seven additional synapomorphies were found
(premaxillary body in front of external nares longer than body below the nares,
and angle between anterior margin of the premaxilla and alveolar margin less
than 70 degrees; presence of a constriction between the articulated
premaxillaries and maxillaries; the lateral rims of the nasals are pronounced
and form raised edges; no contact between the squamosal and quadratojugal;
presence of enlarged, fang-like teeth in the anterior part of the dentaries;
posterior dorsal vertebrae considerably elongated; articular facet of the pubic
peduncle of the ilium subdivided into an anterior part that faces anteriorly,
and a posterior part that faces ventrally), but were overridden by nine
characters grouping Dilophosaurus with ceratosaurs sensu stricto and
tetanurines- presence of a promaxillary foramen in the maxillary; prefrontal
displaced posteriorly; tooth row ends at the anterior margin of the orbit;
cervical pleurocoels developed as foramina that lead into the interior of the
vertebral body; axial and cervical epipophyses strongly pronounced and
overhanging the postzygapophyses; anterior articular facet of anterior cervicals
wider than high; presence of a medial opening in the pubic apron distally;
presence of a deep groove in the medial side of the proximal end of the fibula;
Mt V flattened transversely and flexed anteriorly in its distal part. Only
three steps are needed to make a traditional Coelophysoidea, but if Shuvosaurus
is excluded it is just as parsimonious as the tree presented above. This
is because the latter taxon lacks a few of the proposed traditional coelophysoid
characters- it lacks a subnarial gap and a constriction between the
premaxillaries and maxillaries, the lateral margins of the nasals are not
raised, and the squamosal contacts the quadratojugal.
Procompsognathus grouped with the coelophysoids in
preliminary analyses, but was removed as it contained no unique combination of
characters.
Shuvosaurus is a coelophysid based on two
characters shared with Syntarsus- forked posterior end of the premaxilla,
considerably elongated basisphenoid.
Elaphrosaurus is diagnosed as having a very wide
scapular blade (broader than height of vertebral column). The
extremely wide scapular blade is yet another character supporting a
Chuandongocoelurus + Elaphrosaurus clade, although Chuandongocoelurus' is
only 75% as high as the vertebral column.
Noasaurus is included in the Abelisauridae because
it shares several characters with the family (short high antorbital part of
maxilla, cervical epipophyses hypertrophied and higher than neural spines.
Also, no cladistic analysis has been done on abelisauroids, so it is possible
Noasaurus is more closely related to some abelisaurids than others. I
think the reduced second metatarsal is similar to Masiakasaurus and
Velocisaurus, and the sickle claw is similar to Ligabueino. Pedes are
poorly known in abelisaurids, so these characters may not mean much.
However, Ilokelesia is thought by Headden to be a carnotaurine and lacks a
sickle claw. Also, Noasaurus lacks the fused quadrate and quadratojugal
seen in Abelisaurus and Carnotaurus, though apparently not Majungatholus.
So I think that it is premature to place Noasaurus in the Abelisauridae, but
agree that more work needs to be done in this area.
Ligabueino and Velocisaurus scored identically to
Elaphrosaurus, so were not included. This is more evidence for a clade
containing these genera, probably also including Noasaurus, Masiakasaurus and
Laevisuchus.
He suggests Genusaurus is closer to Carnotaurus
than Majungatholus, based on the straight dorsal ilial margin and very long
vertically oriented ischial peduncle. Also, Rauhut thinks Indosaurus is
more similar to allosauroids and that the broad horizontal plate separating the
supratemporal fenestrae makes this taxon different from abelisaurids.
Novas and Bandyopadhyay (1999) disagree. Interestingly, Indosaurus,
Indosuchus and Compsosuchus were first described by Huene and Matley in 1932
(pg. 237), not 1933. So their entries should be changed in George's
Dinosaur Genera List and other places.
The Carnosauria clade, containing both traditional
carnosaurs, as well as megalosaurs and spinosaurs, is supported by only three
synapomorphies- ascending process of the maxillary offset from the anterior rim
of the maxillary body and anterior projection of the maxillary body longer than
high; cervical vertebrae strongly opisthocoelous; metacarpal I very stout and
approximately as broad as long. Arranging the taxa into spinosauroids and
allosauroids as in Sereno (1999) requires three more steps. Forcing the
topology of Holtz (2000) (with spinosaurids, Eustreptospondylus, Torvosaurus,
Piatnitzkysaurus and Afrovenator successively closer to avetheropods, and
Monolophosaurus and allosauroids in a monophyletic Carnosauria)
requires eleven more steps.
Rauhut uses Baryonychidae in place of Spinosauridae
because of uncertainty regarding the association of Spinosaurus' holotype.
The cervical vertebra has a low neural spine, which Rauhut considers too
different from the high-spined dorsals to belong to the same taxon.
Furthermore, he claims the dorsal vertebrae lack the strong pneumatization and
laminae of Baryonyx and Suchomimus and are comparable to allosauroids except for
the tall spines. As tall neural spines are known in Acrocanthosaurus, he
suggests the dorsals may belong to a carcharodontosaurid. The
proximal caudal described by Stromer as possibly being too large for the
holotype is said to resemble ornithischian caudals more. Quite an
interesting problem, as the name Spinosaurus would no doubt stay with whatever
taxon the dorsals belong to. I've lost my figures to Stromer 1915 and
haven't examined spinosaurids closely in any case, but wouldn't it be odd if
Spinosaurus turned out to be an allosauroid? Jurassic Park never had a
chance :-) . Additionally, Spinosaurus marocannus was originally
distinguished from S. aegyptiacus by its elongate cervical vertebra.
However, it is longer because it is a more anterior vertebra than the
type of S. aegyptiacus, making the validity of S.
marocannus dubious.
Eustreptospondylus is made a junior synonym of
Magnosaurus, to form the new combination Magnosaurus oxoniensis. This is
because they share the following characters- slight dorsoventral and transverse
expansion of anterior dentary; significantly enlarged third dentary tooth;
shallow longitudinal groove with rectangular cross section in dentary.
Also, the remains of both are almost indistinguishable, differing only in slight
differences in the proximal extent of the pubic apron. I think this sounds
probable, but cannot comment due to the lack of proper references on
either.
Rauhut refers to Becklespinax as Altispinax
altispinax, as Huene proposed the name Altispinax for the vertebrae, not the
indeterminate tooth of Megalosaurus dunkeri. Thus, Becklespinax is a
junior synonym, though altispinax is the first species name available.
Everyone change your lists. :-)
"Szechuanosaurus" zigongensis is shown to be more
basal than carnosaurs due to the platycoelous cervicals, non-pleurocoelous
dorsals and other characters. It is very similar to Xuanhanosaurus in all
areas except humeral morphology.
Xuanhanosaurus' description (Dong, 1984) and
reexamination (Molnar, 1990) are incorrect in a couple points. The sternum
is actually an impression of part of the right coracoid. The carpal and
phalangeal joints do not differ from the typical theropod pattern, with highly
flexible digits and a somewhat opposable pollex. The arm was actually
rather short in comparison to the body, so there is no evidence for quadrupedal
motion. Xuanhanosaurus was not included in the final analysis to limit the
amount of MPT's, but grouped as either a basal tetanurine or a basal
carnosaur.
Although not included in the analysis, the distal
tibia outline and proximal extent of the anterior trochantor show Erectopus is a
basal tetanurine, not an abelisaurid as has been recently proposed.
Rauhut notes that Yangchuanosaurus shangyouensis,
Y. magnus, Sinraptor dongi and S. hepingensis are all nearly identical in
morphology. Additionally, all but S. dongi are from the same
formation. He suggests they may be synonymous, which would make
Yangchuanosaurus shangyouensis the correct name. However, he has not
examined them firsthand, so provisionally keeps them separate.
Metriacanthosaurus was not included because it
scored identically to sinraptorids.
Rauhut argues against the assignment of
Siamotyrannus to the Tyrannosauroidea. He states that the structure in the
figure is not a medioventral shelf on the ilium, that other theropods have
vertical lateral ilial ridges and proximolateral ischial scars, and that the
pubic foot is broken posteriorly, so its length cannot be determined.
However, he fails to mention the narrow second and third sacral centra,
well-marked insertion of the transverse process of sacral 1 on the ilium and
other minor characters cited by Buffetaut et al.. Still, I am inclined to
believe Rauhut and Pharris that Siamotyrannus is more likely to be a
carnosaur. It grouped with allosauroids in the preliminary analysis,
before it was excluded to limit the number of MPT's.
The presence of a (Coelurus + Compsognathidae)
clade is unique and supported by only two synapomorphies- cervical epipophyses
not overhanging the postzygapophyses; posterior dorsal neural spines lower than
long. The same can be said of the (Deltadromeus + Ornithomimosauria)
clade- straight humerus in lateral view; presence of a deep and wide groove on
the medial side of the proximal end of the fibula. Only one step is
necessary to make Deltadromeus a basal coelurosaur. Enforcing the
coelurosaurian phylogeny of Holtz (2000) adds 31 steps. Sereno's (1999)
phylogeny takes 26 more steps. My most recent phylogeny takes 20 more
steps.
Rauhut notes Deltadromeus has a well
developed anteromedial ridge on the distal femur. This is more
similar to ceratosaurs than coelurosaurs. Additionally, the
anteroposteriorly long proximal caudal neural spines, reduced fourth metatarsal
and proximally unreduced third metatarsal have me thinking of Elaphrosaurus
after all the time I spent looking at the latter genus for "Details on
Chuandongocoelurus".
Rauhut assigned Bahariasaurus to the
Carcharodontosauridae in 1995 based on characters of referred material.
The holotype is said to lack carcharodontosaurid synapomorphies and be very
close (if not identical) to Deltadromeus.
Rauhut notes Albertosaurus megagracilis is a nomen
nudum, as Paul did not illustrate it, cites the wrong reference and gives no
formal diagnosis. Of course, it's just a subadult Tyrannosaurus rex, so it
doesn't matter that much.
"Chilantaisaurus" maortuensis came out as a basal
coelurosaur before it was removed to limit the number of MPT's.
The absence of transverse processes in
Compsognathus is no longer certain. There is a large crack running through
the caudal series which makes it impossible to determine their presence.
Rauhut also reinterprets the manus so that mcI of Ostrom equals mcII, mcII =
mcIII, mcIII = mcIV, I-1 = II-1, II-1 = I-1, ungual I = ungual III.
This differs from the suggested reconstruction by Gauthier and Gishlick (2000),
where mcI = I-1, mcII = mcII, mcIII = mcIII and a "mystery element" of Ostrom is
really mcI. In any case, the pubic foot is actually much longer than
reconstructed by Ostrom, being more similar to the C. "corallestris"
specimen.
Rauhut still coded AMNH 587 (the referred manus) as
Ornitholestes, while it is now known to be Coelurus, which may have had an
adverse affect on the analysis. Ornitholestes does not have a nasal horn
(contra Paul, 1988), as "the apparent upward flexure of the posterior border of
the external nares on the left side of the skull is caused by a break and
subsequent ventral displacement of the ascending process of the maxilla and the
nasals."
Rauhut notes that there are no comparable elements
in Piveteausaurus and Proceratosaurus, so their referral to the same family and
genus by Paul (1988) is unfounded. Piveteausaurus differs quite a bit from
Ornitholestes, to which it can be compared.
Timimus is said to be indistinguishable from other
coelurosaurs, but see http://www.cmnh.org/fun/dinosaur-archive/2001Mar/msg00681.html for
why this is untrue. Currie (pers. comm. to Rauhut 1998) thinks
Dromiceiomimus may be synonymous with Ornithomimus.
Rauhut uses "Nanshiungosaurus" bohlini, as I
suggested in my "Details on Nanshiungosaurus bohlini" post. He bases this
on temporal and unspecified morphological differences.
He says that the presence of a posterior ulnar
ridge on Avimimus is uncertain, as the proximal end doesn't fit into the proper
condyle of the humerus. Nevertheless, Watabe et al. (2000) report new
remains show the ulna does indeed have the ridge.
There has been a rumor on the list recently that
Koparion is not troodontid. This seems to stem from a statement made by
Harris in 1997 that Chure (pers. comm.) no longer believes it belongs in this
family. Rauhut says that because constricted roots are known in
non-troodontid theropods and Koparion is similar to Compsognathus, it may be a
compsognathid. However, he fails to note that other troodontid characters
are present in Koparion, including an apex formed by the most distal posterior
serration, blood pits between serrations, enlarged serrations and posterior
serrations curved apically. At least the last two characters are not found
in Compsognathus. Thus, I still believe Koparion is a
troodontid.
The distal ends of Sinornithoides' pubes are broken
off, so it is impossible to determine if there was a pubic foot. A pubis
referred to Troodon (MOR 553S 8.3.9.387) has a pubic foot, but was not
associated with Troodon material and has a larger anterior foot and a cranially
concave shaft. Sounds like Chirostenotes to me.
Rauhut argues Archaeornithoides is Archosauria
incertae sedis, as unserrated teeth with basal constrictions and no interdental
plates are known for both crocodilians and avians. However, he does not
take the subsidary palatal fenestra into account, which is a coelurosaurian
synapomorphy. I recommend it remain in the Maniraptoriformes and possibly
in the Troodontidae (as suggested by Currie, 2000).
Rauhut uses a very loose definition of
Dromaeosauridae, including the avian Hulsanpes, as well as the more basal
deinonychosaur Sinornithosaurus. This may have affected the results.
In addition to the definite dromaeosaurids, Adasaurus, Megaraptor and
Utahraptor were also included. The cervicodorsal of Variraptor is referred
to the Oviraptorosauria because it has two pairs of pleurocoels. As
Achillobator also has this feature though, I feel the referral is
inappropriate. He refers the taxon to Coelurosauria indet.. The
quadrangular posterior articular surface of the last sacral centrum is only
known in troodontids, dromaeosaurids, Rahonavis and Archaeopteryx. The
pneumatic posterior dorsals and anterior sacrals, and five sacral vertebrae are
unlike troodontids. Thus, Variraptor is a eumaniraptoran. Further
analysis is difficult, pending a stable eumaniraptoran phylogeny and description
of more eumaniraptoran sacra.
If anyone has any questions, feel free to ask
them. Now to perform Ken's experiment with segnosaurs in this
analysis.....
Mickey
Mortimer |