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Fam Jansma wrote-
> Could anyone help me with some info or
pictures of the following genera?
> - Chilantaisaurus (both C. maortuensis and
C. t.)
C. maortuensis is now known as "Alashansaurus"
maortuensis. It is known from a maxilla, quadrates, posterior section of
skull, axis and six caudal vertebae. Both Rauhut (2000) and
Chure (2001) classify it as a coelurosaur. Characters
include- fused/absent interdental plates; no promaxillary fenestra; unfused
frontals; transversely straight nasofrontal suture; sagittal crest on frontals
and parietals; no quadrate-quadratojugal foramen; single quadrate head; no
helical groove on quadrate; highly pneumatized braincase; parasphenoid not
inflated; ventrally projecting paroccipital processes; occipital condyle with
constricted neck. Where exactly it goes is not known, but perhaps my
analysis will shed some light.
C. tashuikouensis is the holotype and is known from a humerus,
first manual ungual, fragmentary ilium, femora, fibula and metatarsus. It
has been allied with basal tetanuraens, allosaurids segnosaurs and
tyrannosaurids. It was placed in the Spinosauroidea as the sister group of
spinosaurids by Rauhut (2000) based on- humerus straight in lateral view;
bluntly rounded vertical ridge on the antero-medial side of the distal end of
the tibia. Sereno et al. (1994) classifies Chilantaisaurus as a
torvosauroid (Afrovenator, Eustreptospondylus, Torvosaurus, spinosaurids) and
renamed the clade Spinosauroidea for their 1996 and 2000 papers. Of the
torvosauroid synapomorphies listed by Sereno et al. (1994, 1996), none can be
determined in C. tashuikouensis as they are all cranial. The torvosaurid +
spinosaurid subgroup is diagnosed by "manual ungual I elongate (three times
height of proximal articular end)", which is present in C. tashuikouensis.
Also, in 2000, Sereno added deltopectoral crest more than 45% of humeral length,
which is almost true of C. tashuikouensis. Although these two characters
are present in Chilantaisaurus, it is debatable if they imply a relationship to
torvosauroid/spinosauroid taxa. If Sereno's manual ungual length is along
the curve (as it must be for Baryonyx to exhibit the trait, so I assume it's
implied), Chilantaisaurus has a ratio of 3.17, while Baryonyx has a ratio of 3.2
and Torvosaurus has a ratio of 3.4. Neither Herrerasaurus, coelophysoids,
Dilophosaurus, Afrovenator or Allosaurus show these proportions. However,
several basal coelurosaurs have the derived condition (Nqwebasaurus,
Dryptosaurus, Sinosauropteryx, most ornithomimids), although others don't
(Compsognathus, Scipionyx, tyrannosaurids). This shows the character
distribution to be more complex than previouly thought. Chilantaisaurus's
deltopectoral crest extends 44% of humeral length. This compares to 37 in
Allosaurus, 40 in Liliensternus and Dilophosaurus, 41 in Ceratosaurus, 42 in
Segisaurus and Elaphrosaurus "philtippettorum", 43 in Eustreptospondylus and
Baryonyx, 46 in Torvosaurus and 51 in Carnotaurus. Thus, if the
synapomorphic percentage is moved from over 45 to over 42, the character still
holds (allowing convergence with abelisaurs), but I don't think a one percent
difference from other theropods means much. Because of this extremely
minor difference in length between torvosauroids and other theropods, I wouldn't
trust this character. Still, it seems to be best placed as a spinosauroid
for now.
> - skull remains of
Adasaurus
Specifically-
"There are skull remains, but all that is said regarding them
is that they "bear a great similarity to other members of the subfamily,
obviating the need to repeat general skull characters" (Barsbold 1983).
The subfamily referred to is the Dromaeosaurinae (with Dromaeosaurus, Adasaurus
and Deinonychus), separated from the Velociraptorinae (with Velociraptor) by the
high, relatively large skull. From this, we may assume that Adasaurus had
a higher skull than Velociraptor, more similar to Dromaeosaurus
and
Deinonychus." Also, Xu et al. (2002) code it as having both premaxillary and
maxillary teeth.
> - skeletal remains of Santaraptor (I have
this nagging suspicion, based on the model of it's skeleton,
> that it could very well be a
Oviraptorid based on the overall similarities of the pelvis)
It's not an oviraptorid, much too primitive. Note the
elongated mid-caudals, wing-like anterior trochantor that ends far below the
greater trochantor and proximally placed obturator process. Something
more akin to Ornitholestes.
Mickey Mortimer
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