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Re: Terror of the terrible Theropods! :)



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
http://www.cmnh.org/fun/dinosaur-archive/2000Sep/msg00191.html
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)
 
http://www.cmnh.org/fun/dinosaur-archive/2000Sep/msg00159.html
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