New Monolophosaurus paper

[Tim Williams <tijawi@yahoo.com>]

Also in Geological Magazine...



Zhao X.-J., Benson, R.B.J., Brusatte, S.L., and Currie, P.J. The postcranial 
skeleton of _Monolophosaurus jiangi_ (Dinosauria: Theropoda) from the Middle 
Jurassic of Xinjiang, China, and a review of Middle Jurassic Chinese theropods. 
Geological Magazine doi:10.1017/S0016756809990240


Abstract: "The Middle Jurassic was a critical time in the evolution of theropod 
dinosaurs, highlighted by the origination and radiation of the large-bodied and 
morphologically diverse Tetanurae.  Middle Jurassic tetanurans are rare but 
have been described from Europe, South America and China.  In particular, China 
has yielded a number of potential basal tetanurans, but these have received 
little detailed treatment in the literature.  Here we redescribe the 
postcranial skeleton of one of the most complete Chinese Middle Jurassic 
theropods, _Monolophosaurus_. Several features confirm the tetanuran affinities 
of _Monolophosaurus_, but the possession of âprimitiveâ traits such as a 
double-faceted pubic peduncle of the ilium and a hood-like supracetabular crest 
suggest a basal position within Tetanurae.  This conflicts with most published 
cladistic analyses that place _Monolophosaurus_ in a more derived position 
within Allosauroidea.  We review the Middle
 Jurassic record of Chinese theropods and compare _Monolophosaurus_ to other 
Middle Jurassic theropods globally. These comparisons suggest that 
_Monolophosaurus_ and _Chuandongocoelurus_ formed an endemic theropod clade 
limited to the Middle Jurassic of Asia. Other Middle Jurassic Chinese theropods 
deserve further study."


The last sentence in the Abstract is an understatement.  The affinities of most 
Middle Jurassic Chinese theropods taxa still remain uncertain, in a large part 
due to the inadequacies of the original descriptions: _Xuanhanosaurus_, 
_Gasosaurus_, _Kaijiangosaurus_, _"Szechuanosaurus" xigongensis_.  

_Chuandongocoelurus_ might be based on material from more than one taxon, with 
the holotype (hindlimb and pelvic material) representing a smaller individual 
than the referred vertebrae.  This isn't the first time this idea has been 
raised, and more work on this taxon is apparently in progress.  
_Monolophosaurus_ and _Chuandongocoelurus_ share ilia of similar morphology, 
and a "new phylogenetic analysis focusing on basal tetanuran relationships 
(Benson, 2008c,d, and in press)... [finds that] _Chuandongocoelurus_ and 
_Monolophosaurus_ form a clade within Megalosauroidea (Spinosauroidea of some 
authors) outside Megalosauridae and Spinosauridae."

Thus - and no doubt in line with the re-emergence of _Megalosaurus_ as a valid 
genus - the name Megalosauroidea is used in place of Spinosauroidea.  Although 
AFAIK Megalosauroidea has yet to be defined.  Under ICZN rules, Megalosauroidea 
would certainly have priority over Spinosauroidea (and Torvosauroidea). 


Cheers

Tim