[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
New Monolophosaurus paper
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).