Context for *Duriavenator*: Benson's tetanuran phylogeny

[David Marjanovic <david.marjanovic@gmx.at>]

Roger Benson: A new theropod phylogeny focussing on basal tetanurans, and 
its implications for European 'megalosaurs' and Middle Jurassic dinosaur 
endemism, SVP meeting abstracts 2008, 51A

"Theropod dinosaur phylogeny has been tested by numerous cladistic analyses. 
However, areas of uncertainty remain, such as the interrelationships of 
basal, non-coelurosaurian tetanurans. A new phylogenetic dataset constructed 
to resolve basal tetanuran relationships includes 41 operational taxonomic 
units (OTUs), including 37 basal tetanurans, more than any previous 
analysis. 213 characters (22 new) were compiled based on thorough 
reassessment of previous phylogenetic datasets and direct examination of 
specimens representing 85 % of the OTUs. Scorings also drew on recently 
published and unpublished results of taxonomic reviews of the European 
Jurassic theropod record. Analysis of the new dataset recovers a 
monophyletic Tetanurae. Spinosauroidea is the most basal tetanuran clade and 
forms the sister taxon of Neotetanurae, comprising Allosauroidea and 
Coelurosauria. Spinosauroidea was previously conceived as including 
Spinosauridae and its sister taxon, Megalosauridae (or Torvosauridae). The 
present analysis finds *Afrovenator*, *Torvosaurus*, and the European Middle 
Jurassic theropods *Dubreuillosaurus*, *Eustreptospondylus*, *Magnosaurus*, 
*Megalosaurus*, *'Megalosaurus' hesperis*, and *Piveteausaurus* as 
megalosaurids. Previously unrecognised spinosauroid clades are recovered as 
successive outgroups to Megalosauridae + Spinosauridae: *Chuandongocoelurus* 
+ *Monolophosaurus* (Middle Jurassic, China), and; [sic] *Xuanhanosaurus* 
(Middle Jurassic, China) + (*Marshosaurus* (Late Jurassic, North America) + 
(*Condorraptor* + *Piatnitzkysaurus*; Middle Jurassic, Argentina)). This 
result demonstrates the monophyly of most European Middle Jurassic 
'megalosaurs', although *Poekilopleuron* is an allosauroid. Megalosaurids 
are not known from outside Europe during the Middle Jurassic, although 
global sampling is poor and some Chinese taxa of undetermined affinities 
[*Gasosaurus*, *Kaijiangosaurus*...] were not included in the new analysis 
due to brief published descriptions. Middle Jurassic spinosauroids dominated 
the role of apex predator in taxonomic and numerical abundance and show 
limited endemism across Pangaea. Most spinosauroid lineages went extinct at 
the end of the Middle Jurassic and were ecologically replaced by 
allosauroids."

I talked with Roger about Mickey Mortimer's hypothesis that 
*Chuandongocoelurus* is the sister-group of *Elaphrosaurus* (presented here 
a few years ago). He has seen the specimen, as well as *Monolophosaurus*, 
and rules that out. On the other hand, he doesn't quite trust 
*Xuanhanosaurus*.

*Poekilopleuron* as an allosauroid is a surprising result!

The oldest known tetanuran is then *Magnosaurus nethercombensis* from the 
Bajocian (2nd of the 4 stages of the Middle Jurassic). I wonder if it's the 
only known Bajocian dinosaur in general...