RE: Context for *Duriavenator*: Benson's tetanuran phylogeny

[Michael Mortimer <mickey_mortimer111@msn.com>]

David Marjanovic wrote-

> 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 published and unpublished results of taxonomic reviews of the European 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*.

I no longer trust my idea it was an elaphrosaur because a photo of the specimen 
shows the presacral vertebrae are far too large to go with the rest of the 
elements.  I wonder which part Benson used.  None of it seems very similar to 
Monolophosaurus or spinosauroids, but maybe the description is misleading.
 
>From my own studies, finding the 'basal tetanurines' (Piatnitzkysaurus, 
>Condorraptor, Xuanhanosaurus) as spinosauroids is quite possible, but so is 
>finding them in their more standard position or as the avetheropod sister 
>group.  Similarly, Monolophosaurus as a basal spinosauroid seems possible.  I 
>do wonder what material Benson included as Megalosaurus, and why.
 
Mickey Mortimer
The Theropod Database- http://home.comcast.net/~eoraptor/Home.html