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Saltopus... a silesaurid?



>From Benton and Walker (2011):


     "_Saltopus_ is placed unequivocally within Avemetatarsalia,
      Dinosauromorpha and Dinosauriformes, and it sits between
     _Pseudolagosuchus_ and the unnamed clade that combines
     Silesauridae and Dinosauria (Nesbitt et al. 2010), but with
     only 45% bootstrap support."


Here, the Silesauridae includes _Lewisuchus_, _Silesaurus_,
_Sacisaurus_, and _Eucoelophysis_.  So _Pseudolagosuchus_ and
_Lewisuchus_ are split up, with _Saltopus_ sitting in between.


The thing is, several previous studies have speculated that
_Lewisuchus_ and _Pseudolagosuchus_ are actually the same taxon - with
Nesbitt et al. (2011; the _Asilisaurus_ paper - Supp Info) describing
this issue in detail.  Although Nesbitt et al. "strongly suspect that
_Lewisuchus_ and _Pseudolagosuchus_ are the same taxon", they
refrained from formally synonymizing the two.


When Nesbitt et al. placed _Lewisuchus_ and _Pseudolagosuchus_ in a
phylogeny as separate taxa, all the most parsimonious trees recovered
both taxa at the base of Silesauridae.  However, individual trees
differed in which of the two taxa (_Lewisuchus_ and
_Pseudolagosuchus_) is actually the *most* basal within the
Silesauridae.  Nesbitt et al. go on to say:


      "This is probably a result of the fact that the taxa do not
       preserve informative overlapping regions of the skeleton;
       the silesaurid synapomorphies in _Lewisuchus_ are
       preserved in the cranium and anterior axial skeleton,
       whereas the silesaurid synapomorphies for
      _Pseudolagosuchus_ are preserved in the femur."


This made me wonder.   *If* _Lewisuchus_ and _Pseudolagosuchus_ were
combined into a single taxon (OTU), and the phylogenetic analysis of
Benton and Walker (2011) was re-run with _Saltopus_ included... would
_Saltopus_ fall out as a member of the Silesauridae?  Is this
something someone (Mickey?) could test?


Another interesting thing in the Benton and Walker paper is that the
tree (which is based on characters in Brusatte et al., 2010) finds
decent support (61%) for a _Scleromochlus_ + Pterosauria clade
(=Pterosauromorpha - although not given here).


Finally, one peculiar aspect of the paper is the usage of ranks in the
systematic treatment of _Saltopus_: Infradivision Dinosauromorpha,
Subinfradivision Dinosauriformes, etc.  I can't see the point of these
quasi-Linnaean ranks at all.





Cheers

Tim