ARCTOMETATARSALY

[Tetanurae <Tetanurae@aol.com>]

Jaime Headden wrote:
<<1) The first type is dorsal fusion, with mtIII adducted between II
   and IV (it is not actually "pinched") so this is not a true
   arctomet foot. An elmisaurid foot, basically.>>

Certainly.  Elmisauridae was scored as having an arctometatarsus in Holtz
1994, so that's why I included it as a type of arctometatarsaly.  Elmisaurids
or caenignathids or whatever they're called...  are closer to oviraptorids.

<<2) The arctomet foot, with mtIII "pinched" between mt's II and IV, not 
   reaching to proximal surface as in [1]. This is seen in
   tyrannosaurs and bullatosaurs, suggesting closer relationship than
   any other groups (tyrannos and ornithos and troodonts, excluding
   everything else).>>

Additionally, MT III is somewhat sigmoid at its distal end.  The proximal end
of MT III is reduced at the tarsus.

<<3) The enantiornithine foot, with mt's II-IV fused along full length
   without pinching or adduction of mtIII.>>

How is this an arctometatarsus?  Maybe Tom can clarify this, but doesn't an
arctometatarsus require MT III to be pinched?

<<4) Apparently, the alvarezsaurid foot may be a variation on types 1 or 
   3, or its own type, with mtIII adducted _and_ fused proximally and
   distally, mtIII appearing only in posterior and distal aspects,
   totally occluded from proximal and dorsal except at the plantar
   end.>>

MT III is not just adducted, but it is reduced proximally, like a true
arctomet pes.  I believe it is so reduced in _Parvicursor_ that it does not
even reach the tarsus proximally.  

Peter Buchholz
Tetanurae@aol.com