FEET OF EARLY BIRDS

["Matthew Troutman" <m_troutman@hotmail.com>]

<<<Does someone tell me what's means that the Arctometatarsalian 
condition is reversed in Archaeopteryx, Ornithurine and Enanthiornithine 
birds?>>>

<<The arctometatarsalian condition is 'pinching' of the third metatarsal
(long bone of the foot) between the second and fourth metatarsals (Dr 
Holtz will explain this better than me). Your stating means that the 
common ancestor of *Archaeopteryx*, Ornithurae and Enanthiornithes had 
the arctometatarsalian condition, but that these taxa secondarily lost 
this feature.>>

Actually, early birds never had the arctometatarsalian condition unless 
troodontids prove to be closer to birds than dromaeosaurs, following the 
previous arguments of Currie.  Several workers (most recently Forster et 
al.) have started putting Troodontidae closer to Aves than 
Dromaeosauridae (which _Archaeopteryx_ is most similiar).  Currie 
started this based on pnematic features and mainly the possession of a 
fenestra pseudorotunda and medial rotation of the quadrate head.  (Two 
features that interestingly are present in crocodylomorphs.) However, 
dromaeosaurs (and most maniraptoriforms) these features.  

Anyway, the Chinese protobirds do not show a arctometatarsalian 
condition and neither do dromaeosaurs, so the lack of the condition is 
not evidence for a reversal.  

Matt Troutman

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