Re: ARCTOMETATARSALY

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

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


 It isn't. The enantiornithine foot is very different from that of the 
typical arctometatarsalian foot in that metatarsal III is not 
constricted. The enantiornithine tarsometatarsus is proximally fused, 
though not to the tarsal cap , in contrast to that of ornithurines, 
where it is fused distally-to-proximally and the tarsal cap is fused to 
the metatarsus. The enantiornithine arrangement is seen in 
Arhcaeopteryx, where the metatarsals are fused proximally. This 
arrangement does not seem to be seen in "Rahona", where the metatarsals 
are unfused. What effect this has on character polarity in Aves is 
problematic, because it can easily be a convergence or a synapomorphy 
with the Enantiornithes and Confuciusornis. 

MattTroutman

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