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Re: Metatarsal fusion/nonfusion: birds/theropods



In a message dated 97-03-15 22:42:27 EST, dtanke@dns.magtech.ab.ca (Darren
Tanke) writes:

<< 2. All fossil birds have fused metatarsals, possibly except ARCHAEOPTERYX
 (although apparently the Maxberg specimen shows co-ossification). >>

_Mononykus_, presently considered by some to be a bird above _Archaeopteryx_
in the avian cladogram, does not have fused metatarsals. It's foot is rather
typically arctometatarsalian. By itself, this does not rule out classifying
_Mononykus_ at this level, because metatarsal fusion could be a character
that appeared above >both< _Archaeopteryx_ and _Mononykus_ in the cladogram,
and the arctometatarsalian foot could have developed independently for
_Mononykus_. But the foot anatomy of _Mononykus_ >also< is not inconsistent
with placement of _Mononykus_ with other arctometarsalian theropods, lower
down in the avian cladogram.