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Re: Moasaurus

Mike Eagle wrote-

> Was it really a "bird", or was it a true dinosaur (perhaps many times
> derived?), continuing to eek out an existance in a refugium that was once
> part of Gondwana, now known as New Zealand (and by the cinema as "The Lost
> World")? It looks like a dinosaur to me and I'm sure that cladistics would
> prove this right in the present light of dinosaurian morphology. The fused
> metatarsus in birds vs. dinosaurs may be a stumbling block to the dinosaur
> suggestion! What do some of the more knowledgeable vertebrate specialists
> think?

Although I lack good pictures of a moa skeleton, even a passing glance at
some available figures shows many characters synapomorphic for advanced
birds and not seen in many dinosaurs.  The femur is very short compared to
the tibiotarsus; there is a large patellar groove on the distal femur; the
tibiotarsus is completely fused; the fibula is reduced so it does not
contact the tarsus; the metatarsus is completely fused; the ischium is
subequal in length to the pubis; the pubis lacks a distal foot.  I'm sure a
more knowledgable ornithologist would know of many other such characters,
perhaps including a large sacral vertebral count and the lack of a dorsal
jugal process.  Any supposedly plesiomorphic characters, such as the lack of
a pygostyle and furcula are no doubt due to flightlessness and are
secondarily lost.  Added to the large amount of morphological data are the
molecular data.  Recently, the complete mitochondrial genome of two moa
species was sequenced and compared to other ratites (Cooper et al. 2001).
The most parsimonious tree shows rheas less derived than moas within
ratites.  Keep in mind that tinamous and neognaths are successive sister
groups to ratites in molecular phylogenies as well.  So I'm afraid it isn't
likely at all that moas are living non-avian dinosaurs.

Cooper A, Lalueza-fox C, Anderson S, Rambaut A, Austin J, Ward R,
Complete mitochondrial genome sequences of two extinct moas clarify
ratite evolution, Nature 2001; 409: 704-7

Mickey Mortimer