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juvenile Microraptor



>Before I write a details segment on Microraptor and include it in my
>phylogenetic analysis, I thought I'd comment on its size.  It is touted
as
>the "smallest known non-avian theropod dinosaur", but is it?  First of
all,
>the authors claim it is an adult.  This is based on the fused sacral
>vertebrae, the pubic symphysis, partial fusion of the last dorsal to the
>sacrum, fine tooth serrations, well-ossified cortical bone,
well-developed
>accessory trochantor, small skull/femur ratio and small sacrum/femur
ratio.
>However, according to Nick Longrich, an accessory trochantor is
>characteristic of subadult maniraptorans, such as the holotype of
>Microvenator. 
        Not exactly, but yes, three separate trochanters is a
subadult/juvenile character. The accessory trochanter is present in adults
of the derived Maniraptora (dromaeosaurs, oviraptors, therizinosaurs,
troodontids, etc.). It's the lesser trochanter which is absent, because in
adults it's fused onto the greater to form an articular crest which
buttresses against a big antitrochanter, like in birds. The accessory
trochanter is also found in adults of more primitive theropods. It is most
prominent in tyrannosaurids and struthiomimids, but it can also be made
out in all kinds of other theropods- allosaurs, megalosaurs, spinosaurs,
Bahariasaurus, even Ceratosaurus.
        -n