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FW: Microraptor hanqingi, new species from China.
I, for one, think that basal paravians and avialans were not highly arboreal.
But there are at least three features that suggest that something other than
running fast on the ground had become a new priority in the biology of basal
One is the very long leg wings, which Xu hypothesized were in conflict with
fast running. This is hard to test.
Two are the longer penultimate phalanges, seen also, I believe, in Xiaotingia.
Three is the evolution of the reversed hallux. It is at least slightly reversed
by Jeholornis and more so, as well as longer and stronger, by Changchengornis.
I do assume that this indicates that being good at gripping branches became
important to their survival early in the evolution of the modern flight
I guess then a testable prediction is that, if the forms in which incipient
flight evolved were not using tree habitats at all (if strict ground up is
correct), the 1st digit should begin its long sequence of adaptations AFTER the
flight apparatus is assembled.
Instead I interpret the descent of the hallux to lie close to the other toes in
Microraptor, and more so in Epidendrosaurus and Xiaotingia to possibly indicate
the first steps of selection for branch walking. After these incipient stages
there is a long and complex radiation of avialans with increasing rotation of
The small body size, large wings, showy tails, feathered legs, long penultimate
phalanges, and descending hallux of basal paravians could be seen as consistent
with animals that were using tree habitats some of the time and adapting to
those habitats. If the descending hallux and penultimate phalanges have nothing
to do with branches, and small animals can run just fine with long wings on
their legs, then this is not evidence for branch walking at all. But maybe then
the burden lies with others to explain the very long and diverse series of
morphological changes in Mt I.