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Re: *Microraptor* the biplane: published



David Marjanovic wrote:

What sort of fossil would cinch either side? If there definitively *was* a
biplane stage, what might we one day find?

At least two double-decked basal bird clades.

Well, I would say that you are conflating three hypotheses here:

(1) Those theropods (like _Microraptor_) that had wings on both the forelimbs and hindlimbs adopted a 'biplane' (double-decked) configuration for aerial locomotion.

(2) Long and asymmetrical contour feathers on the metatarsus are primitive for birds.

(3) The biplane configuration was ancestral to modern avian flight.

Chatterjee and Templin present a case for (1), based on anatomical/biomechanical and physical/aerodynamic data. The biplane hypothesis seems to be better supported than the alternative hypothesis, which holds that the hindlimbs of _Microraptor_ were held splayed when gliding, so that the fore- and hindwings were parallel.

However, based on phylogenetic evidence, there is currently there is little support for (2). If there was more support for (2), and (2) was combined with (1), you could build a case for (3).

Cheers

Tim

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