Zoology isn't my cup of tea, physics is, so I can't provide an example, but the rendering I saw made it look like it had a tail more built along mammalian lines, presumably for the usual rudder purpose on the ground, I could see the tail taking over the normal rudder job for birds as a superior method and any foot rudders phasing out as obsolete, though one would expect to see some sort of leftover as evidence, a nub or something.

Nope, couldn't say, this is far from my area of expertise, other than my judgement as a physicist that it represents a reasonable actual flight method, doesn't mean it's real of course, a Boeing 747 is a pretty good flight design too, I'm not expecting to see any of those in the fossil record... maybe a DC-8 if the scientoligists are to be believed though.