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Re: Pro(to)avis

Phil Bigelow

The less important diagnostic characters (those that are *not* avian
apomorphies) would be the ones to examine, and those possibilities are
numerous.  Maybe a mixture of Velociraptorine and Archie features?  Maybe
a mix of troodontid and Archie features?

Depending on whether you are a ground-up believer or a tree-down
believer, the creature would have been either a good runner
(cursorial-style legs) or a good climber (well-developed manus claws and
shorter legs).

Er... why? The taxa around the base of Avialae seem to be okay runners and okay climbers (Archaeopteryx, Rahonavis, Microraptor, Jinfengopteryx, Mei).

Other possibilities are:
Serrated teeth

Unlikely since Epidendrosaurus, basal troodontids (Mei, Jinfengopteryx, Sinovenator, Byronosaurus), oviraptorosaurs (Incisivosaurs, Protarchaeopteryx, Caudipteryx), alvarezsaurids and ornithomimosaurs lack serrations. Basal dromaeosaurs (Microraptor, Cryptovolans, Sinornithosaurus) have less serrated teeth than dromaeosaurids.

More teeth 

Very likely.

Elongated maxillae

I don't know about this. Jinfengopteryx and Mei have shorter maxillae than Archaeopteryx and Confuciusornis.

Longer, heavier tail

Maybe. Shenzhouraptor and Jixiangornis both have much longer tails, though Yandangornis and avebrevicaudans have shorter ones. NGMC 91 has a shorter tail, but other dromaeosaurs' are much longer. Mei has a shorter tail, Jinfengopteryx and Sinusonasus have longer ones, and Sinornithoides' is much longer. Scansoriopteryx's is comparable. Enigmosaurs' are shorter, except perhaps for Falcarius.

Less pneumaticization in the skull and in other bones

Not sure about this. While some bones trend towards a gain in pneumaticity (e.g. braincase elements, appendicular elements), others trend towards loss (e.g. snout and palatal elements). For instance, velociraptorines have pneumatic lacrimals, nasals and jugals, as well as a ventral ectopterygoid excavation, unlike Archaeopteryx.

At any rate, this taxon probably lived sometime in the late Triassic or
earliest Jurassic.

This I have to disagree with. We don't even have tetanurines from that early. Falcarius killed the segnosaurian identity of Eshanosaurus. I say Middle Jurassic, where we have taxa slightly less derived than Archaeopteryx (Epidendrosaurus), and basal paravians (Pedopenna).

Mickey Mortimer