Re: [dinosaur] Fwd: Tyrrell's 1884 Albertosaurus skull + early bird liftoffs + near-dinosaurs + larval temnospondyl + more

[Tim Williams <tijawi@gmail.com>]

Brad McFeeters <archosauromorph2@hotmail.com> wrote:

> Does anyone think that Yi was not an arboreal theropod?


(1) I don't know.  (Speaking solely for myself.)

(2) Even if _Yi_ was an arboreal theropod, it has no bearing on the
origins of arboreality and/or flight in birds.  As the original
description states: "they [scansoriopterygids] appear to represent a
case of extreme morphological divergence near the origin of birds"  So
scansoriopterygids appears to be an aberrant/'oddball' group.

(3) It seems likely that _Yi_ was capable of some form of aerial
locomotion.  But without knowing the exact morphology or extent of the
patagium, it's difficult to infer what kind of aerial locomotion.  If
_Yi_ was capable of launching from the ground, it could reach tree
branches without climbing.  So it could be arboreal without being
scansorial.  If _Yi_ could pull off patagium-driven "ground-up"
launches, then there might be parallels between 'flight' in
scansoriopterygids and the evolution of pterosaur flight.  Pterosaur
ancestors likely had strong erect hindlimbs, as in _Scleromochlus_ and
dinosauromorphs (e.g., Witton DOI 10.7717/peerj.1018); and saltatorial
abilities in _Scleromochlus_ (http://
markwitton-com.blogspot.com.au/2014/08/scleromochlus-taylori-more-than-just.html)
would be consistent with a terrestrial leaping origin for pterosaur
flight.  But I'm straying OT here....