Re: [dinosaur] Bat flight evolution + dolphin skull shape (free pdfs)

[Tim Williams <tijawi@gmail.com>]

Mickey Mortimer <mickey_mortimer111@msn.com> wrote:

> As for integument, recall that Unwin (2000) found Sharovipteryx is 
> characterized by "the presence of long, thin, closely-packed fibres within 
> the membranes that exhibit a striking degree of similarity to the
> wing-fibres (aktinofibrillae) of pterosaurs", which seems about as unusual to 
> converge as feathers of the pterosaur/Tianyulong level are.

In part, I guess it depends on whether or not you accept that _Ozimek_
represents a link between _Sharovipteryx_ and (other) protorosaurians.

Returning to the original paper by Anderson and Ruxton... I don't know
enough about bats (extant or fossil) to assess the plausibility of
their hypothesis: that powered flight evolved three separate times in
Chiroptera (each time from an arboreal, nocturnal mammal with long,
webbed digits).  Although the authors draw on _Yi_ and _Amboperyx_ as
inspiration, they overlooked a huge swathe of theropod literature in
stating that "these members of the arboreal dinosaur family
Scansoriopterygidae are unique in being the only non-avian dinosaurs
potentially capable of flight".  As numerous papers have made clear
(including brilliant work in the recent AMNH Bulletin monograph on
pennaraptoran theropods), there is solid evidence that powered flight
evolved at least three times in pennaraptorans: microraptorines
(_Microraptor_), unenlagiines (_Rahonavis), and avialans (beginning
with _Archaeopteryx).  So having a precedent of multiple origins of
theropod flight could have bolstered Anderson and Ruxton's hypothesis
of multiple origins of chiropteran flight.

Tyler Greenfield <tgreenfield999@gmail.com>

> Anderson stated on Twitter that she wasn't aware of the problems with Peters' 
> work when she wrote the paper. This is understandable as she's not an 
> archosaur researcher.

Yes, and the paper in question (Peters, 2001) was published in a
respectable journal (Historical Biology), not from his rubbish
pterosaur blog.

Also, for another group of winged animals, I'd query Anderson and
Ruxton's statement that the 400 m.y.o. _Rhyniognatha_ is the "first
known winged insect".  Little _Rhyniognatha_ is known only from
mouthparts.  These have been thought to have come from a flying insect
because of their similarity to mouthparts from known winged
(pterygote) insects.  So we don't have direct evidence of
_Rhyniognatha_being winged.  Also, there is an opposing view that
_Rhyniognatha_ is a myriapod, not an insect.