Re: [dinosaur] 2016 in paleontology + Dippy's last days in London + burrows around Omeisaurus + more

[Mike Habib <biologyinmotion@gmail.com>]

> On Jan 5, 2017, at 4:44 PM, Ronald Orenstein <ron.orenstein@rogers.com> wrote:
> 
> This is a point that bothers me as well. The only examples I can think of 
> (based on personal observation) of a powered flyer that needs to gain 
> considerable altitude in order to launch into the air (presumably by gliding) 
> are molossid bats.

Bats typically launch from perches via “slingshot” mechanisms (i.e. they start 
to flap and complete 3-4 full cycles before letting go), so there isn’t really 
a gliding phase. Molossids seem to be incapable of ground leaping (in contrast 
to most other bats), which is likely why they have to climb before takeoff. So 
even then, there doesn’t seem to be a real link to gliding.


—Mike


Michael Habib, MS, PhD
Assistant Professor, Cell and Neurobiology
Keck School of Medicine of USC
University of Southern California
Bishop Research Building; Room 403
1333 San Pablo Street, Los Angeles 90089-9112

Research Associate, Dinosaur Institute
Natural History Museum of Los Angeles County
900 Exposition Blvd, Los Angeles, CA 90007

biologyinmotion@gmail.com
(443) 280-0181






> On Jan 5, 2017, at 4:44 PM, Ronald Orenstein <ron.orenstein@rogers.com> wrote:
> 
> This is a point that bothers me as well. The only examples I can think of 
> (based on personal observation) of a powered flyer that needs to gain 
> considerable altitude in order to launch into the air (presumably by gliding) 
> are molossid bats. I can't think of a bird in that category,although some 
> poor flyers (eg Kokako) do what seem to be wing-assisted leaps from upper 
> branches to get airborne, and some water birds such as shearwaters need a 
> running start on water. Is it possible that gliding in a non-flyer is not a 
> good precursor for flapping flight, and that true gliders (eg colugos) are 
> not "evolving towards" flight but are on a different, perhaps incompatible 
> evolutionary path (so that powered flyers start out as leaders/flappers from 
> an early stage)?
> 
> Ronald Orenstein 
> 1825 Shady Creek Court
> Mississauga, ON
> Canada L5L 3W2
> ronorenstein.blogspot.com
> 
>> On Jan 6, 2017, at 8:04 AM, Mike Habib <biologyinmotion@gmail.com> wrote:
>> 
>> 
>>> David Černý <david.cerny1@gmail.com> wrote:
>>> 
>>>> (Mayr 2016) accepts and reiterates
>>>> Senter's (2006) conclusion that flapping flight was biomechanically
>>>> impossible for early birds, mentions "[t]he physical and biological
>>>> implausibility of a strict 'ground-up' origin of flight" (p. 39), and
>>>> presents a stationary leaping take-off as a highly derived locomotory mode
>>>> associated with a complex of pectoral girdle and wing adaptations that is
>>>> unique to a couple of deeply nested neornithine lineages.
>> 
>> The Mayr (2016) argument here perplexes me a bit; I may be missing 
>> something. In living birds, running takeoff is a mostly a derived feature of 
>> water birds, and I cannot find a parsimonious way to map it onto any recent 
>> phylogeny that avoids multiple derivations. In other words, running takeoff 
>> seems to be derived, at least within the crown group. 
>> 
>> I'm also not clear (I'll have to go read the work in detail) why Mayr has 
>> such a focus on wing characters for stationary leaping launch, since launch 
>> mode is mostly dependent on hind limb morphology and substrate. Wing 
>> characters influence climb out, but not running vs leaping launch mode 
>> preference.
>> 
>> 
>>> Mayr (2016) is highly skeptical of any scenario for the origin of
>>> flight that that doesn't involve a "gravity-assisted" gliding stage.
>> 
>> The weird thing here, for me, is that living arboreal flyers still use 
>> leaping launch modes to initiate flight - even the unpowered ones. There are 
>> no living gravity launchers (that we have found so far, anyway). So even if 
>> Mayr had good evidence for arboreal behavior near the origin of avian 
>> flight, I'm not sure how that would yield a "gravity assisted" model. I 
>> suppose he's referring to the gliding phase itself? 
>> 
>> Cheers,
>> 
>> --Mike
>