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

[Ronald Orenstein <ron.orenstein@rogers.com>]

This may well be true. I was struck, on the one occasion many years ago when I 
had to take wing measurements from bats on an OTS course in Costa Rica, how 
long and narrow the wings of molossids were compared to others. They seemed 
unable to take off even if we tossed them into the air on release. We had to 
release them on tree trunks, after which they climbed pretty much out of sight 
before taking off. The closest avian analogy in general wing shape that I could 
come up with was a shearwater or an albatross - which of course doesn't mean 
that molossids fly like albatrosses!  They are probably too small, among other 
things. I presume they hunt above the canopy where manouverability isn't a big 
problem, but I admit I don't know. 

Ronald Orenstein 
1825 Shady Creek Court
Mississauga, ON
Canada L5L 3W2
ronorenstein.blogspot.com

On Jan 6, 2017, at 1:15 PM, Mike Habib <biologyinmotion@gmail.com> wrote:

>> 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
>