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RE: Origin of flight in birds and bats

As an addendum to the second, 


  Jaime A. Headden
  The Bite Stuff (site v2)

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 

> Date: Sat, 12 Nov 2011 15:16:12 -0500
> From: bh480@scn.org
> To: dinosaur@usc.edu
> Subject: Origin of flight in birds and bats
> From: Ben Creisler
> bh480@scn.org
> A couple of recent items that apparently have not been mentioned on the
> DML:
> Flapping robot gives insights into flight
> http://www.sciencedaily.com/releases/2011/10/111017214919.htm
> K. Peterson, P. Birkmeyer, R. Dudley and R. S. Fearing (2011)
> A wing-assisted running robot and implications for avian flight evolution.
> Bioinspiration & Biomimetics 6(4):
> doi:10.1088/1748-3182/6/4/046008
> http://iopscience.iop.org/1748-3190/6/4/046008/
> Abstract
> DASH+Wings is a small hexapedal winged robot that uses flapping wings to
> increase its locomotion capabilities. To examine the effects of flapping
> wings, multiple experimental controls for the same locomotor platform are
> provided by wing removal, by the use of inertially similar lateral spars,
> and by passive rather than actively flapping wings. We used accelerometers
> and high-speed cameras to measure the performance of this hybrid robot in
> both horizontal running and while ascending inclines. To examine
> consequences of wing flapping for aerial performance, we measured lift and
> drag forces on the robot at constant airspeeds and body orientations in a
> wind tunnel; we also determined equilibrium glide performance in free
> flight. The addition of flapping wings increased the maximum horizontal
> running speed from 0.68 to 1.29 m s−1, and also increased the maximum
> incline angle of ascent from 5.6° to 16.9°. Free flight measurements show a
> decrease of 10.3° in equilibrium glide slope between the flapping and
> gliding robot. In air, flapping improved the mean lift:drag ratio of the
> robot compared to gliding at all measured body orientations and airspeeds.
> Low-amplitude wing flapping thus provides advantages in both cursorial and
> aerial locomotion. We note that current support for the diverse theories of
> avian flight origins derive from limited fossil evidence, the adult
> behavior of extant flying birds, and developmental stages of already volant
> taxa. By contrast, addition of wings to a cursorial robot allows direct
> evaluation of the consequences of wing flapping for locomotor performance
> in both running and flying.
> ===
> Origin of flight in bats
> http://www.nature.com/news/ancient-bats-got-in-a-flap-over-food-1.9304
> SVP Abstracts 2011
> PADIAN, Kevin, University of California, Berkeley, CA, USA; DIAL, Kenneth,
> University of Montana, Missoula, MT, USA
> Living bats differ from other flying vertebrates (birds and pterosaurs) in
> having poor sight, echolocating, stressing slow, maneuverable fight, and
> seldom gliding. It has generally been assumed that gliding is a necessary
> precursor to fight, but phylogenetic analyses show that no gliding forms
> are found among the closest relatives of flying forms, and many gliding
> lineages have evolved with no apparent tendencies to powered fight. The
> most basal known bats could fly, but the most basal Onychonycteris lacked
> bony specializations for echolocation, which has suggested that flight
> evolved frst. However, other mammals such as the tenrec do not fly but can
> echolocate in a more rudimentary way, and they lack chiropteran bony
> specializations for this. Nocturnal animals generally evolve enhanced
> vision, but animals that live in almost total darkness (e.g., caves) tend
> to reduce sight. Cave insects also tend to lose flight capacity. The visual
> capabilities of the earliest bats are ambiguous, but nearly all living bats
> are crepuscular, roosting in dark places.
> We mapped traits related to echolocation, locomotion, vision, diet, and
> habitat in crown and stem bats. Results suggest that echolocation may be an
> “evolvable,” modular trait that has been hard-wired to various degrees in
> mammals. Basal bats are inferred to have been insectivorous, but they may
> have hunted differently than living bats do. Phylogenetic mapping shows
> that neither the ability to fly well nor to echolocate well may have been
> basal to bats; living in caves and feeding on poorly mobile insects may
> have been basal habits at least for crown-group bats. No outgroups to bats
> are or apparently were bipedal; thus the forelimbs of bats could only be
> freed to evolve powered fight if they were no longer necessary to standard
> quadrupedal locomotion. All bats can climb quadrupedally and this seems
> basal for crown-group bats. Caves have fewer predators than trees, and the
> ability to suspend the body from the roofs of caves appears to have been
> possible for all known Chiroptera, living and extinct. The features of cave
> habitats, although poorly fossilized, may explain much about the origin of
> bats.
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