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Animal Flight Origins

May 22, 2016

With the CSVP 2016 excerpt illustrating that bird flight did in fact never went through a gliding stage, lets compile how flight evolved among animals:

Bats

Long suspected to be derived from evasive fluttering rather than gliding. Padian 2008 seems to confirm this as a mechanism of bat flight development: no studies that I can think off disputed this.“Trees down”, as early bats were arboreal and evasive fluttering basically boils down to falling from a high point flapping your arms. Of relevance are some recent studies that conclude that bat wings developed drastically quickly:

https://www.washingtonpost.com/news/speaking-of-science/wp/2016/03/28/scientists-investigate-the-weird-genetics-of-bat-wings/

Birds

“Ground up” through unclear means. Possibly related to the arm motions paravians like deinonychosaurs used when subdueing prey. Hindwings likely held a role in the development of avian flight.

Pterosaurs

The most mysterious since we have nothing in the way of transitional forms. However, the fact that Scleromochlus is a hopper and that non-pterodactyloid pterosaurs have hindlimbs well adjusted for hopping (Witton 2015) seems to heavily imply that pterosaurs evolved from terrestrial hoppers that somehow learned to use the forelimbs to launch themselves. “Ground up”.

Insects

Generally thought to be derived from fluttering like in bats. “Trees down”.

Alticonodontines

Only speculated based on the locations of Ichthyoconodon, Dyskritodon and Astroconodon, the former being particularly close to the known gliding forms Volaticotherium and Argentoconodon. Of note is that Volaticotherium‘s hand is known to be highly incomplete (only metacarpal bases), so the possibility that it was itself (and, by default, Argentoconodon) volant cannot be ruled out.“Trees down” either way, as Volaticotherium shares metatarsal and limb proportion similarities with known arboreal mammals like squirrels and primates.

Freshwater fishes

Hatchetfish and butterflyfish are suspected of using their pectoral fins to jump in ‘flight strokes”, though this has been contested in recent times.

Conclusions

– Powered flight did not evolve from gliding and gliding, as far as it is known, cannot develop into powered flight, as previously discussed.

– Both “ground up” and “trees down” methods appear to be roughly balanced, though the former may be the more common option among vertebrates should alticonodontines not be volant.

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