Episode 148 – Gliding – COMMON DESCENT

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Powered flight has only evolved a few times, but it’s incredible how many times and how ways evolution has produced organisms that sail through the sky. This episode, we discuss the astonishing diversity – past and present – of Gliding.

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Almost Like Flying

Only a few lineages of life have ever evolved powered flight, the ability to move through the air in any direction without the help of the wind. But many organisms have evolved the ability to glide, using specially-adapted body parts to catch the air, allowing them to fall slowly and sometimes to cover great distances in the process.

Gliding is extremely useful for getting away from non-airborne threats, for quickly navigating an environment, or simply for avoiding a fall from a great height. And gliding is much easier than flying, requiring far less energy and fewer extreme adaptations of the body. So while the only true fliers on Earth are insects, pterosaurs, birds, and bats (and machines), it’s no surprise that gliding has evolved many times in many ways.

So Many Gliders

Animals aren’t the only gliders! Plenty of plants have seeds with specialized structures to catch the air and let the wind carry them across the landscape.
**Top left**: Winged catalpa seeds. JonRichfield, CC BY-SA 4.0
**Top right**: Winged maple seeds. Photoholic1, CC BY-NC-ND 2.0
**Bottom left**: Eocene fossil fir seeds. Kevmin, CC BY-SA 4.0
**Bottom right**: Eocene fossil pine seeds. Kevmin, CC BY-SA 3.0

There are many species of flying fish who use their strong tails to push out of the water and their broad fins to glide over the waves to avoid predators.
**Top left**: Theron Trowbridge, CC BY-NC 2.0. **Top right**: Public Domain
There are also fossil flying fishes, including ancient members of modern groups as well as an entirely extinct Triassic group called Thoracopteridae.
**Bottom left**: *Thoracopterus*, Triassic. Ghedoghedo, CC BY-SA 3.0
**Bottom right**: *Thoracopterus*, Triassic. Ghedoghedo, CC BY-SA 4.0
Read more about the Triassic flying fish.

There are many gliding mammals, including rodents, marsupials, and colugos, and they all glide by expanding flaps of skin that connect to their limbs.
There are also extinct groups of furry gliders, including the Jurassic mammal *Volaticotherium* and the Jurassic mammaliaforms, the haramiyidans.
**Top left**: Sugar glider, Matteo De Stefano/MUSE, CC BY-SA 3.0
**Top right**: Flying squirrel, Pavel Kirillov, CC BY-SA 2.0
**Bottom left**: *Volaticotherium* fossil, Jonathan Chen, CC BY-SA 4.0
**Bottom right**: *Volaticotherium*, Nobu Tamura, CC BY-SA 3.0
See: Rare Fossils Reveal New Species of Ancient Gliding Mammals

Gliding snakes spread their ribs and undulate through the air like weird squiggly frisbees. Image from Holden et al. 2014
See: How Snakes Fly

*Draco* lizards have extra-long ribs that support extendable wings.
**Left**: *Draco spilonotus*, A.S. Kono, CC BY-SA 3.0
**Right**: *Draco taeniopterus*, Psumuseum, CC BY-SA 3.0
See: How *Draco* lizards fly

The Cretaceous lizard *Xianglong* had extended ribs just like modern *Draco* lizards, despite belonging to a different branch of the lizard family tree.
Images from Li et al. 2007
See: Ancient lizard glided on stretched skin

During the Triassic Period, the Kuehneosaurids included several species of gliding reptiles who also had extra-long ribs. It’s a common strategy!
Image from Stein et al 2008

Another Triassic glider: the bizarre *Sharovipteryx*, which glided using a wing-like membrane stretched between the back legs.
**Left**: *Sharovipteryx* fossil. Kumiko, CC BY-SA 2.0
**Right**: One possible gliding strategy for *Sharovipteryx*. More research (and more fossils) will be needed to determine if they could actually glide like this. Image by Dmitry Bogdanov, CC BY-SA 3.0
See: *Sharovipteryx*, the Triassic reptile with leg-wings
And: Flight of *Sharovipteryx mirabilis*: the world’s first delta-winged glider

The oldest known gliders are the Weigeltisaurids, early reptiles from the Permian. These had a series of extra rod-like bones that extended from the sides of their bodies (not ribs!) to support their wings.
Image from Pritchard et al. 2021

There are also some non-bird dinosaurs that are thought to have been gliders!
*Microraptor* had glide-capable wings on its front and back limbs, and Yi seems to have had a pair of bat-like membranous wings.
**Top left**: *Microraptor* fossil, Hone et al 2010;
**Bottom left**: *Microraptor* art, Durbed, CC BY-SA 3.0
**Top right**: Yi fossil, Kumiko, CC BY-SA 2.0
**Bottom right**: Yi art, Nobu Tamura, CC BY-SA 4.0
Read more about *Microraptor* and Yi.

That’s not even all of the gliders! There are also gliding frogs, gliding ants, gliding spiders, and more!

To study gliders of the past, researchers will often assess the aerodynamic capabilities of their bodies. Sometimes, this involves creating digital or physical models to test out in a wind tunnel!
**Left**: *Microraptor* gliding models from Evangelista et al 2014
**Right**: *Keuhneosuchus* gliding model from Stein et al 2008

Video Footage:
Flying fish
Gliding frogs
Flying squirrels
Colugos
Sugar gliders
Draco lizards
Flying snakes

Learn More

Flying and Gliding animals

Changes in the tree canopy facilitated the evolution of the first-ever gliding reptile, new study suggests

Evolution of gliding in Southeast Asian geckos and other vertebrates is temporally congruent with dipterocarp forest development (technical, open access)

Gliding and the Functional Origins of Flight: Biomechanical Novelty or Necessity? (technical, open access)

The Biology of Gliding in Flying Lizards (Genus Draco) and their Fossil and Extant Analogs (technical, open access)

Biplane wing planform and flight performance of the feathered dinosaur Microraptor gui (technical, open access)

Potential for Powered Flight Neared by Most Close Avialan Relatives, but Few Crossed Its Thresholds (technical, open access)

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Mark E Zawadzki September 18, 2022 / 8:21 pm

Cats “parachute ” too. This sort of behavior can occur in larger vertebrates ( > squirrel)
https://drmartypets.com/falling-cat-physics/

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E M Culver November 6, 2022 / 7:36 pm

Humans, when they skydive, can control their rate of fall to some extent by changing their posture. This can be useful, in that there was a case where a skydiver’s parachute streamed (came of of the pack but didn’t expand into that nice, large canopy) and he was able to survive by going into the highest drag position. He did require a bit of surgery, as he was reported to have broken every bone in his face, several ribs, and a few long bones.

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