Episode 151 – Tails

Listen to Episode 151 on PodBean, YouTube, Spotify, or wherever you listen to your favorite podcasts!

For most animals, the body doesn’t end at the hips! That final stretch of anatomy comes in many shapes and sizes suitable to a wide variety of lifestyles. This episode, we discuss the diversity and biological importance – past and present – of Tails.

In the news
Clustered Lystrosaurus fossils seem to indicate repeated droughts
Incredible fossil site preserves the earliest known fish jaws
That same fish site also provides clues to early evolution of paired fins
A detailed look at paleontology representation in video games (read the study here)

Right Behind You

In vertebrate animals, the tail is the part of the spinal column (plus surrounding tissues, of course) that extends past the rear end of the animal. But, of course, it’s more complicated than that. There are lots of structures among invertebrates that we call “tails” and which serve similar purposes: in many arthropods, such as certain insects, the final body section, the metastoma, extends into a tail-like structure, and many crustaceans have a long telson which forms their version of a tail, just to name a couple. And all these many types of tails come in a huge array of forms and functions.

The shape and length of an animal’s tail is commonly tied to its lifestyle. One of the most common uses for a tail is locomotion. Many climbing animals use their tails for extra support to move through tree branches, and plenty of swimming animals use their tails as their primary means of propulsion through the water.
Left: Chameleon, Charles J. Sharp, CC BY-SA 4.0
Right: Whale tail, Liza, CC BY 2.0
Surely you can think of dozens of other ways tails have been modified for various functions, but here are a few examples.
Top left: Display: Peacocks have relatively short tails covered in very long feathers, which they use for colorful displays. Image by Peter Andersen, CC BY-SA 3.0
Top right: Out of the way: In some animals, like bobcats, a short tail (or for some, no tail at all), is best. Image by Kenneth Cole Schneider, CC BY-NC-ND 2.0
Bottom left: Defense: Rattlesnakes famously use their tails as a noisy deterrent to ward off threats. Image by Nathan Rupert, CC BY-NC-ND 2.0
Bottom right: Offense: Scorpions use their “tails” as a weapon, primarily used for hunting prey. Image by MostlyDross, CC BY 2.0
Evolutionarily, tails have arisen many times and have been lost many times. But a bunch of species have also evolved the ability to lose tails during life. This is called autotomy.
Left: A lost lizard tail, like this skink’s tail, is a colorful distraction to keep a predator’s attention while the rest of the animal (with all the important bits) gets away. Image by Metatron, CC BY-SA 3.0
Right: Many animals that autotomize their tails can also grow them back! Image by Anita Gould, CC BY-NC 2.0

Tails as Old as Time

As we can see, the shape of an animal’s tail is tightly linked to its lifestyle, whether the tail is being used for locomotion, display, defense, or some other purpose. So it’s no surprise that paleontologists are often excited when they can get a good look at a fossil animal’s tail, as they can lead to great insights into the lives of extinct species.

Some tails from the past.
Top left: Many suggestions have been made about the functions of the tails of eurypterids, also known as sea scorpions. Image by James St. John, CC BY 2.0
Top right: Tons of research has focused on dinosaur tails. Sinosauropteryx likely used its colorful tail for display, as well as other potential uses like keeping its balance. Image by Sam / Olai Ose / Skjaervoy, CC BY-SA 2.0
Bottom: Glyptodonts are among the very few animals in history that have had tail clubs (see also ankylosaurs). Image by Robert Bruce Horsfall, public domain

Sometimes, fossil tails are key to understanding ancient species’ habits and evolution. Among dinosaurs, for example, tail shape is a key feature that signals the transition toward modern birds, and the recent discovery of a tall, flat Spinosaurus tail has added support to suspicions that these dinosaurs spent lots of time in water. There are even fossil examples of tail loss and regeneration!

Learn More

A Tale of the Tail (2021), an overview of tails, tail evolution, and what’s going on with humans

Fish fossils reveal how tails evolved (2016)

Simulations show how dinosaurs used their tails while walking (2021)

Convergent evolution in the tail weapons of mammals and dinosaurs (2019)

From dinosaurs to birds: a tail of evolution (2014, technical, open access)

If you enjoyed this topic and want more like it, check out these related episodes:

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