Episode 163 – Claws

Listen to Episode 163 on PodBean, YouTube, Spotify, or wherever you listen to your favorite podcasts!

Check the fingers and toes of your favorite vertebrates and you’re likely to find hardened little end-caps on them! This episode, we discuss the many forms and functions of Claws.

In the news
This ancient amphibian swam around like a croc
Linking major moments in the evolution of ants and angiosperms
Fossil eggshells reveal egg-laying habits of Troodon
These giant snails appear to have been cooked by ancient humans

The Claw!

The term “claw” is used to describe a wide variety of body parts, usually pointy bits at the ends of limbs or digits. In technical terms, “true claws” – also called ungues – are specifically found in tetrapods; they consist of the last bony element of a digit and the hardened sheath that covers it. These come in many forms, including sharp, pointy claws; flattened fingernails and toenails; and even hooves.

This doesn’t include other claw-like structures, such as the “claws” on the feet of insects or the pincers of crabs and scorpions, although these are often used very similarly to the claws of tetrapod animals.

Top left: The claws of a crocodile foot. Image by Mara 1, CC BY 2.0
Top right: The nails of a macaque. Image by Alexas_Fotos
Bottom: The talons of a red-tailed hawk. Image by Margie Savage, CC BY-ND 2.0

Animals use claws for many purposes: climbing, digging, grabbing prey, keeping traction while running, and plenty more. Claw form and function are tightly tied, so the shape of a claw is usually a very good indicator of how the claw is used, even in cases where the differences are slight; in birds of prey, for example, subtle variations in talon shape are correlated with the varying ways that different species use their talons to handle prey.

Claws Through Time

Claw-like structures have evolved many times in vertebrates, invertebrates, and even plants. True claws seem to have first evolved around the origins of amniotes. Claws are rare in amphibians, but extremely common in reptiles, birds, and mammals, which suggests that early tetrapod claws might have been a key feature among the first amniotes as they explored habitats farther from the water’s edge.

Claws are abundant in the fossil record, including some truly famous examples like the giant claws of ground sloths or the sickle-shaped “killing claws” of dromaeosaurs. The hardened sheath of a claw – usually made of keratin – rarely fossilizes, but the underlying bone does, and the close relationship between claw form and function allows us to make reasoned interpretations about how ancient animals were using their claws.

Dinosaur claws!
Top: The hand claws of Therizinosaurus. Image by Ghedoghedo, CC BY-SA 3.0
Bottom left: The foot claws of Deinonychus. Image by James St. John, CC BY 2.0
Bottom right: The foot claws of Camarasaurus. Image by James St. John, CC BY 2.0
Various hypotheses have been proposed for the functions of the sickle-claws of dromaeosaurs.
Recent research favors the interpretation shown in F, where the animals would use these claws to immobilize prey while they eat them, similar to how modern birds of prey often use their talons.
Image by Peter J. Bishop, CC BY 4.0

Learn More

Some recent claw-related studies:
Comparing modern seriemas with sickle-clawed dinosaurs. Popular article; technical paper.
Analysis of the strange claws of therizinosaurs and alvarezsaurs. Popular article; technical paper.
Oldest fossil grooming claws in primates. Press release; technical paper.

Using claw curvature to identify lifestyle in lizards, birds, and ancient dinosaurs (technical, open access)

Development and evolution of reptile claws (technical, paywall)
Development and evolution of mammal claws (technical, paywall)


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

We also invite you to follow us on Twitter, Facebook, or Instagram, buy merch at our Zazzle store, join our Discord server, or consider supporting us with a one-time PayPal donation or on Patreon to get bonus recordings and other goodies!

Please feel free to contact us with comments, questions, or topic suggestions, and to rate and review us on iTunes

One thought on “Episode 163 – Claws

  1. llewelly April 19, 2023 / 2:44 pm

    ok, since you mentioned the cat’s claw plant, now you need to do an episode on vines and their climbing adaptations, since about half of the many plants called “cat’s claw” seem to be vines … at least as far as my very limited knowledge of plants goes. : )

    Liked by 1 person

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s