What crocodile bones teach us about dinosaurs

Short Wave

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4.7 • 6.5K Ratings

🗓️ 9 March 2026

⏱️ 12 minutes

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Summary

Paleontologists have often determined how old a dinosaur was by counting the growth rings in its bones. Just like with trees, it was thought that each ring corresponded to a single year of age. But researchers who studied crocodiles at an outdoor recreation center near Cape Town appear to have poked a hole in that approach. In the crocodiles, which are some of the closest living relatives of dinosaurs, there was more than one growth ring laid down per year. The results contribute to a growing debate over the best way to age animals.

Read more of freelance science reporter Ari Daniel’s story here.

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Transcript

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0:00.0	Support for NPR and the following message come from the William and Flora Hewlett Foundation,
0:05.4	investing in creative thinkers and problem solvers who help people, communities, and the planet flourish.
0:11.1	More information is available at Hewlett.org.
0:14.6	You're listening to Shortwave from NPR.
0:19.6	Hey, shortwavers, Regina Barber here.
0:21.8	Get excited because today we're talking about dinosaurs with science reporter Ari Daniel.
0:27.6	Hey, Ari.
0:28.2	Hi, Regina.
0:29.2	Okay, I have got a riddle for you.
0:31.6	Okay.
0:32.2	What do you get when a team of researchers walks onto a crocodile farm?
0:37.3	Hmm. An academic team crocodile farm. Hmm.
0:38.3	An academic team building exercise.
0:41.6	Perhaps one with teeth.
0:43.5	No, actually, the answer is a different way of thinking about the age of a dinosaur.
0:48.8	Yeah, I was not going to get that.
0:51.3	Yeah, fair enough.
0:52.0	It was kind of a trick question.
0:55.7	Okay, since you brought it up, though, Ari, I do want to know how have researchers traditionally, like, estimated how old a dinosaur
1:01.9	was? It's been a fairly simple process, according to Anusia Chin Sami Taran. She's a paleobiologist
1:08.7	at the University of Cape Town in South Africa.
1:11.3	She says you just take those fossilized bones and count up the growth rings.
	...

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