Summary: The term “living fossil” is a bit controversial but does it fit the tuatara? Join Kiersten to find out.
For my hearing impaired followers, a complete transcript of this podcast follows the show notes on Podbean
Show Notes:
“New study shows modern tuatara are little changed from 190 million year old ancestors.” Harvard University Department of Organismic and Evolutionary Biology, March 2022. https://www.oeb.harvard.edu/news
Music written and performed by Katherine Camp
Transcript
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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
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Kiersten - Welcome to Ten Things I Like About… This is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
The sixth thing I like about the tuatara is how long they have lived. Just like another animal we have talked about, the coelacanth, the tuatara appears in the fossil record from way back in time. The first time we see the tuatara in the fossil record is during the Jurassic period. Now, of course, a certain book and movie series has made this a very popular time in Earth’s history, so you may be familiar with this time period. It is famous for being the age of dinosaurs, at least some of the most popular and recognizable dinosaurs.
The term living fossil has been tossed around in reference to the tuatara, as well as the coelacanth, but this term is controversial. It is quite the romantic phrase actually. To think that an animal is so well adapted to the world it lives in that is hasn’t changed since the first time it appeared on this planet is a notion that a lot of us want to believe, but is it true? The first major problem with this concept, is that there is no real definition of what makes an animal or plant a living fossil.
Charles Darwin coined the term “living fossil” in 1859. According to Darwin’s definition a living fossil is a species or group of species that is so little changed that it provides an insight into earlier, now extinct, forms of life. A living fossil can also be described as an organism that has remained relatively unchanged over millions of years, or one that has no, or very few, close surviving relatives.
It certainly sounds like we have stumbled on another controversy here. In the last episode we answered the question of whether the tuatara is a lizard or not. Spoiler here, listeners, if you haven’t heard the previous episode and you don’t want a spoiler to this question, stop listening now and go back and listen to last week’s episode. With that warning, let’s move on. We have established that tuatara are not lizards, they are reptiles but not lizards for various reasons. Shall we jump into the next controversial question then?
Are tuatara living fossils? Let’s look at Darwin’s definition first. How much have tuatara changed since they first appeared in the fossil record? A 2022 study from Harvard University’s Department of Organismic and Evolutionary Biology may give us some insight. Tuatara are the last remnant of the Rhynchocephalians. These reptiles peaked in abundance in the Jurassic period. Then they disappeared from the fossil record.
Two researchers were looking through the archives in the Harvard Museum of Comparative Zoology and came across something that had been sitting in the drawers for decades, a tuatara fossil. This fossil was discovered in northern Arizona in the Kayenta Formation of the United States in 1982. Professor Stephanie Pierce and postdoctoral fellow Tiago Simoes jumped into examining this forgotten fossil. They used micro-CT scans to examine the fossil in three dimension. Then they digitally pieced the puzzle together revealing a full unflattened skull. It greatly resembled the modern day tuatara. It had rows of interlocking teeth that extended directly from the bone and it had two holes behind the eyes, just like the modern day tuatara.
Pierce and Simoes named the fossil Navajoshenodon sani which means “old age” in the indigenous language of the Navajo. This fossil provides the first nearly complete skull of any fossil sphenodontine in the world. It also places the tuatara in the Late Triassic. They may be older than we thought.
So how does this help us determine the answer to the living fossil question? It does give support for both descriptions. The modern day tuatara is similar enough to the fossil that it gives us insight into a long dead relative, and it seems to have changed very little from the long ago fossil of a creature that roamed the planet with dinosaurs.
Unlike the coelacanth, which is definitely not a living fossil, maybe the tuatara is a living fossil. It is food for thought and that is one of the reasons I started this podcast.
I hope you will continue to think about this small living fossil controversy because it is my sixth favorite thing about the tuatara.
If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.
Join me next week for another exciting episode about the tuatara.
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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
