Fossil Friday: Kayentachelys

Species: Kayentachelys aprix (Kah-yen-ta-kel-ees A-pricks)

What it means: Kayenta shell

Other species: none

Where I live: Arizona in the U.S.A.- The Kayenta formation

When to find me: The Early Jurassic period, about 196 million years ago.

My favorite food: Bugs, plants that grow along the riverbank, whatever I can snap at really! I’m an omnivore.

My neighborhood: The Kayenta formation used to be a tropical floodplain, a bit like African savannah today- but no grass or flowers. Ferns cover the open plains, dotted with islands of spiky cycad groves. Rivers crisscross the land with lush tree ferns, ginkgo trees, and conifers. Every year during the wet season the plains turn into a flooded marsh, but the hottest months bring no rain, and the rivers shrink until the plains are almost as dry as the great desert that lies to the north.

A few of my neighbors: I have to watch out for all sorts of predators like Dilophosaurus, Kayentavenator, Coelophysis (meat-eating dinosaurs), and crocodile cousins. More friendly neighbors are Sarahsaurus (an early sauropod), and Scutellosaurus (small armored dinosaur). I like to hang out on the riverbank with the frogs and the flying pterosaurs. There’s always a steady hum ofย  insects like beetles, dragonflies, an ancient cousin of the moth, and something called a snakefly.

Fun Facts:

  • There are two groups of modern turtles. Cryptodira- the group of turtles that can hide their heads inside their shells, and Pleurodira- turtles that tuck their necks sideways so their heads fit under the rim of their shells. Some say I am the oldest known Cryptodire, but others say I am not a direct relative to modern turtles at all! I look a lot like one though!
  • Using the place a critter is found in a name is pretty common. Kayenta + chelys (latin for a turtle or tortoise shell) = Turtle from the Kayenta Formation. Aprix is Greek for tight, and describes how all the bones in the base of the skull are fused.

Fossil Finds: Abundant, fragmentary remains of head, shell, and body.


Gaffney, E.S. and Jenkins Jr, F.A. (2010), The cranial morphology of Kayentachelys , an Early Jurassic cryptodire, and the early history of turtles. Acta Zoologica, 91: 335-368. doi:10.1111/j.1463-6395.2009.00439.x

Gaffney ES, Hutchison JH, Jenkins FA Jr, Meeker LJ. Modern turtle origins: the oldest known cryptodire. Science. 1987;237(4812):289โ€291. doi:10.1126/science.237.4812.289

Sterli, Juliana & Joyce, Walter. (2007). The cranial anatomy of the Early Jurassic turtle Kayentachelys aprix. Acta Palaeontologica Polonica. 52.

Joyce, Walter. (2009). Phylogenetic Relationships of Mesozoic Turtles. Bulletin of the Peabody Museum of Natural History. 48. 3-102. 10.3374/0079-032X(2007)48[3:PROMT]2.0.CO;2.

Cherepanov, Gennady. (2006). Ontogenesis and evolution of horny parts of the turtle shell. Fossil turtle research. Suppl. Russian J. Herpetology. 1. 19-33.

18 thoughts on “Fossil Friday: Kayentachelys

  1. Cool! ๐Ÿ˜€ I had never heard of the distinction between Pleurodira and Cryptodira before, that’s really interesting! Do modern turtles have that distinction too? Is kayentachelys related to the turtle-like critter on the banner?


    1. Pleurodira and Cryptodira are the two groups that make modern turtles today! At first paleontologists believed that Kayentachelys was the first official Cryptodire, and so proof that the modern group of turtles has been around for a shockingly long time, but later evidence showed that it actually wasn’t in the same group. It was something in between what is known as a Stem turtle, and true modern turtles. So, an almost-turtle lol ๐Ÿ˜€

      The turtle-ish thing on the homepage is Henodus, and not related to turtles at all! It is a placodont, marine reptiles of the Triassic that evolved turtle-like shells, and are speculated to be more closely related to plesiosaurs than turtles. ๐Ÿ™‚

      Liked by 1 person

  2. I cannot express how much I enjoy your work. Not only are your paintings delightful, but I am also pleased to see that you are increasingly devoting your attention to obscure species of prehistoric environments instad of the commonly-known species that everyone can name off of the tops of their heads. In many cases, I’ve never heard of these species until I saw one of your drawings. Keep up the great work!


    1. Thank you so much Jason! I’m glad you enjoy them, and I’m having so much fun discovering so many new creatures I’d never heard of before. I really like exploring the formations like this! It’ll be hard to determine which formation I’ll do next… ๐Ÿ˜€

      Liked by 1 person

  3. Thank you Angel! I often do quite a bit of research for these, so I’m going to be including my sources from now on. I’ll edit the ones I’ve already done to include the new information too.

    I think it’ll be helpful to know how many fossils are known of each critter. It really shows how much or how little we actually know about them. ๐Ÿ™‚

    As for who’s next, I think it’s about time one of the mammal-ish critters make an appearance. ๐Ÿ˜‰


  4. Not only is this prehistoric turtle review amazing, but the additions of fossil remains help out. I think Kayentachelys is an overlooked chelonid, and your resources really help out. What do you think might be next?


Leave a Reply

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

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

Facebook photo

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

Connecting to %s