Fossil Friday: Coelophysis

Species: Coelophysis kayentakatae (See-loh-fy-sis Kah-yen-tah-kah-tay)

What it means: Hollow form

Other species: Coelophysis bauri (type), Coelophysis rhodesiensis

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: Meat! I’m a carnivore.

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: Sarahsaurus (an early sauropod) and Scelidosaurus (armored dinosaur) are some tough neighbors. We don’t talk much. But if I’m lucky, little Scutellosaurus (small armored dinosaur) might join me for lunch. Dilophosaurus is the biggest carnivore around, but Kayentavenator (smaller meat-eater) are happy to share a few leftovers or join me on a quick chase after frogs, turtles, or a crocodile cousin or two. They like to stay close to the rivers. A long-tailed pterosaur patrols the skies for insects like beetles, dragonflies, an ancient cousin of the moth, and something called a snakefly.

Fun Facts:

  • My brother and sister Coelophysis have been running around here since the Triassic period! (technically different species of Coelophysis, but still, same genus)
  • I’m also known by the name Syntarsus, because it can be hard to figure out what bones are supposed to look like when they’re squashed by time, or broken before they’re fossilized. It was later determined that what appeared to make the bones unique from Coelophysis were really just distortion, so the name Syntarsus is no longer used.
  • When I was first discovered, some thought I might be a young Dilophosaurus because I have a double crest like the big guy, but they quickly determined that I was not because just like human children, young dinosaurs have bones that still have soft areas with room to grow. All my bones were ossified, and could not grow anymore.
  • The name Coelophysis comes from the Greek koilos (hollow) and physis (form). Kayentakatae is in honor of Dr. Kathleen Smith, who was often called “Kayenta Kay” for her work in the Kayenta formation, including her involvement in the discovery of the type specimen for C. kayentakatae.

Fossil Finds: Remains of at least three semi-articulated individuals that died in the same time and place, so that the bones are intertwined with each other.


Rowe, (1989). A new species of the theropod dinosaur Syntarsus from the Early Jurassic Kayenta Formation of Arizona. Journal of Vertebrate Paleontology. 9, 125-136.

Bristowe, A. & Raath, M.A. (2004). “A juvenile coelophysoid skull from the Early Jurassic of Zimbabwe, and the synonymy of Coelophysis and Syntarsus“. Palaeontologia Africana40: 31–41

17 thoughts on “Fossil Friday: Coelophysis

  1. Very interesting. The tropical floodplains must have been an amazing ecosystem back then with many diverse forms of life that never left fossils.


    1. Hi, thank you for stopping by! 😀

      The great thing about floodplains is that they are an ideal habitat for preserving fossils! Not as good as an anoxic lake like the Solnholfen formation in Germany, but still pretty good as far as preservation goes! Every year there is seasonal flooding when the rains come, burying everything in layers of silt and mud. Some of the things buried would be what scattered bones are still left from the dry season, while others might be creatures that drowned in the seasonal marsh, or otherwise where quickly lost and buried in the flooded plain.

      Larger animals may get partially covered in silt, but not covered enough when the dry season came and dried up the marsh, so we only have a fragmentary fossils of certain animals. Scelidosaurus is an example of one of these. The only reason we can guess that Scelidosaurus even lived in the Kayenta formation are the armor scutes found. But that’s pretty much all there is known about it. Most Scelidosaurus fossils are from Europe. Armored dinosaurs have a tendency to flip upside down in water, so perhaps a few were surprised by flashfloods while crossing a river, and only the armor scutes were buried in silt before the dry season came and left the rest of it exposed for scavengers. Or perhaps Scelidosaurus really only came to the floodplains during the dry season, and so the only bones still left when the floodwaters buried everything where the hard scutes. Who knows? It’s fun to guess though. 😀

      The seasonal marsh is great for preserving all the little stuff though, so in the Kayenta formation there are even fossils of tiny aquatic organisms. 🙂

      The tough part is finding the research papers describing the fossils! Everyone wants to publish a paper on dinosaurs, but it’s much harder to find and interpret any research on everything else in the environment. 🙂


  2. Thank you for stopping by Angel, I hope your sister had a good birthday. 🙂

    I’m trying to keep these Friday posts brief, because that is how I can publish every week while still making progress on the books. That said, many of the papers I read in researching Coelophysis k. used the name Syntarsus k., so that’s the name I mentioned. I only read about the insect on Wikipedia, so even though it was a reason not to use Syntarsus for the dinosaur anymore, the papers I came across talked more about “Syntarsus” being synonymous with Coelophysis, and didn’t mention the insect. A few referenced Megapnosaurus in passing, but I mentioned the more commonly used name Syntarsus.

    If anyone ever wants to find out more, Wikipedia is a great place to start for further research. 🙂 The purpose for this site is to be a jumping off point. Perhaps people can find out about creatures they never knew about, and do further research elsewhere if they so wish.

    Coelophysis will not be added to the shop until I get to the Triassic, which may take a while. These Friday posts are just to get a nice overview on particular formations, and are not official characters in the shop (except for the ones that actually are lol ).


    1. I’m glad you agree on one of my points. Also my sister had a good birthday, and her party was yesterday. I can see that you’ve got book progress to make, so I am okay with brief weekly blog posts. Anyway, good job with focusing on the Jurassic side of Coelophysis.


  3. Okay, a few things to mention:
    Base the PPS Coelophysis of off the type species C. bauri once added (probably under the name Cole)Yes, I know Coelophysis was known from the Jurassic, but it’s more famous for being a Triassic dinosaur. Also, Syntarsus was no longer used once it was found out that an insect had already occupied the name. Therefore, Megapnosaurus was used until it was found out to actually be a Coelophysis species. I just want to say to not do specific posts for secondary species. Also, can you please mention the type species in here?
    That was just my opinion on this. Also, two days ago was my sister’s birthday.


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