Terrific Tetanurae! #3 Tanycolagreus

Hi everyone! I would like to welcome you to Terrific Tetanurae! #3, a series in which I will explore the weird and wonderful dinosaurs which make up the clade tetanurae! Thanks for reading, and I hope you enjoy the article!

Hi everyone, welcome to Terrific Tetanurae! This week the dinosaur in question is Tanycolagreus topwilsoni, an obscure coelurid  from the Morrison Formation. It all began it 1995 when WPL (Western Paleontology Laboratories Inc.) uncovered a partial dinosaur skeleton from Bone Cabin Quarry in Wyoming. The site is part of the Salt Wash Member of the Morrison Formation, and the site dates to the Kimmeridgian epoch of the Jurassic period, around 153 million years ago. Originally considered a species of Coelurus, Tanycolagreus was only described as a separate genus by Kenneth Carpenter et. al. in 2005. The taxonomy of the animal is dubious, as with the rest of coeluridae, which has been considered a group within compsognathidae, tyrannosauroidae, and everything in-between. During the late Jurassic period, the Bone Cabin Quarry was a wet environment and many different aquatic animals lived there. Tanycolagreus may have preyed upon this animals, but as of now, we have no fossil evidence of this behavior. It was most likely a primarily terrestrial carnivore, preying on small to medium sized animals. Tanycolagreus was actually fairly large for a coelurid, the holotype an estimated 11 feet long. A partial pre maxilla from the Cleveland-Lloyd Quarry also assigned to Tanycolagreus is estimated to have come from an individual around 13 feet long. Tanycolagreus was most likely a secondary predator, surviving in the shadows of the macro-predatory allosaurids and megalosaurids. Eventually, relatives of Tanycolagreus would come out of the shadows and evolve into one of the most diverse groups of vertebrates ever, the birds.

Tanycolagreus by the author

Tanycolagreus by the author. Pencils on paper, 2015.


1. Miles, C.A., Carpenter, K. and Cloward, K.C.,1998, “A new skeleton of Coelurus fragilis from the Morrison Formation of Wyoming”, Journal of Vertebrate Paleontology 18(3): 64A

2.  Carpenter, K., Miles, C.A., and Cloward, K.C. 2005. “New small theropod from the Upper Jurassic Morrison Formation of Wyoming.” The Carnivorous Dinosaurs. Indiana University Press, Bloomington:  23-48 3. Senter, P. 2007. “Appendix.” Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329


  1. Tanycolagreus is interesting for me because there are very few medium-sized predators from the Morrison Formation. You have Allosaurus and Torvosaurus (and possibly Saurophaganax, which might be a separate species or an unusually large Allosaurus), both of which reached a maximum size of 35 feet, who were the top predators. Then you have the 20-foot Ceratosaurus, which was the only medium-sized predator present for a long time. Finally, you have the smaller coelurosaurs like Ornitholestes and Coelurus (one of my personal favorites). The discovery of Tanycolagreus fills in a hithertoo vacant ecological niche.


    1. I agree with you completely. As I stated in this post, Tanycolagreus probably hunted for small to medium sized terrestrial game. This is my personal opinion, but I think Tanycolagreus was the fox to Allosaurus’s lion of the jurassic. I also can’t help but wonder if Tanyoclagreus is a juvenile of Marshosaurus, which would make it a junior synonym.


  2. Actually, I was wondering if Marshosaurus is actually a juvenile Torvosaurus. Both belong to Megalosauridae, and both lived in the same area. However, according to current phylogenics, Marshosaurus is much more primitive than Torvosaurus. So far, very few remains of this animal have been found. Until more is discovered, I think that Marshosaurus will have a parenthetical question mark next to its name for the forseeable future.

    Liked by 1 person

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