Sunday, February 17, 2013

Tenontosaurus: Beast of the Week

Tenontosaurus was a plant eating dinosaur that lived during the Early Cretaceous Period between 118 and 110 million years ago in what is now the United States of America.  Its remains have been found in several states including Montana, Oklahoma, Texas, Utah, Wyoming, and even on the east coast in Maryland.  It was a member of the ornithopod group of dinosaurs, and was close relatives with Iguanodon and Mantellisaurus, and like them could have walked on all fours, or on its hind legs depending on what suited it best.   Probably the most striking feature about this dinosaur was its tail which makes up for more than half of the animal's body length.  An adult Tenontosaurus was about twenty three feet long.

Tenontosaurus tilletti pairlife restoration by Christopher DiPiazza.  The male's display behavior and skin ornamentation are inspired by modern Green Iguanas.

Tenontosaurus was one of the few dinosaurs in which medullary bone was discovered.  Medullary bone (mentioned this past week in my Valentine's Day post) is a special kind of material inside of a bone that stores calcium for egg production.  It's present only in females and is known to be in modern birds but has also been discovered in extinct dinosaurs like Tyrannosaurus and Allosaurus as well.  Unlike Tyrannosaurus and Allosaurus, however, Tenontosaurus is considered an ornithiscian dinosaur and therefore not as closely related to birds as the other two (theropods) making the fact that it could produce the medullary tissue especially interesting.  Even more interesting, the Tenontosaurus specimen that was found to have this medullary bone, which is only produced when the animal is laying or about to lay eggs, was not fully grown when it died.  This shows that Tenontosaurus was sexually mature before reaching full size. 

Tenontosaurus skeletal mount on display at the American Museum of Natural History.

 There is a famous fossil of a Tenontosaurus with chew marks from the meat-eating dinosaur, Deinonychus on its bones.  There were actual remains of Deinonychus found nearby as well.  This led many to believe that the meat eating dinosaurs had actually killed the plant eater as a pack, some being killed, themselves, as the bigger Tenontosaurus tried to defend itself.  Not all scientists agree with this, however, saying the Tenontosaurus could have been scavenged by Deinonychus that had killed each other while fighting over its remains.  Either way it's because of this discovery that has made poor Tenontosaurus the poster child for being Deinonychus food.  Seriously, if you google-image search "Tenontosaurus" more than half of the pictures will be of it getting attacked or eaten by a pack of Deinonychus.  While dinosaurs fighting is always exciting, to me, Tenontosaurus was so much more interesting than just prey for some meat-eater!

That's it for this week!  As always if you have a request or just feel like saying how awesome of a job you think I am doing at this feel free to do so on our facebook page


Forster, C.A. (1984). "The paleoecology of the ornithopod dinosaur Tenontosaurus tilletti from the Cloverly Formation, Big Horn Basin of Wyoming and Montana." The Mosasaur, 2: 151–163.

Lee, Andrew H.; and Werning, Sarah (2008). "Sexual maturity in growing dinosaurs does not fit reptilian growth models". Proceedings of the National Academy of Sciences 105 (2): 582–587. Bibcode 2008PNAS..105..582L. doi:10.1073/pnas.0708903105. PMC 2206579. PMID 18195356.

Roach, B. T.; D. L. Brinkman (2007). "A reevaluation of cooperative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs". Bulletin of the Peabody Museum of Natural History 48 (1): 103–138. doi:10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2.


  1. "Its considered an ornithopod dinosaur so its related to Parasaurolophus and Heterdontosaurus to a certain degree"

    Wouldn't Iguanodon, or even Hypsilophodon have been a better well-known somewhat-near-reletive to use than Heterodontosaurs, which is not an ornithopod?

    1. You are correct. Tenontosaurus actually is considered a sort of Iguanodontid last I knew. Heterdontosaurus is also considered not a true ornithopod but a different basal ornithiscian (I lump it in with them on our list of animals page sorry) but it and Parasaurolophus are the closest related animals to Tenontosaurus that have been reviewed on this site so far. Its why i said "to a degree". In the future when I review Iguanodon or Hypsilophodon (or something else more closely related), Tenontosaurus will be mentioned of course.