Kingdom: Animalia
Phylum: Chordata
Class: Sauropsid
Superorder: Dinosauria
Order: Ornithischia
Suborder: Cerapoda
Infraorder: Ornithopoda
Family: Tenontosauridae
Genus: Tenontosaurus

This medium-sized ornithopod lived during the early to middle Cretaceous, and is known for its lack of facial adornment and extreme length of its tail. Tenontosaurus is a fairly unremarkable member of the Ornithopoda, but research into its skeleton has revealed details of the dinosaur reproductive timeline. The appearance of bones necessary for the laying of eggs in non-adult specimens indicates that sexual maturity was reached relatively early, possibly due to high adult mortality. This behaviour is found in mammals, and provides another piece of evidence that dinosaur physiology was not necessarily related to that of reptiles.

Type Species: Tenontosaurus tilletti

Ostrom, JH. (1970). Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana. Peabody Museum of Natural History Bulletin 35, pp. 235.

Locality:

Cloverly Formation, Wyoming/Montana, USA.

Scientific Resources:

Lee, AH; and Werning, S. (2008). Sexual maturity in growing dinosaurs does not fit reptilian growth models. Proceedings of the National Academy of Sciences, Vol. 105, No. 2, pp. 582-587.

Moreno, K; Carrano, MT; and Synder, R. (2006). Morphological changes in pedal phalanges through ornithopod dinosaur evolution: A biomechanical approach. Journal of Morphology, Vol. 268, Issue 1, pp. 50-63.

Forster, CA. (1990). Evidence for Juvenile Groups in the Ornithopod Dinosaur Tenontosaurus tilletti Ostrom. Journal of Paleontology, Vol. 64, No. 1, pp. 164-165.