Tenontosaurus is a genus of extinct ornithopod dinosaur that lived 115 to 108 million years ago. Earlier, it was thought to be a ‘hypsilophodont,’ which is no longer considered a clade. It is now considered a primitive iguanodont.

History and Discovery

The first ever Tenontosaurus fossil was found, in 1903, in Montana by an American Museum of Natural History team. During the 1930s, search efforts resulted in excavating 18 more specimens, while 4 were unearthed in the 1940s. Yale University, in the 1960s, started a long-scale digging program, led by John Ostrom, in the Big Horn Basin area in Montana and Wyoming. The expedition managed to unearth 40 new samples. After the 1970s, several Tenontosaurus specimens were reported from several geological formations, such as – Arundel Formation of Maryland, Cedar Mountain Formation of Utah, Wayan Formation of Idaho, Paluxy Formation of Texas and Antlers Formation in Oklahoma.

Physical Description

Tenontosaurus had a flexible, long neck; and a horny beak. It had a laterally compressed skull. Tenontosaurus had strong, tightly fitted teeth. But there were no teeth on the front end of its mouth. Their forelimbs were shorter than the hindlimbs. They had a long, broad, stiffened tail covering around two-thirds of its length. It was supported by a network of strong bony tendons. Ossified tendons were also there in its hips and back.

Etymology

The name Tenontosaurus is referential of its tendons. At the time of discovery, it was called ‘Tenantosaurus,’ an informal name given by Barnum Brown. However, its present scientifically recognized name Tenontosaurus was coined by John Ostrom.

Adaptation and Behavior

They were a highly adaptable animal. When Tenontosaurus first appeared in Wyoming and Montana, they lived in dry, semi-arid habitat with seasonal rainfall and periodic droughts. In a few million years, the environment became sub-tropical to tropical, with swampy inlets, flood plains and river deltas.

Even though it probably did most of its walking and running on its back legs, Tenontosaurus also had very strong front legs with short and wide feet. It probably used them to walk quadrupedally (on all four limbs) to browse low vegetation. Their diet consisted of ferns, cycads and primitive flowering plants. Some accounts suggest that their also fed on fruits.

Unlike other iguanodontians, T. tilletti grew quite fast early in life and also during sub-adult ontogenesis. However, the growth rate decreased in the years approaching maturity.

Interesting Facts

• One fossil evidence suggests they lived in packs (probably family groups).
• This animal was featured in paleontology-based television series Jurassic Fight Club.
• Tenontosaurus has been a prominent figure in several toy-lines.