Temporal range: Early Cretaceous
A restoration of Tenontosaurus tilletti
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
clade: Dinosauria
Superorder: Ornithopoda
Genus: Tenontosaurus
Ostrom, 1970
Species: T. tilletti
Binomial name
Tenontosaurus tilletti
Ostrom, 1970

Tenontosaurus was an Ornithopod that lived during the Early Cretaceous period in North America. It was mostly prey for Deinonychus and Acrocanthosaurus.

The three long, sharp claws on its hands would have enabled Tenontosaurus to swipe at a predator.


It was about 6.5 to 8 meters (21 to 26 ft) long and 3 meters (10 ft) high in a bipedal stance, with a mass of somewhere between 1 to 2 tonnes (1 to 2 short tons). It had an unusually long, broad tail, which like its back was stiffened with a network of bony tendons.


The first Tenontosaurus fossil was found in Big Horn County, Montana by an American Museum of Natural History (AMNH) expedition in 1903. Subsequent digs in the same area during the 1930s unearthed 18 more specimens, and four specimens were found during the 1940s. Despite the large number of fossil specimens, the animal was not named or scientifically described during this time, though Barnum Brown of the AMNH gave it the informal name "Tenantosaurus", "sinew lizard", in reference to the extensive system of stiffening tendons in its back and tail.

During the 1960s, Yale University began an extensive, long-term dig in the Big Horn Basin area (Cloverly Formation) of Montana and Wyoming. The expedition was led by John Ostrom, whose team discovered more than 40 new specimens. Following his expedition, Ostrom became the first to describe and name the animal, calling it Tenontosaurus, a slight variation in spelling of Brown's informal name.

Since 1970, many more Tenontosaurus specimens have been reported, both from the Cloverly and other geological formations, including the Antlers Formation in Oklahoma, Paluxy Formation of Texas, Wayan Formation of Idaho, Cedar Mountain Formation of Utah, and Arundel Formation of Maryland.


The cladogram below follows an analysis by Butler et al, 2011.

   T. tilletti
   T. dossi
   Ankylopollexia (including Iguanodon, hadrosaurids, and others)


Plant life in the Tenontosaurus ecosystem was likely dominated by ferns and tree ferns, cycads, and possibly primitive flowering plants. Larger plants and trees were represented by gymnosperms, such as conifer and ginkgo trees. Tenontosaurus was a low browser, and an adult would have had a maximum browsing height of about 3 meters (10 ft) if it adopted a bipedal stance. This restricted Tenontosaurus, especially juveniles, to eating low-growing ferns and shrubs. Its powerful, U-shaped beak and the angled cutting surfaces of its teeth, however, meant it was not limited to which part of the plant it consumed. Leaves, wood, and even fruit may have formed part of its diet.

Teeth and a number of skeletons belonging to the carnivorous theropod Deinonychus have often been discovered associated with Tenontosaurus tilletti remains. Tenontosaurus specimens have been found at over 50 sites, and 14 of those also contain Deinonychus remains. According to one 1995 study, only six sites containing Deinonychus fossils contain no trace of Tenontosaurus, and Deinonychus remains are only rarely found associated with other potential prey, like Sauropelta. In all, 20% of Tenontosaurus fossils are found in close proximity to Deinonychus, and several scientists have suggested that this implies Deinonychus was the major predator of Tenontosaurus. Adult Deinonychus, however, were much smaller than adult Tenontosaurus, and it is unlikely a single Deinonychus would have been capable of attacking a fully grown Tenontosaurus. While some scientists have suggested that Deinonychus must therefore have been a pack hunter, this view has been challenged based on both a supposed lack of evidence for coordinated hunting (rather than mobbing behavior as in most modern birds and reptiles, though crocodilians have been documented to hunt cooperatively on occasion) as well as evidence that Deinonychus may have been cannibalizing each other, as well as the Tenontosaurus, in a feeding frenzy.[7] It is likely that Deinonychus favored juvenile Tenontosaurus, and that when Tenontosaurus reached a certain size, it passed out of range as a food source for the small theropods, though they may have scavenged larger individuals. The fact that most Tenontosaurus remains found with Deinonychus are half-grown individuals supports this view. It also lived in the same area as the large carnivorous dinosaur Acrocanthosaurus.


Throughout the Cloverly Formation, Tenontosaurus is by far the most common vertebrate, five times more abundant than the next most common, the ankylosaur Sauropelta. In the arid Little Sheep Mudstone Member, Tenontosaurus is the only herbivorous dinosaur, and it shared its environment with the common predator Deinonychus as well as an indeterminate species of allosauroid theropod and goniopholid crocodile. After the major climate shift at the beginning of the Himes Member in the mid-Albian age, several more dinosaurs entered the region, including the less common ornithopod Zephyrosaurus, the oviraptorosaur Microvenator, and an indeterminate species of titanosauriform sauropod and ornithomimid. The ecological community in the tropical stage also included the small mammal Gobiconodon, turtles such as Glyptops, and species of lungfish.

The ecological community was similar in other regions, with dinosaurs like Tenontosaurus and Deinonychus as the most common large vertebrates. The Antlers Formation stretches from southwest Arkansas through southeastern Oklahoma and into northeastern Texas. This geological formation has not been dated radiometrically. Scientists have used biostratigraphic data and the fact that it shares several of the same genera as the Trinity Group of Texas, to surmise that this formation was laid down during the Albian stage of the Early Cretaceous Period, approximately 110 mya. The area preserved in this formation was a large floodplain that drained into a shallow inland sea. Several million years later, this sea would expand to the north, becoming the Western Interior Seaway and dividing North America in two for nearly the entire Late Cretaceous period. The paleoenvironment of the Antlers Formation consisted of tropical or sub-tropical forests, floodplains, river deltas, coastal swamps, bayous and lagoons, probably similar to that of modern-day Louisiana.[13][14] In the Antlers Formation in what is now Oklahoma, Tenontosaurus and Deinonychus shared their paleoenvironment with other dinosaurs, such as the sauropods Astrodon (Pleurocoelus) and Sauroposeidon proteles, and the carnosaur Acrocanthosaurus atokensis, which was likely the apex predator in this region. The most common dinosaur in the paleoenvironment preserved in this formation is Tenontosaurus. Other vertebrates present at the time of Tenontosaurus included the amphibian Albanerpeton arthridion, the reptiles Atokasaurus metarsiodonand Ptilotodon wilsoni, the crurotarsan reptile Bernissartia, the cartilaginous fish Hybodus buderi and Lissodus anitae, the ray-finned fish Gyronchus dumblei, the crocodilian Goniopholis, and the turtles Glyptops and Naomichelys.[17][18] Possible indeterminate bird remains are also known from the Antlers Formation. The fossil evidence suggests that the gar Lepisosteus was the most common vertebrate in this region. The early mammals known from this region include Atokatherium boreni and Paracimexomys crossi.

In Popular Culture[]

Acrocantosaurus vs Tenontosaurus2

A Tenontosaurus being attacked by an Acrocanthosaurus

  • Tenontosaurus appeared in Jurassic Fight Club where a pack of Deinonychus ambushed a herd and seperated one away to kill.
  • Tenontosaurus appears in Monsters Ressurected where they are being hunted by Deinonychus and Acrocanthosaurus.
  • In Jurassic Park I the comic, Dr. Alan Grant and Dr. Ellie Sattler had found Tenontosaurus fossils and Dr. Grant theorizes that these bones were the last meal of a fossilised pack of Velociraptor (which is actually a reclassified Deinonychus in this comic series) that they had just uncovered.
  • Tenontosaurus was planned to appear in the game Jurassic Park: Operation Genesis. For unknown reasons, the development of Tenontosaurus was terminated.
  • In the Jurassic Park novel, Alan Grant mentions Tenontosaurus when he is explaining to Ian Malcolm about coordinated attacking behavior in raptors. He states that it would be one of the prey items that Velociraptor (reclassified Deinonychus in the novels) would hunt and kill.
  • Tenontosaurus will be in Jurassic World: Alive. It inaccurately has a much shorter tail than in life.
  • "Tenontosaurus" will be in an upcoming game, "The Mesocene: Ecosystems". It is depicted more accurately with thick-musculature, a speculative tail hump, and a colorscheme inspired by the Blue Iguana.

Tenontosaurus is one of the dinosaurs in The Isle, The Image Beside This Text Is The Isle's Own Tenontosaurus.

Tenontosaurus (The Mesocene- Ecosystems)

The Mesocene: Ecosystems' very own Tenontosaurus!

Tenontosaurus is one of the dinosaurs in The Mesocene: Ecosystems, The Image Beside This Text Is The Mesocene's Own Tenontosaurus.