Tenontosaurus

Tenontosaurus tilletti

• USA

• Tenontosaurus tilletti Ostrom, 1970
• Tenontosaurus dossi Winkler, Murry & Jacobs, 1997

Tenontosaurus ( "lizard with tendons " ) was a dinosaur from the group of Iguanodontia, which was widespread in the Lower Cretaceous ( Aptian to middle Albian ) in North America.

Two species have been described, the type species Tenontosaurus tilletti were found from the about 27 skeletons in the Cloverly Formation in Montana and Wyoming, and the Paluxy Formation in Texas and Tenontosaurus dossi of the skulls and skeletons of various individuals from the Twin Mountain Formation originate in Texas. At several places a copy of Tenontosaurus were recovered along with several copies of the predatory dinosaur Deinonychus.

Features

Tenontosaurus was a medium-sized Iguanodontide, reaching a length of about seven meters, with its long tail accounting for almost two-thirds of the total length. The Praedentale, an only bird Beck dinosaurs ( Ornithischia ) present additional bone in the lower jaw in front of the dentary is seen from the side wedge-shaped when viewed from above a horseshoe. On the Praedentale be tooth-like outgrowths were. It resembled the Praedentale more basal Euornithopoda. The Dental had twelve teeth.

Tenontosaurus had 12 cervical, 16 trunk, 5 sacral, and 60 to 65 caudal vertebrae. The cervical vertebrae were slightly opisthocoel (on the back concave), the spinous processes were short. In adult forms of the Wirbelcentra of the sacrum and their ribs were grown together, yet separately in younger. The located towards the body ( proximal ) caudal vertebrae had short and wide and narrow vertebral spinous low altitude were bent forward. The further back vertebrae were longer.

His front legs held Tenontosaurus bent primarily. The metacarpal bones were flattened at the top and arranged in a splayed shape. The forefoot has the Phalangenformel 2.3.3.1 (? 2) .1 (? 2), the hind 2.3.5.5.0. Tenontosaurus therefore had five forward- and rear four toes. The fifth metatarsal bone was reduced to a short single bone. The Zehenendglieder were narrow and pointed.

System

Tenontosaurus was originally assigned to the Hypsilophodontidae, a taxon that is now regarded as paraphyletic. Currently Tenontosaurus is considered the most basal standing Iguanodontide. Of the two types Tenontosaurus dossi is the more original, as it comes from the Aptian ( Tenontosaurus tilletti from the late Aptian to middle Albian ) and still had one tooth on the premaxilla.