Tenontosaurus tilletti

Tenontosaurus tilletti was a medium-sized, early-diverging iguanodontian from western North America. Numerous skeletons make it one of the best-known dinosaurs of the Cloverly Formation. It combined a relatively small head and beaked mouth with a deep torso, strong limbs and a tail that accounted for more than half its body length. Associations with Deinonychus teeth and remains have made it central to debates about predator–prey interactions, although the fossil sites record feeding more securely than coordinated hunting.

Its fossils occur between approximately 115 and 108 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull was low and narrow, with a horny beak at the front and closely packed cheek teeth behind it. Long forelimbs and broad hands could support the body during slow movement, while robust hind limbs also permitted bipedal locomotion. Bundles of ossified tendons reinforced the spine and the very long, deep tail.

• Very long, deep tail reinforced by ossified tendons
• Beaked mouth with batteries of leaf-shaped cheek teeth
• Robust hind limbs and weight-bearing forelimbs
• Broad hands suited to facultative quadrupedal support
• Deep torso for processing fibrous plants

An American Museum of Natural History expedition found the first material in Montana in 1903. Barnum Brown collected additional Cloverly skeletons during the 1930s. John Ostrom named Tenontosaurus tilletti in 1970 from holotype AMNH 3040, honouring the Lloyd Tillett family, whose ranch supported Yale field crews.

Discovery credit: American Museum of Natural History field crews.

Naming authors: John H. Ostrom.

The Cloverly Formation preserves river floodplains, channels and seasonally dry woodland east of the young Rocky Mountain region. Tenontosaurus lived alongside Deinonychus, Sauropelta, small mammals, turtles and crocodyliforms.

Tenontosaurus cropped low vegetation and could probably switch between two-legged and four-legged movement. Several sites combine Tenontosaurus bones with Deinonychus teeth or remains, demonstrating scavenging or predation but not proving coordinated pack hunting. Herding and use of the tail as a weapon remain plausible but unconfirmed.

• Its tail made up more than half of its total body length.
• It is the most commonly recovered large dinosaur in much of the Cloverly Formation.
• The familiar Deinonychus–Tenontosaurus association occurs at more than one fossil site.
• The species honours the Tillett family of Wyoming.

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1. 01
   The Paleobiology Database

   Open source
2. 02
   Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana

   John H. Ostrom · Bulletin of the Peabody Museum of Natural History 35 · 1970

   Open source
3. 03
   Osteology of a near-complete skeleton of Tenontosaurus tilletti from the Cloverly Formation, Montana

   Jonathan P. Tennant · Journal of Vertebrate Paleontology 32(6), 1377–1404 · 2012

   Open source
4. 04
   Tenontosaurus tilletti

   American Museum of Natural History

   Open source