Camptosaurus dispar

Camptosaurus dispar was a medium-sized iguanodontian that lived across the floodplains of western North America during the Late Jurassic. Its deep skull, keratin-covered beak and closely packed ridged cheek teeth formed an effective plant-processing system, although it lacked the highly specialized dental batteries of later hadrosaurs. The forelimbs were shorter than the hind limbs but strongly built, so adults could probably move and feed on all fours while retaining the ability to rise or travel bipedally. Several partial skeletons and skulls make C. dispar anatomically well known, but the genus also has a complicated history: fossils once combined in museum mounts came from different individuals, and a skull long used in reconstructions was later recognized as the separate dinosaur Theiophytalia.

Its fossils occur between approximately 157 and 145 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull was relatively low and deep, with a toothless beak at the front and rows of ridged cheek teeth behind it. Its torso was broad, the pelvis and hind limbs were robust, and a long heavy tail balanced the body. Shorter but sturdy forelimbs could support weight, while the hands retained separate fingers rather than the compact hoof-like structure of later hadrosaurs. The animal's habitual posture remains debated, but its skeleton is compatible with both bipedal and quadrupedal movement rather than a permanently upright kangaroo-like stance.

• Deep beaked skull suited to cropping vegetation
• Closely packed cheek teeth with strong enamel ridges
• Broad torso with a robust pelvis
• Powerful hind limbs longer than the forelimbs
• Sturdy forelimbs capable of supporting body weight
• Long muscular tail balancing the trunk

William Harlow Reed found the first material at Quarry 13 near Como Bluff, Wyoming, in 1879 while collecting for Othniel Charles Marsh. Marsh named it Camptonotus dispar that year, then replaced the genus name with Camptosaurus in 1885 because Camptonotus had already been used for an insect. Additional Quarry 13 fossils were collected in the following years. After Marsh's death, important material passed to the Smithsonian, where Charles W. Gilmore prepared a detailed osteological revision and a composite mount in the early twentieth century. Gilmore's work remains a major historical record, although modern studies have separated several species and specimens once placed in Camptosaurus.

Discovery credit: William Harlow Reed.

Naming authors: Othniel Charles Marsh.

Camptosaurus lived on the river-fed floodplains and seasonally dry landscapes recorded by the Morrison Formation. Ferns, cycads, conifers and other plants formed a varied herbivore food supply. It shared these environments with sauropods such as Diplodocus, Apatosaurus and Brachiosaurus, armored dinosaurs including Stegosaurus, and predators such as Allosaurus and Ceratosaurus. The map marker represents the broad Como Bluff fossil region rather than the precise historic quarry face.

Its beak cropped plants and the cheek teeth sliced and crushed food before swallowing. Limb proportions suggest that it could feed or walk on four limbs and also move on the hind limbs, but the frequency and speed of each gait are not directly preserved. The tail was a counterbalance rather than a ground-dragging prop. No secure nest, herd structure or display behaviour is known specifically for C. dispar.

• It was first called Camptonotus, but that genus name already belonged to a cricket relative.
• The name Camptosaurus refers to flexibility rather than a permanently bent body.
• A skull once mounted and illustrated as Camptosaurus was later named Theiophytalia kerri.
• William Harlow Reed collected important fossils from the famous Como Bluff quarries.
• Its body plan combines powerful hind limbs with forelimbs sturdy enough to bear weight.

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1. 01
   Osteology of the Jurassic reptile Camptosaurus, with a revision of the species of the genus, and descriptions of two new species

   Charles W. Gilmore · Proceedings of the United States National Museum 36(1666), 197-332 · 1909

   Open source
2. 02
   Camptosaurus dispar specimen record

   Smithsonian National Museum of Natural History

   Open source
3. 03
   Camptosaurus dispar skeletal mount, United States National Museum

   Smithsonian Institution Archives

   Open source