Utahraptor

Chapter • Meet the dinosaur

Overview

Utahraptor was the largest dromaeosaurid ever found — a heavyset cousin of Velociraptor and Deinonychus built on an entirely different scale. Adults reached roughly 4.5 to 7 metres in length, stood with the head about at the height of a tall person, and are estimated to have weighed between 280 and 800 kilograms. Everything about the skeleton speaks of power rather than pure speed: thick hind limbs, a broad pelvis, stout arms tipped with long curved hand claws, and a stiffened tail braced by bundles of bony tendons that worked as a counterbalance. On the second toe of each foot sat the famous sickle claw, its bone core over 20 centimetres long and, with its horny sheath, longer still. No skin impressions are known from Utahraptor itself, but because feathers are documented in several close relatives — Velociraptor even preserves quill knobs on its forearm — modern reconstructions show it clothed in a shaggy feather coat with feathered arms rather than bare scales.

Chapter • Where it lived

Habitat

Utahraptor lived roughly 139–135 million years ago, in the Barremian stage of the Early Cretaceous, in what is now eastern Utah, USA. Every confirmed specimen comes from the Yellow Cat Member of the Cedar Mountain Formation, notably the Gaston Quarry and Dalton Wells sites near Arches National Park, and the enormous Stikes Quarry block. The setting was a semi-arid lowland of braided rivers, seasonal lakes and floodplains, with conifers, ferns and cycads — flowering plants had not yet taken over. Utahraptor shared this landscape with the heavily armoured Gastonia, iguanodontians such as Iguanacolossus and Hippodraco, the long-necked Moabosaurus and small early mammals.

Chapter • Family life

Breeding

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy