Dryptosaurus

Dryptosaurus (/ˌdrɪptoʊˈsɔːrəs/ DRIP-toh-SOR-əs; meaning "tearing lizard") is a genus of theropod dinosaur that lived in the present-day East Coast of the United States during the Late Cretaceous period. The type, and only, species, D. aquilunguis was described by Edward Drinker Cope in 1866 as Laelaps aquilunguis, however the genus name was preoccupied by a mite. As a result, Cope's rival in the Bone Wars, Othniel Marsh, replaced the genus name with Dryptosaurus. Dryptosaurus is known from a single, fragmentary skeleton including parts of the mandible (lower jaw), limbs, and vertebrae. These fossils were unearthed by fertilizer miners in New Jersey in rock layers of the New Egypt Formation. This formation dates to the late Maastrichtian stage of the Late Cretaceous, around 67 to 66 million years ago. Several other fragmentary remains have been assigned to Dryptosaurus, however their referral is uncertain.

Like other tyrannosaurs, Dryptosaurus was a bipedal carnivore with a long tail and elongated skull. Unlike other tyrannosaurs like Tyrannosaurus and Tarbosaurus, Dryptosaurus possessed large forelimbs ending in large claws and lithe hindlimbs. Size estimates place it at 7.5 metres (25 ft) in length and 756–1,500 kilograms (1,667–3,307 lb) in mass. The genus had ziphodont (sharp, blade-like, laterally compressed) dentition, dissimilar to that of larger tyrannosaurs.

Dryptosaurus is a member of Eutyrannosauria, the clade including Tyrannosauridae and tyrannosaurs like Nanotyrannus and Bistahieversor but excluding more basal tyrannosaurs like Dilong. This puts Dryptosaurus in an intermediate position between lithe, early tyrannosaurs and the large tyrannosaurids. However, some studies have also put it in its own family, Dryptosauridae, or in Nanotyrannidae. Dryptosaurus is one of few Cretaceous dinosaurs known from the Eastern United States. During the Late Cretaceous, North America was divided into two continents; Appalachia and Laramidia. The breakup of North America into these continents spurred the evolution of unique characteristics in Appalachian tyrannosaurs not observed in Laramidian tyrannosaurs. Fossils of Dryptosaurus are known from the marine New Egypt Formation where dinosaur bodies floated out to sea and became fossilized. Mosasaurs, fish, sharks, and other marine fauna are represented in this formation.