Dryptosaurus

Chapter • Meet the dinosaur

Overview

Dryptosaurus was a medium-sized predatory dinosaur roughly 6–7.5 metres long that weighed around a tonne, possibly a little more. It walked on two powerful hind limbs with long, slender metatarsals, much like the later tyrannosaurids, but it also had something most of its relatives lacked: relatively long arms tipped with big, strongly curved claws. The largest hand claw measures about 20 centimetres along its outer curve, and it is exactly that claw that gave the animal its species name aquilunguis, 'eagle-clawed'. The skull is known only from scattered pieces, though the jaw fragments preserve teeth of clearly tyrannosauroid type. No skin or feather impressions are known for Dryptosaurus, but because several related tyrannosauroids preserve filamentous feathers, many researchers think Dryptosaurus may have had at least a partial feathery covering. The body was held horizontally with the tail as a counterweight — no dragging tail. The skeleton is a curious mosaic of primitive and advanced features. The hind limbs are long and slim, built for efficient striding, while the arms look more like those of older, more basal predatory dinosaurs. That mix makes Dryptosaurus an important window onto the predator fauna of Appalachia, the eastern island continent cut off from western North America by the Western Interior Seaway during the Late Cretaceous. While Tyrannosaurus rex was evolving in the west, more conservative tyrannosauroids persisted in the east. Dryptosaurus was a carnivore and probably the largest land predator in its ecosystem. With long arms and large claws it may have grabbed and held prey in a way that the tiny-armed Tyrannosaurus never could. Likely prey included duck-billed dinosaurs such as Hadrosaurus, along with smaller plant-eaters and carcasses washed up along the shore. Its actual hunting behaviour, however, is unknown: there are no bite marks or gut contents to tell us what it really ate. The discovery story is one of the most celebrated in American palaeontology. In 1866 a partial skeleton turned up in a marl pit near Barnsboro, Gloucester County, New Jersey, and Edward Drinker Cope described it that same year as Laelaps aquilunguis. The name Laelaps was already in use for a genus of mites, so Othniel Charles Marsh renamed the animal Dryptosaurus, 'tearing lizard', in 1877. Charles R. Knight's 1897 painting 'Leaping Laelaps' showed two of these animals airborne in mid-fight and became one of the first images ever to portray dinosaurs as fast, active creatures. The skeleton was redescribed by Stephen Brusatte, Roger Benson and Mark Norell in 2011, confirming Dryptosaurus as a tyrannosauroid.

Chapter • Where it lived

Habitat

Dryptosaurus lived during the Maastrichtian stage at the very end of the Cretaceous, roughly 68–66 million years ago, on the island continent of Appalachia. The holotype (ANSP 9995) was recovered in 1866 from a marl pit near Barnsboro, Gloucester County, New Jersey, in marine deposits usually referred to the New Egypt Formation. Being buried in marine sediment does not mean the animal lived at sea — the carcass was most likely carried offshore by a river. The landscape was a humid, subtropical coastal plain of river deltas, swamps and forests fringing the Western Interior Seaway.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy