Dryptosaurus
Encyclopedia
Dryptosaurus was a genus
of primitive tyrannosaur that lived in Eastern North America
during the middle Maastrichtian
stage of the Late Cretaceous
period. Although largely unknown now outside of academic circles, a famous painting of the genus by Charles R. Knight
made it one of the more widely known dinosaurs of its time, in spite of its poor fossil
record. Its specific name aquilunguis is Latin for "having claws like an eagle's".
, Dryptosaurus seems to have had relatively long arms compared to, for example, Tyrannosaurus
, and the hands are believed to have had three fingers. Each of these fingers was tipped by a talonlike 8 inch claw. These claws lend a meaning for the type species
aquilunguis: eagle-clawed.
In 1866, an incomplete skeleton (ANSP
9995) was found in New Jersey
by quarry workers in rock belonging to the upper part of the New Egypt Formation. Paleontologist E.D. Cope
described the remains, naming the creature "Lælaps" ("storm wind", after the dog in Greek mythology
that never failed to catch what it was hunting). Lælaps became one of the first dinosaurs described from North America
(following Hadrosaurus
, Aublysodon
and Trachodon
). Subsequently, it was discovered that the name Lælaps had already been given to a genus of mite
, and Cope's lifelong rival O.C. Marsh
changed the name in 1877 to Dryptosaurus.
During the 19th century, numerous theropod species in North America were assigned to the genus Dryptosaurus (often as Lælaps or Laelaps), only to be reclassified. Only one potential second species is sometimes recognized today, D. macropus, known from a partial hind limb found in the Navesink Formation
(probably roughly equivalent to the New Eagle Formation in time). Joseph Leidy
originally referred the specimen to Coelosaurus. Cope later recognized it as a distinct species, referring to it as Lælaps macropus, differing from the specimen now known as Dryptosaurus by its longer toes. Subsequently, most scientists had concluded that it probably belonged to Coelosaurus after all, but in 2004 paleontologist Thomas R. Holtz listed it as an indeterminate tyrannosauroid, possibly referable to the genus Dryptosaurus.
in 2005. During that time Dryptosaurus was classified in a number of theropod families. Originally considered a megalosaurid by Cope, it was later assigned to its own family (Dryptosauridae) by Marsh, and later found (through phylogenetic studies of the 1990s) to be a coelurosaur
, though its exact placement within that group remained uncertain. The discovery of the closely related (and more complete) Appalachiosaurus made it clear that Dryptosaurus was a primitive tyrannosauroid
.
The fossil material assigned to Dryptosaurus was reviewed by Ken Carpenter
in 1997 in light of the many different theropods discovered since Cope's day. He felt that due to some unusual features it couldn't be placed in any existing family and warranted placement in its own family, Dryptosauridae.
Another dubious species was Laelaps trihedrodon by Cope in 1877. Although the type specimen included a partial dentary, all material—except for a collection of five damaged partial tooth crowns (AMNH 5780)—has been lost. AMNH 5780 has many features in common with Allosaurus and is probably referable to that genus. However some of the Allosaurus-like characters of the tooth are primitive to theropods as a whole and may have been present in the less-studied or poorly preserved [Morrison Formation theropod species. Consequently the synonymization of L. trihedrodon with Allosaurus is tentative, despite its high likelihood.
Although certainly a carnivore, the paucity of known Cretaceous East Coast dinosaurs make ascertaining the specific diet of Dryptosaurus difficult. Hadrosaurid
s are known from the same time and place as Dryptosaurus, the island continent of Appalachia
, and they may have been a prominent part of its diet. Nodosaurs were also present, although less likely to be hunted due to their armor plating.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of primitive tyrannosaur that lived in Eastern North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
during the middle Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
period. Although largely unknown now outside of academic circles, a famous painting of the genus by Charles R. Knight
Charles R. Knight
Charles Robert Knight was an American artist best known for his influential paintings of dinosaurs and other prehistoric animals...
made it one of the more widely known dinosaurs of its time, in spite of its poor fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
record. Its specific name aquilunguis is Latin for "having claws like an eagle's".
Description
Dryptosaurus is estimated to have been 7.5 metres (24.6 ft) long and to have weighed 1.5 metric tons (1.7 ST), although this is based on partial remains of one individual. Like its relative EotyrannusEotyrannus
Eotyrannus was a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom...
, Dryptosaurus seems to have had relatively long arms compared to, for example, Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
, and the hands are believed to have had three fingers. Each of these fingers was tipped by a talonlike 8 inch claw. These claws lend a meaning for the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
aquilunguis: eagle-clawed.
Discovery and species
Academy of Natural Sciences
The Academy of Natural Sciences of Drexel University, formerly Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the New World...
9995) was found in New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
by quarry workers in rock belonging to the upper part of the New Egypt Formation. Paleontologist E.D. Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
described the remains, naming the creature "Lælaps" ("storm wind", after the dog in Greek mythology
Laelaps (mythology)
Laelaps was a Greek mythological dog who never failed to catch what he was hunting. In one version of Laelaps' origin, he was a gift from Zeus to Europa. The hound was passed down to King Minos. Minos had been cursed by his wife; he ejaculated scorpions and spiders that would devour the genitals...
that never failed to catch what it was hunting). Lælaps became one of the first dinosaurs described from North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
(following Hadrosaurus
Hadrosaurus
Hadrosaurus is a valid genus of hadrosaurid dinosaur. In 1858, a skeleton of a dinosaur from this genus was the first dinosaur skeleton known from more than isolated teeth to be found in North America. In 1868, it became the first ever mounted dinosaur skeleton...
, Aublysodon
Aublysodon
Aublysodon is a name given to a large number of carnivorous dinosaur teeth of a certain form found in numerous late Cretaceous period geological formations...
and Trachodon
Trachodon
Trachodon is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-age Upper Cretaceous Judith River Formation of Montana, U.S.A...
). Subsequently, it was discovered that the name Lælaps had already been given to a genus of mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
, and Cope's lifelong rival O.C. Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
changed the name in 1877 to Dryptosaurus.
During the 19th century, numerous theropod species in North America were assigned to the genus Dryptosaurus (often as Lælaps or Laelaps), only to be reclassified. Only one potential second species is sometimes recognized today, D. macropus, known from a partial hind limb found in the Navesink Formation
Navesink Formation
The Navesink Formation is a 66 to 70 mya greensand glauconitic marl and sand geological formation in New Jersey. It is known for it its Cretaceous era fossil shell beds and dinosaur bones.-Description:...
(probably roughly equivalent to the New Eagle Formation in time). Joseph Leidy
Joseph Leidy
Joseph Leidy was an American paleontologist.Leidy was professor of anatomy at the University of Pennsylvania, and later was a professor of natural history at Swarthmore College. His book Extinct Fauna of Dakota and Nebraska contained many species not previously described and many previously...
originally referred the specimen to Coelosaurus. Cope later recognized it as a distinct species, referring to it as Lælaps macropus, differing from the specimen now known as Dryptosaurus by its longer toes. Subsequently, most scientists had concluded that it probably belonged to Coelosaurus after all, but in 2004 paleontologist Thomas R. Holtz listed it as an indeterminate tyrannosauroid, possibly referable to the genus Dryptosaurus.
Classification
Dryptosaurus was the only large carnivore known in eastern North America before the discovery of AppalachiosaurusAppalachiosaurus
Appalachiosaurus is a genus of tyrannosauroid theropod dinosaur from the Late Cretaceous Period of eastern North America. Like almost all theropods, it was a bipedal predator. Only a juvenile skeleton has been found, representing an animal over 7 meters long and weighing over...
in 2005. During that time Dryptosaurus was classified in a number of theropod families. Originally considered a megalosaurid by Cope, it was later assigned to its own family (Dryptosauridae) by Marsh, and later found (through phylogenetic studies of the 1990s) to be a coelurosaur
Coelurosauria
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. In the past, it was used to refer to all small theropods, although this classification has been abolished...
, though its exact placement within that group remained uncertain. The discovery of the closely related (and more complete) Appalachiosaurus made it clear that Dryptosaurus was a primitive tyrannosauroid
Tyrannosauroidea
Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period...
.
The fossil material assigned to Dryptosaurus was reviewed by Ken Carpenter
Kenneth Carpenter
Kenneth Carpenter is a paleontologist. He is the museum director of the USU Eastern Prehistoric Museum and author or co-author of a number of books on dinosaurs and Mesozoic life...
in 1997 in light of the many different theropods discovered since Cope's day. He felt that due to some unusual features it couldn't be placed in any existing family and warranted placement in its own family, Dryptosauridae.
Dubious species
Numerous species have been assigned to Dryptosaurus based on very fragmentary material, and probably belong to various other types of theropod. These include:- D. macropus (Cope, 1868)
[originally Laelaps] - D. falculus (Cope, 1876)
[originally Laelaps] - D. hazenianus (Cope, 1876)
[originally Laelaps]
Another dubious species was Laelaps trihedrodon by Cope in 1877. Although the type specimen included a partial dentary, all material—except for a collection of five damaged partial tooth crowns (AMNH 5780)—has been lost. AMNH 5780 has many features in common with Allosaurus and is probably referable to that genus. However some of the Allosaurus-like characters of the tooth are primitive to theropods as a whole and may have been present in the less-studied or poorly preserved [Morrison Formation theropod species. Consequently the synonymization of L. trihedrodon with Allosaurus is tentative, despite its high likelihood.
Paleoecology
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
s are known from the same time and place as Dryptosaurus, the island continent of Appalachia
Appalachia (Mesozoic)
In the Mesozoic Era, Appalachia was a land area which is now an eastern part of the USA and Canada, separated from Laramidia by the Western Interior Seaway, which shrank, divided across the Dakotas, retreated south towards the Gulf of Mexico and finally dried up.-Fauna:From the Turonian age of the...
, and they may have been a prominent part of its diet. Nodosaurs were also present, although less likely to be hunted due to their armor plating.