Dryptosaurus

Dryptosaurus

Animalia

Dryptosaurus
Temporal range: Late Cretaceous, 67 Ma
Illustrated fossil remains
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Superfamily: Tyrannosauroidea
Family: Dryptosauridae
Marsh, 1890
Genus: Dryptosaurus
Marsh, 1877
Species: D. aquilunguis
Binomial name
Dryptosaurus aquilunguis
(Cope, 1866 [originally Laelaps])
Synonyms

Laelaps aquilunguis Cope, 1866 (preoccupied)
Megalosaurus aquilunguis (Cope, 1866)

Dryptosaurus (from Greek δρυπτο drypto, "tear" and σαυρος sauros, "lizard" ) 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".

Contents

Description

Estimated size, compared to human.

Dryptosaurus is estimated to have been 7.5 metres (25 ft) long and to have weighed 1.5 metric tons (1.7 short tons), although this is based on partial remains of one individual.[1] Like its relative Eotyrannus, 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.[2] These claws lend a meaning for the type species aquilunguis: eagle-clawed.

Discovery and species

Diagram showing the remains after Dryptosaurus.
An early painting by Charles R. Knight

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.[2] 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).[3] 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.[4]

Classification

Dryptosaurus was the only large carnivore known in eastern North America before the discovery of Appalachiosaurus in 2005.[5] 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.[6]

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.[7]

Paleoecology

An outdated historical depiction of Dryptosaurus confronting Elasmosaurus, with two Hadrosaurus in the background. By Cope, 1869.

Although certainly a carnivore, the paucity of known Cretaceous East Coast dinosaurs make ascertaining the specific diet of Dryptosaurus difficult.[2] Hadrosaurids 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.[2]

Impact on Popular Culture

Currently efforts are underway by Gary Vecchiarelli of Project: Dryptosaurus to get a mount of the skeleton established in a more permanent location hosted in New Jersey State Museum in Trenton. Project Dryptosaurus was established as a non-profit organization dedicated to educating the public and scientific community about the world’s forgotten second dinosaur skeleton from New Jersey, and thus resurrecting this specimen to its rightful position in the chronology of dinosaur discoveries. The Project’s backers and supporters include respected professionals in the paleo-community. The Project has been featured in Prehistoric Times magazine in Issue #94 and Weird New Jersey in Issue #34. Project Dryptosaurus overall is dedicated to advancing the science of dinosaur paleontology as well and is currently working on non-profit status as indicated on the website. [8]

References

  1. ^ Paul, G.S. (2010). The Princeton Field Guide to Dinosaurs, Princeton University Press, p. 100.
  2. ^ a b c d "Dryptosaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. p. 112-113. ISBN 978-0-7853-0443-2.
  3. ^ Cope, E.D. (1866). "Discovery of a gigantic dinosaur in the Cretaceous of New Jersey." Proceedings of the Academy of Natural Sciences of Philadelphia, 18: 275-279.
  4. ^ Holtz, T.R. (2004). "Tyrannosauroidea." Pp. 111-136 in Weishampel, Dodson and Osmolska (eds). The Dinosauria (second edition). University of California Press, Berkeley.
  5. ^ Carra, T.D., Williamson, T.E., and Schwimmer, D.R. (2005). "A new genus and species of tyrannosauroid from the Late Cretaceous (middle Campanian) Demopolis Formation of Alabama". Journal of Vertebrate Paleontology 25 (1): 119–143. doi:10.1671/0272-4634(2005)025[0119:ANGASO]2.0.CO;2. 
  6. ^ Carpenter, Ken & Russell, Dale A, Donald Baird, and R. Denton (1997). "Redescription of the holotype of Dryptosaurus aquilunguis (Dinosauria: Theropoda) from the Upper Cretaceous of New Jersey". Journal of Vertebrate Paleontology 17 (3): 561–573. doi:10.1080/02724634.1997.10011003. Archived from the original on 2007-03-10. http://web.archive.org/web/20070310231340/http://www.vertpaleo.org/jvp/17-561-573.html. 
  7. ^ Chure, Daniel J. (2001). "On the type and referred material of Laelaps trihedrodon Cope 1877 (Dinosauria: Theropoda)". In Tanke, Darren; and Carpenter, Kenneth (eds.). Mesozoic Vertebrate Life. Bloomington and Indianapolis: Indiana University Press. pp. 10–18. ISBN 978-0-253-33907-2. 
  8. ^ ERVOLINO, BILL (APRIL 13, 2010). "This dinosaur had a Jersey attitude". THE RECORD. http://www.northjersey.com/recreation/90722004_This_dinosaur_had_a_Jersey_attitude.html?page=all. Retrieved 23 June 2011. 
  • Carr and Williamson (2002). "Evolution of basal Tyrannosauroidea from North America". Journal of Vertebrate Paleontology 22 (3): 41A. 
  • [1] - Cretaceous Dinosaurs of the Southeastern United States by David T. King Jr.

External links

Tyrannoskull.jpg Dinosaurs portal

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