Open Paleo

Dryptosaurus

Marsh, 1877 DRIP-toh-SOR-uhs /ˌdrɪptoʊˈsɔːrəs/

From Greek drypto (to tear) + sauros (lizard): 'tearing lizard'.

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Dryptosaurus 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.

Diagnosis

  1. Great external trochanter of femur massive and elevated to plane of head, separated only by slight depression; femoral head not projecting far beyond shaft and without constriction below
  2. Third trochanter on femur small and positioned lower than in any known Dinosaur, less than one-third femur length from inner distal condyle
  3. Tibia with cuneiform distal articular surface (not lozenge-shaped); anterior ridge very strong and much incurved; shaft much compressed antero-posteriorly
  4. Ungueal phalanges remarkably large and strongly compressed, with eagle-like form; large flexor-tendon insertion process separated by groove extending to tip
  5. Humeri relatively short (less than half femur length), proximally much dilated with strong postero-external ala and shorter antero-internal dilatation

Species

Dryptosaurus aquilunguis (Cope, 1866)

Type species

First named as Laelaps aquilunguis

From Latin 'aquila' meaning 'eagle' and 'unguis' meaning 'claw' or 'nail', referring to the large, talon-like claws on the forelimbs.

Holotype
ANSP 9995 , Academy of Natural Sciences of Philadelphia
Material
Portions of lower jaw with teeth, scapular arch, possible clavicles, two humeri, left femur, right tibia and fibula, numerous phalanges, fragmentary lumbar, sacral, and caudal vertebrae
Horizon
New Egypt Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
West Jersey Marl Company's pits, New Jersey, United States

Synonyms of the genus

Name Type Reason
Laelaps preoccupied Name preoccupied by Laelaps (Acari).

References

  1. Baird, D.; Horner, J. R. (1979). Cretaceous dinosaurs of North Carolina. Brimleyana 2: 1-28. https://www.biodiversitylibrary.org/part/442233

    Gives the type, ANSP 9995, as from the "chocolate greensand bed" or New Egypt Formation.

    baird1979a
  2. 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.

    Original description, as Laelaps aquilunguis.

    cope1866a
  3. Marsh, O. C. (1877). Notice of a new and gigantic dinosaur, Titanosaurus. American Journal of Science s3-14(79): 87-88. American Journal of Science (AJS). doi:10.2475/ajs.s3-14.79.87

    Erects Dryptosaurus as a replacement name for the preoccupied Laelaps Cope, 1866.

    marsh1877b
  4. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c