Dryptosaurus (/ˌdrɪptoʊˈsɔːrəs/ DRIP-toh-SOR-əs) is a genus of eutyrannosaurian theropod dinosaur that lived on the island continent of Appalachia approximately 67-66 million years ago during the end of the Maastrichtian age of the Late Cretaceous period.

Although it is now largely unknown outside of academic circles, the famous 1897 painting of the genus by Charles R. Knight made Dryptosaurus one of the more widely known dinosaurs of its time, in spite of its poor fossil record.

First described by Edward Drinker Cope in 1866 and later renamed by Othniel Charles Marsh in 1877, Dryptosaurus is among the first theropod dinosaurs ever known to science.

In August 1866, paleontologist Edward Drinker Cope was notified of the discovery and encouraged to visit the marl pit to obtain the specimen.

The skeleton was then deposited at the Academy of Natural Sciences in Philadelphia under the catalogue number ANSP 9995 and includes; skull and dentary fragments, teeth, caudal vertebrae, humeri, an incomplete manus, a partial pelvis, and nearly complete left hindlimb.

However, four chevrons, a sternum, and a scapula which are now lost were also noted by Cope in addition to several sacral vertebrae which are now referred to the protostegid Pneumatoarthrus.

[2] Cope presented his description of the specimen to the Academy on August 21, 1866, naming it a new genus and species of dinosaur, Laelaps aquilunguis.

[6] Brusatte et al. (2011) noted that well-preserved, historic casts of most of the type material from ANSP 9995 and AMNH FARB 2438 are housed in the collections of the Natural History Museum in London (NHM OR50100).

The casts show some detail that is no longer preserved on the original specimens, which have significantly degraded due to pyrite disease.

The discovery of this genus gave North American paleontologists the opportunity to observe an articulated, albeit incomplete, theropod skeleton.

Laelaps macropus was also coined by Cope for a partial leg found in the Navesink Formation that Joseph Leidy had referred earlier to the ornithomimid Coelosaurus, distinguishing it from Dryptosaurus by its longer toes.

[10] Earlier that year, Brownstein (2017) analyzed the material of Laelaps macropus and found that only the partial tibia could be definitely classified as that of a tyrannosauroid and that the distal metatarsal could have been from an ornithomimosaur.

[12] In February 2018, based on specimens described by Baird and Horner (1979), Brownstein tentatively classified the partial teeth (USNM 7199 and ANSP 15332) as D. sp.

[17] According to Brusatte et al. (2011), Dryptosaurus can be distinguished based on the following characteristics: the combination of a reduced humerus (humerus: femur ratio = 0.375) and a large hand (phalanx I-1:femur ratio = 0.200), the strong mediolateral expansion of the ischial tubercle, which is approximately 1.7 times as wide as the shaft immediately distally, the presence of an ovoid fossa on the medial surface of the femoral shaft immediately proximal to the medial condyle (which is demarcated anteriorly by the mesiodistal crest and demarcated medially by a novel crest) the presence of a proximomedially trending ridge on the anterior surface of the fibula immediately proximal to the iliofibularis tubercle, the lip on the lateral surface of the lateral condyle of the astragalus being prominent and overlapping the proximal surface of the calcaneum, and metatarsal IV being observed with a flat shaft proximally (resulting in a semiovoid cross section that is much wider mediolaterally than it is long anteroposteriorly).

Cope (1866), Leidy (1868), and Lydekker (1888) noted obvious similarities with the genus Megalosaurus, which was known at the time from remains discovered in southeastern England.

In 1946, Charles W. Gilmore was the first to observe that certain anatomical features may link Dryptosaurus with coeval Late Cretaceous tyrannosaurids, Albertosaurus, and Tyrannosaurus.

[26] Proceratosaurus bradleyi Kileskus aristotocus Guanlong wucaii Sinotyrannus kazuoensis Juratyrant langhami Stokesosaurus clevelandi Dilong paradoxus Eotyrannus lengi Bagaraatan ostromi Raptorex kriegsteini Dryptosaurus aquilunguis Alectrosaurus olseni Xiongguanlong baimoensis Appalachiosaurus montgomeriensis Alioramus altai Alioramus remotus Tyrannosauridae Brownstein (2021) found Dryptosaurus to be the sister taxon to "Cryptotyrannus", an informally named theropod from the Merchantville Formation of Delaware.

The 1897 watercolor painting by Charles R. Knight titled Leaping Laelaps may represent the earliest depiction of theropods as highly active and dynamic animals.