Dryptosaurus

Dryptosaurus ( ; meaning "tearing lizard") 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. Like other tyrannosaurs, Dryptosaurus was a bipedal carnivore with a long tail and elongated skull. Unlike other tyrannosaurs like Tyrannosaurus and Tarbosaurus, Dryptosaurus possessed large forelimbs ending in large claws and lithe hindlimbs. Size estimates place it at in length and in mass. The genus had ziphodont (sharp, blade-like, laterally compressed) dentition, dissimilar to that of larger tyrannosaurs.…

Dryptosaurus ( ; meaning "tearing lizard") 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. Like other tyrannosaurs, Dryptosaurus was a bipedal carnivore with a long tail and elongated skull. Unlike other tyrannosaurs like Tyrannosaurus and Tarbosaurus, Dryptosaurus possessed large forelimbs ending in large claws and lithe hindlimbs. Size estimates place it at in length and in mass. The genus had ziphodont (sharp, blade-like, laterally compressed) dentition, dissimilar to that of larger tyrannosaurs. Dryptosaurus is a member of Eutyrannosauria, the clade including Tyrannosauridae and tyrannosaurs like Nanotyrannus and Bistahieversor but excluding more basal tyrannosaurs like Dilong. This puts Dryptosaurus in an intermediate position between lithe, early tyrannosaurs and the large tyrannosaurids. However, some studies have also put it in its own family, Dryptosauridae, or in Nanotyrannidae. Dryptosaurus is one of few Cretaceous dinosaurs known from the Eastern United States. During the Late Cretaceous, North America was divided into two continents; Appalachia and Laramidia. The breakup of North America into these continents spurred the evolution of unique characteristics in Appalachian tyrannosaurs not observed in Laramidian tyrannosaurs. Fossils of Dryptosaurus are known from the marine New Egypt Formation where dinosaur bodies floated out to sea and became fossilized. Mosasaurs, fish, sharks, and other marine fauna are represented in this formation. ==Discovery and species== Up until 1866, theropods from the United States were only known from isolated teeth discovered by Ferdinand Van Hayden during Geological Survey excursions into Montana. During the summer of 1866, workers from the West Jersey Marl Company uncovered an associated theropod skeleton in sediments coming from the New Egypt Formation in a quarry near Barnsboro, New Jersey. This formation dates to the Maastrichtian stage of the Late Cretaceous period and is part of the Monmouth Group. In August 1866, American paleontologist Edward Drinker Cope was notified of the discovery and encouraged to visit the marl pit to obtain the specimen. When he arrived, he was thoroughly surprised by the skeleton's completeness and uniqueness, calling it the "finest discovery I have yet made". 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 were also noted by Cope, however they have since been lost. Several sacral vertebrae Cope assigned to Dryptosaurus are now believed to belong to the protostegid turtle Pneumatoarthrus. An isolated metatarsal IV (AMNH FARB 2438) possibly belonging to ANSP 9995 was found at the same locale, but this has come into question. It was in Cope's possession and purchased by the American Museum of Natural History in 1902, however it was not mentioned by Cope until an 1870 paper. 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. Some of the bones have evidence of molding, which was possibly done by Benjamin Waterhouse Hawkins during his failed project to erect a Paleozoic Museum in Central Park, New York. of Dryptosaurus (center) confronting Elasmosaurus, with Mosasaurus, Osteopygis, Thoracosaurus and two Hadrosaurus in the background. Illustration for an article by Edward Drinker Cope in The American Naturalist, April 1869.]] On 21 August 1866, Cope presented his description of ANSP 9995 to the American Philosophical Society at what is now the Academy of Natural Sciences, naming it a new genus and species of dinosaur, Laelaps aquilunguis. "Laelaps", which is derived from the Greek word "hurricane" or "storm wind", was also the name of a dog in Greek mythology who never failed to catch what it was hunting. In the 1870s, conflict began between Cope and another American paleontologist, Othniel Charles Marsh, leading to the onset of the Bone Wars. In 1877, Marsh pointed out that Cope's genus name Laelaps was preoccupied by a genus of mite, leading to Marsh to erect the genus name Dryptosaurus. This name derives from the Greek δρύπτω drypto "tear" and σαῦρος sauros "lizard", creating "tearing reptile". Despite this, Cope continued to use the name Laelaps, refusing to use Dryptosaurus. The discovery of this genus gave North American paleontologists the opportunity to observe an articulated, albeit incomplete, theropod skeleton. During the late 19th century, this genus became a wastebasket taxon for the referral of isolated theropod elements from across North America, given that Tyrannosauroidea was not recognized as a distinct group of large theropods at the time and numerous theropod species were assigned to it (often as Lælaps or Laelaps), only to be later reclassified. ===Other species=== ==Description== Dryptosaurus is estimated to have been long and , although this is based on partial remains of one individual. Like its relative Eotyrannus, Dryptosaurus seems to have had relatively long arms when compared with more derived tyrannosaurs, such as Tyrannosaurus. Its hands, which are also relatively large, were once believed to have had three fingers. Brusatte et al. (2011), however, observed an overall similarity in the shape of the available phalanges of Dryptosaurus with those of derived tyrannosaurids and noted that Dryptosaurus may have had only two functional digits. Each of its fingers were tipped with an eight-inch long, talon-like claw. Its arm morphology suggests that arm reduction in tyrannosauroids may not have proceeded in a uniform fashion. Dryptosaurus may have used both its arms and its jaws as weapons when hunting, capturing, and processing its prey. claw bone|left]] The type specimen is a fragmentary skeleton belonging to a single adult individual, ANSP 9995. ANSP 9995 consists of a fragmentary right maxilla, a fragmentary right dentary, a fragmentary right surangular, lateral teeth, 11 middle-distal caudal vertebrae, both the left and right humeri, three manual phalanges from the left hand (I-1, II-2, and an ungual), the shafts of the left and right pubic bones, a fragmentary right ischium, the left femur, the left tibia, the left fibula, the left astragalus, and a midshaft fragment of metatarsal III. The ontological maturity of the holotype individual is supported by the fact that the neurocentral sutures are closed in all of its caudal vertebrae. AMNH FARB 2438 consists of left metatarsal IV, which are likely from the same individual as the holotype. The fragmentary right maxilla preserves the three alveoli in full and the fourth only partially. The authors were able to ascertain that Dryptosaurus had ziphodont dentition. The shape of the alveolus situated on the anterior portion of the fragment suggests that it housed a tooth that was smaller and more circular than the others. This incisiform tooth is common among tyrannosauroids. The disarticulated teeth recovered are transversely narrow, serrated (17–18 denticles/cm), and recurved. The femur is only 3% longer than the tibia. The longest manual ungual phalanx recovered measured in length. The morphology of the proximal portion of metatarsal IV suggests that Dryptosaurus had an arctometatarsalian foot, an advanced feature shared by derived tyrannosauroids, such as Albertosaurus and Tyrannosaurus, in which the third metatarsal is "pinched" between the second and fourth metatarsals. with scaly skin]] 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). ==Classification== Topology A: Maximum parsimony tree (K = 12) Topology B: BI-FBD tree ==Paleoecology== The lithe build and elongated pes of Dryptosaurus and the Merchantville taxon are more similar to those of earlier tyrannosauroids like Moros and Suskityrannus, however the size of Dryptosaurus is in line with those of Laramidian tyrannosauroids. This led Brownstein (2021) to note that megapredatory tyrannosauroids in Appalachia evolved lightly built peses and skulls not adapted for osteophagy (bone eating) in contrast to the robust arctometatarsalian peses and robust, osteophagus jaws of Laramidian tyrannosauroids. Additionally, Dryptosaurus shows a menagerie of unique features like a lightly framed skull, ziphodont teeth, and a large raptorial, manus that forms a unique body plan among tyrannosauroids. Despite this, Dryptosaurus and the Merchantville taxon occupied the same megapredatory niche as tyrannosaurids, a role previously filled in Appalachia by large allosauroids. In the Atlantic Coast Plain, Dryptosaurus and the Merchantville taxon likely preyed on hadrosaurids, ornithomimosaurs, and ankylosaurs, which are all represented by fragmentary remains. Cope theorized that Dryptosaurus predated upon Hadrosaurus as Megalosaurus preyed on Iguanodon in the Wealden and Oolite Groups of England and Aublysodon preyed on Trachodon in the "Nebraska Beds". However, Dryptosaurus and Hadrosaurus come from different fossil formations. during the Upper Cretaceous]] The New Egypt Formation where Dryptosaurus fossils are known was underwater during the Late Cretaceous period. The Dryptosaurus holotype was an individual that floated out to sea, sunk to the sea floor, and became fossilized. This area is thought to have been a deeper-water area of the Tinton and Red Bank Formations. Strata of the New Egypt Formation is composed of massive clayey, glauconitic marl that was later used in fertilizers. Mining of the glauconitic marls in the West Jersey Marl Company Pit for fertilizers led to the discovery of fossils like those of Dryptosaurus. The New Egypt Formation is part of the Monmouth Group and overlies the Navesink Formation, from which possible Dryptosaurus fossils have been reported. Dryptosaurus lived along two other dinosaurs in the New Egypt Formation, the dubious hadrosaurid Hadrosaurus minor and a potential lambeosaurine. Being a marine deposit, most of the fossils found in the formation come from aquatic life. Marine reptiles are represented by crocodylomorphs like Hyposaurus, turtles like Agomphus, Euclastes, and Pneumatoarthrus, and the mosasaurids Mosasaurus, Prognathodon, and an indeterminate russellosaurine. Chondricthian fish from the New Egypt Formation include the chimaera Edaphodon, the sharks, Cretalamna, Ginglymostoma, and Squalicorax, the rays Dasyatis and Rhombodus, the sawskates Sclerorhynchus, Ischyrhiza, and Ptychotrygon, and the guitarfish Rhinobatos. As for bony fish, the pycnodont Anomoeodus has been reported from the formation. Some invertebrates are also known from the site, such as the bivalve Cucullaea and the cephalopod Baculites. ==Leaping Laelaps== , 1897]] The 1897 watercolor painting by Charles R. Knight titled Leaping Laelaps may represent the earliest depiction of theropods as highly active and dynamic animals. Knight's restoration was guided by Edward Drinker Cope and Henry Fairfield Osborn, who believed that Laelaps (Dryptosaurus) was an agile animal. The original painting is now preserved in the AMNH collections. This active and lively depiction of dinosaurs was later echoed by the Dinosaur Renaissance in the 1970s. By contrast, most 19th-century illustrations of large carnivorous dinosaurs like Megalosaurus presented dinosaurs as large, slow, and tail-dragging. ==See also== Timeline of tyrannosaur research ==References== - Cretaceous Dinosaurs of the Southeastern United States by David T. King Jr. ==External links== [http://njfossils.net/meateating.html Dryptosaurus aquilunguis

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