Antediluvian Beasts of the East: Dryptosaurus aquilunguis

Summer is the season which gives life to the animals of Cretaceous New Jersey. As the trees rustle in the cool breeze, a large bull Hadrosaurus minor grumbles to attract mates. His calls can be heard for miles, and can attract unwanted attention, including rival males. Hadrosaurus minor males frequently fight, sometimes killing one another in the heat of battle. Luckily for this male, only females appear from the forest, made interested by the hadrosaur’s distinctive bellows. The females will graze in close proximity to the male until they are ready to mate. However, this time of plenty will soon end, giving way to the cold, wet months of winter.

The vast expanses of the New Egypt wilderness host more then just dinosaurs. Crocodilians and marine reptiles frequent the area during the warm summer, feasting on the schools of fish which shoot up the deltaic plains of the coastal lowlands. Among them is the 14 foot long Thoracosaurus, a long-snouted crocodilian specializing in fish-hunting. These slender predators follow the large schools of Enchodus fish up and down the eastern shoreline of Appalachia. In winter, the cold-blooded thoracosaurs will leave the deltas of the Navesink for warmer hunting sites elsewhere. Other predators of the deltas, such as the mosasaur Halisaurus, will eek out a living a few miles off the coast of Appalachia, where they will be exposed to larger predators.

For other animals of the New Egypt wilderness, the coming winter months pose more of a threat. Many of the large herbivorous dinosaurs of the region will be forced into the nearby Appalachian mountains, which in the west eclipse their summer home of plenty. To reach the plateau within the mountains, the large herbivores of the region must embark on a long trek across 50 or more miles of treacherous terrain, and many will not survive.

Fall, and the calls of another large animal fill the New Egypt wilderness. Lambeosaurines, some 26 feet in length, are forming gigantic migrating herds. Males of this dinosaur are adorned will colorful head crests which they use to deter rivals and predators. The already forming heavy proto-feather coats of these hadrosaurs signal the coming of winter. They must store up fat to survive to cold, or else they will never see spring. Juveniles are especially at risk, and often will not even survive the first days of the trek up the mountains.

For another type of animal, the coming of winter is an advantage. The top predators of the region have been busy all summer raising the next generation, but now they stir from their nests. The most common species here is Dryptosaurus aquilunguis. Packs of these killers will torment the herds of herbivorous dinosaurs making their way through mountain passes. Unlike the hadrosaurs, whose bristly and somewhat sparse coats provide only a little protection from the cold, Dryptosaurus aquilunguis sport a coat of feathers similar in structure to the downy feathers of birds. Their warm coat provides a huge advantage when cold weather sets in, allowing them to thrive in the cold winter. Their padded feet, armed at the tip with large claws, give them ample traction during their climb up the sometimes rocky faces of the Appalachian mountains.

Winter finally shows its ugly head to the animals of the Appalachian wilderness. Although there will be little or no snow, long-lasting storms will drench the deltas with ice-cold water and temperatures will drop to an average of 2 degrees Celsius. The small animals of the deltas, like salamanders and frogs, will cling on to life here as best they can, but the large animals will now have to leave. The hadrosaurs start to march up the mountains, and are followed by the hungry Dryptosaurus aquilunguis, which seek to prey on the duck-billed dinosaurs. These predators hunt and kill dozens of hadrosaurs during the start of winter, feasting on the remains of the weary herbivores. Winter, however, will even test the might of the dryptosaurs, as the worst is yet to come.

Mid-December, and the battalions of migrating dinosaurs find themselves among the cold forests of the plateau they’ve set on out for. Even in these forests, insulated by mountains all around them, the height of winter is desolate, and sleet, hail, and rain are common sights. For the groups of dryptosaurs, these are the days which put them to the test. Among the trees, a mating pair cuddles for warmth. The hadrosaurs are faring even worse then their predators, and many browse among the bodies of their brethren which have succumbed to the cold. The hadrosaurs would fare even worse back in the coastal lowlands, where the constant cold weather kills the plants of the deltas. The pine trees here barely sustain these majestic titans, which, in turn, allow the dryptosaurs to survive.

As the hadrosaurs browse, the mating pair of dryptosaurs find a native resident of these alpine woodlands. A nodosaur, decked in armor from nose to tail, rips bark off the sleet-covered conifers as the theropods watch from behind a grove of dead magnolia trees. The female dryptosaur cautiously approaches the armored herbivore, which grunts to deter her. Taking notice, the dryptosaur backs off, deciding not to mess with an unknown herbivore. The Dryptosaurus aquilunguis will have to settle for hadrosaur meat.

Late January, and signs of spring bring hope to the weary dinosaurs. The dryptosaur pair has survived, and have been tracking a small group of ornithomimosaurs for a few days. They finally strike, killing a large ornithomimosaur using their immense hand claws. These weapons are only found on dryptosaurs, giving them another advantage over the other lineages of large predator that live in the Navesink ecosystem. These theropods have braved the harsh Appalachian winter, and are rewarded by warmer weather.

This same rise in temperature signals the herds of hadrosaurs to migrate back to the lowlands, where they will be joined by groups of leptoceratopsids which have migrated back to their summer home from the south. The hadrosaurs seem joyful as they march through the same mountain passes they faced months earlier.

As the herds of dinosaurs march back, the fading winter lashes out once more. A sudden downpour of sleet and snow rivets the migrating animals, who have already lost some of their winter coats. The storm has come from the cold, high peaks of the northern Appalachians, where winter always lurks. The hadrosaurs, however, will survive, due to the pounds of conifer matter they ingested while staying in the high plateau. The dryptosaur pair escape the storm undaunted, feeding on the carcass of a dead pterosaur which fell from the skies during one of the harsh storms of mid-winter.

The hadrosaurs have finally reached the promised land. They have braved the harsh wintry months, and feast on the warm, succulent plants of the deltas. For the dryptosaur pair, the end of winter gives way to another event. The spring is the mating season of the dryptosaurs, and the female Dryptosaurus aquilunguis of the pair will soon lay a clutch of eggs. By the middle of summer, the dryptosaur pair will welcome chicks. When again the onset of fall signals the migration of the hadrosaurs, these chicks, alongside their parents, will face the sleet storms of deep winter, and, if they survive, will join their parents in being the most versatile predators of the Cretaceous.

Dryptosaurus aquilunguis remains one of the most important dinosaurs in the history of paleontology. The remains of this large predator, discovered during the late 1800s, would set the foundation for the concept that dinosaurs were extremely active, adaptable animals, contrasting with the view of them as lumbering “evolutionary failures”. To completely understand the role Dryptosaurus aquilunguis played in what would eventually be known as the Dinosaur Renaissance, we must first venture to the time when the D. aquilunguis type specimen was discovered and uncovered from a marl deposit in Barnsboro, New Jersey.

It’s the late 1800s, and the partial skeleton of a predatory dinosaur is removed from New Jersey sediment. The excavation is under the watch of Edward Drinker Cope, a young paleontologist and comparative anatomist living in Haddonfield, NJ (Gallagher, 1997).  Incredibly, the theropod specimen is more well-preserved than any other found before it, provoking much excitement among Edward Cope and his team. Cope envisioned this new killer as an active hunter, running and leaping across the ancient New Jersey environment. Cope named the animal Laelaps aquilunguis, the “eagle-clawed catcher of all its quarry”, alluding to the dog Laelaps, which, in Greek mythology, always caught whatever it pursued. The success of the discovery of Laelaps prompted Cope to continue his excavation and exploration of the animals of the New Jersey marl, and more fascinating discoveries followed.

Cope had won the lottery. He knew Laelaps was related to the European Megalosaurus (another predatory dinosaur only known from scrappy remains) and since the former was known from a specimen far more complete then the latter, Cope could continue his mentor’s (influential paleontologist Joseph Leidy) work in finding out what these ancient creatures actually looked like in life. Cope’s Laelaps started to make scientists wonder if dinosaurs were active animals rather then the slow moving-behemoths they had been thought to be previously. It turned out Cope was correct in thinking that dinosaurs were very active animals, and the legacy of his “leaping Laelaps lives on today.

All this excitement attracted another prominent young scientist by the name of Othniel Charles Marsh. Marsh and Cope had known each other previously, but now Marsh had a more devious agenda. Marsh wanted some of the New Jersey marl specimens for himself, and during his stay started to establish his own group of marl diggers (Gallagher, 1997). Marsh and his newly-found henchmen started to collect the best specimens from the marl, much to Cope’s suspicion. Marsh also took it upon himself to publicly humiliate Cope any chance he got to,with  one of the most famous incidents concerning the plesiosaur Elasmosaurus. Marsh even took away Cope’s prize animal: Laelaps. Pointing out that the genus name in question  was already given to an arthropod, Marsh re-described Cope’s pride and joy as Dryptosaurus aquilunguis, the “eagle-clawed tearing lizard” (Gallagher, 1997), a name which still stands today. Cope was devastated, and continued to use Laelaps in his papers to refer to carnivorous dinosaurs (Gallagher, 1997). In his later years, Cope  would work with the artist Charles Knight to create a restoration of two Dryptosaurus fighting each other, a piece of paleoart which still sets the standard for paleontological illustration. 

Although Cope’s Laelaps might not have lasted, his theories on the ecology of the dinosaur did. Future discoveries would paint a dynamic picture of dinosaurs as active animals, asserting that his vision of Dryptosaurus as an active animal was true. Today, Dryptosaurus and its relatives (tyrannosauroids) are known to be fast, powerful predators just as Cope had envisioned. However, today the remains of Dryptosaurus are little compared to the material we have of other dinosaurs, and so some deduction and guesswork is required to understand the species ecologically, anatomically, etc.

The holotype of Dryptosaurus aquilunguis was unearthed from the New Egypt Formation (Brusatte et. al., 2011), a Maastrichtian-age (~72-65 MYA) deposit in what would become New Jersey. The New Egypt Formation is especially important as it provides a glimpse into one of the last Mesozoic Appalachian ecosystems. In fact, just above the New Egypt lies the Hornerstown Formation, a deposit which records the faunal change from a latest Cretaceous ecosystem including animals such as Mosasaurus sp. to a Cenozoic ecosystem recovering from the K-T extinction event. However, the Hornerstown does not contain the diverse dinosaurian fauna present in the New Egypt. Within the latter formation, Dryptosaurus aquilunguis had access to a wide range of dinosaur prey, including Hadrosaurus minor, another unnamed “duck-billed” dinosaur genus, and lambeosaurine hadrosaurs. Furthermore, ornithomimosaurs of the taxon Coelosaurus antiquus were also present within the New Egypt ecosystem, providing another food source for the aptly-named “tearing lizard”.

Although many of the dinosaurs and other animals present in the ecosystem of Dryptosaurus aquilunguis were related to forms in western North America and Asia, the morphology of these Appalachian forms differed from their relatives which lived far away. This is likely due to the unique faunal interchange which had defined the fauna of Appalachia ever since its start during the Cenomanian. Before the breakup of the North American landmass during the Late Cretaceous, an almost homogenous fauna could be found across the continent. On the east coast, the presence of a dinosaurian fauna almost completely homogenous to that of the west (Deinonychus sp., Tenontosaurus sp. , titanosauriformes, nodosauridae, allosauroidea) is found within the Arundel Formation of Maryland (Weishampel, 2006). Surprisingly, the Arundel Formation also shows the beginnings of changes in the North American fauna. The remains of an indeterminate ornithomimosaur and more surprisingly a tooth assigned to an indeterminate neoceratopsian have also been unearthed (Weishampel, 2006).


Deinonychus, a likely component of both eastern and western North American dinosaurian fauna. Photo by the author, 2015.

Skip ahead a couple million years, and Cenomanian Appalachia bears a “chimaera fauna”: a mix between taxa belonging to groups which had lived across the continent before the breakup of Laramidia and Appalachia and taxa which had evolved on or migrated to Appalachia. The best record of this time on Appalachia comes from Texas, where the Cenomanian Woodbine Formation preserves the remains of both animals with relatives found in the Arundel (nodosauridae, allosauroidea, dromaeosauridae) (Main, 2013)(Lee, 1997), but also those which do not have close relatives within the earlier formation (Protohadros) (i. e. Main, 2013). However, Protohadros does seem to have close relatives in the west (Prieto-Marquez & Norell, 2010)(Wenhao & Godefroit, 2012), suggesting that faunal interchange between Laramidian and Appalachian animals did occur at least in one direction.

Travel to the Campanian, and Alabama preserves a dinosaurian fauna seemingly created by the mixing of endemic and foreign fauna. Here, a derived non-tyrannosaurid tyrannosauroid (Appalachiosaurus) and a close relatives of hadrosaurids (Lophorhothon) appear, albeit not in the same formation. Finally, the Maastrichtian and Campanian sediments of New Jersey, North and South Carolina, Delaware, and Missouri preserve a terrestrial fauna almost completely unique from one anywhere else on the globe. Giant primitive hadrosaurids (Hypsibema, Ornithotarsus, “Parrosaurus”) are found across the continent, along with oddly primitive hadrosauroids (Lophorhothon, ?Claosaurus), hadrosaurines, which varied greatly in size (Hadrosaurus foulkii, Hadrosaurus minor), and leptoceratopsids (Longrich, 2016). 


Hadrosaurus foulkii fossils displayed at the Philadelphia Academy of Natural Sciences, Drexel University. Photo from Wikipedia.

Along with these animals, which seemingly arose on Appalachia after the splitting of the North American continent, forms found on eastern North America during the Early Cretaceous days of the Arundel Formation are still found within the ecosystems of Appalachia. Ornithomimids and nodosaurs are present in New Jersey, the Carolinas, and Alabama. Dromaeosaurs are also present in Alabama and possibly the Carolinas and New Jersey. Finally, primitive tyrannosaurs (Dryptosaurus macropus, Dryptosaurus aquilunguis, Appalachiosaurus montgomeriensis), echoes from the Early Cretaceous when their kind were just starting to become large predators, are the big-game hunters of Appalachia. The presences of a distinct fauna on Appalachia is supported by Longrich (2016).

The distinct fauna of Appalachia might also explain the intriguing morphology of some of material we have of Dryptosaurus aquilunguis. The massive hands tipped with huge claws which the “tearing lizard” possessed point to the prospect of this Appalachian tyrannosauroid employing a different style of attack than that of its western counterparts. Brusatte et. al. (2011) pointed out that the forelimb morphology of D. aquilunguis was “unlike that of any other tyrannosauroids”. The 2011 study also concluded Dryptosaurus had lost some grasping ability in comparison with more basal tyrannosaurs. Furthermore, unlike the tyrannosaurids of the west which possessed large, robust skulls (i.e. Tyrannosaurus, Daspletosaurus), Dryptosaurus seems to have possessed a more delicately constructed skull and, also unlike western tyrannosaurs, ziphodont teeth (Brusatte et. al., 2011).

Clearly Dryptosaurus was employing a different hunting style than other large tyrant dinosaurs, and the reason for this was perhaps due to the different types of prey the tyrannosaurs of the east and west were hunting. These features are, however, similar to those found in allosauroids, which are sometimes thought of as hunters of large game such as sauropods and non-hadrosaur ornithopods. The hadrosaurs of the east coast can be thought of as analogous to these other herbivorous dinosaur groups as they did possess large size in many cases and also seem to have not possessed any obvious defensive features (spikes, horns, armor).


The skeleton of Tyrannosaurus rex, a tyrannosaurid tyrannosauroid showing the robust skull morphology and small arms associated with derived tyrannosaurs. Photo by the author, 2015.

Almost the exact opposite occurs in many groups of large herbivores in the west, where ceratopsids boasted a menagerie of different horns and frills, ankylosaurs were coated in a tough layer of bony scutes and plates, and pachycephalosaurs sported domed, spiky heads. The tyrannosaurids of the west lived in a land where the “plain” hadrosaurs were in well-armed company. Dryptosaurus seems to have lived in an ecosystem where large animals with obviously defensive features were less common (a leptoceratopsid is known from the Tar Heel Formation of the Carolinas (Longrich, 2016), and nodosaurid material from the Campanian and Maastrichtian New Jersey has also been recovered (Weishampel, 2006), and that’s pretty much it as far as Appalachian dinosaur with defensive capabilities go). Dryptosaurus likely would have hunted and killed hadrosaurs by slicing flesh with its teeth and large claws, thereby inducing blood loss.

Dryptosaurus aquilunguis remains one of the most astounding dinosaurs ever found. The incredible history of its collection combined with its peculiar anatomical features stand as a hallmark of paleontological discovery in eastern North America as well as in the rest of the word. The “tearing lizard” truly is an amazing dinosaur, a hallmark of the fantastic animal oddities which evolved on the forgotten continent of Appalachia.



Dryptosaurus aquilunguis rests within the coastal forest that will one day become the New Egypt Formation. Also pictured are the ornithomimosaur Coelosaurus antiquus, an unnamed lambeosaurine hadrosaur, a dromaeosaurid, and enantiornithine birds. Foliage includes Metasequoia sp. (Dawn Redwood), Liriodendron (Tulip Trees, leaves pictured), Picea sp. (Spruce Tree), rosaceae sp., and Humulus sp. Illustration by the author. Colored pencils on paper, 2016.

For more on the dinosaurs of Cretaceous Appalachia, see these articles:

Antediluvian Beasts of the East: Hypsibema crassicauda

Antediluvian Beasts of the East: Hypsibema missouriense

Antediluvian Beasts of the East: Ornithotarsus immanis

PaleoNews #18 (National Fossil Day 2015 Special Edition) 


  1. Gallagher WB. 1997. When Dinosaurs Roamed New Jersey. New Brunswick: Rutgers University Press. pp. 34-39.
  2. Brusatte SL, Benson RBJ, Norell MA. 2011. The Anatomy of Dryptosaurus aquilunguis (Dinosauria: Theropoda) and a Review of its Tyrannosauroid Affinities. American Museum Novitates 3717: 1-53.
  3. Weishampel DB. 2006. Another look at the dinosaurs of the East Coast of North America. In: Coletivo Arqueológico-Paleontológico Salense, eds: Actas III Jornadas Dinosaurios Entorno. Salas de los Infantes: Burgos. pp. 129-168.
  4. Main D. 2013. Appalachian Delta Plain Paleoecology of the Cretaceous Woodbine Formation at the Arlington Archosaur Site in North Texas. D. Phil. Dissertation: University of Texas.
  5. Lee Y. 1997. The Archosauria from the Woodbine Formation (Cenomanian) in Texas. Journal of Paleontology 71(6): 1147–1156.
  6. Prieto-Marquez A & Norell MA. 2010. Anatomy and Relationships of Gilmoreosaurus mongoliensis (Dinosauria: Hadrosauroidea) from the Late Cretaceous of Central Asia. American Museum Novitates 3694: 1–52.
  7. Wenhao W & Godefroit P. 2012. Anatomy and Relationships of Bolong yixianensis, an Early Cretaceous Iguanodontoid Dinosaur from Western Liaoning, China. In: Godefroit P, eds: Bernissart Dinosaurs and Early Cretaceous Terrestrial Ecosystems. Bloomington: Indiana University Press. pp. 293–333.
  8. Longrich NR. 2016. A ceratopsian dinosaur from the Late Cretaceous of eastern North America, and implications for dinosaur biogeography. Cretaceous Research 57: 199-207.



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