Apatosaurus is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, A. ajax, in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 1916. Apatosaurus lived about 152 to 151 million years ago (mya), during the late Kimmeridgian to early Tithonian age, and are now known from fossils in the Morrison Formation of modern-day Colorado, Oklahoma, New Mexico, Wyoming, and Utah in the United States. Apatosaurus had an average length of 21–23 m (69–75 ft), and an average mass of 16.4–22.4 t. A few specimens indicate a maximum length of 11–30% greater than average and a mass of approximately 33 t.
Allosaurus is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period. The name "Allosaurus" means "different lizard", alluding to its unique concave vertebrae. It is derived from the Greek words ἄλλος and σαῦρος. The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.
Stegosaurus is a genus of herbivorous, four-legged, armored dinosaur from the Late Jurassic, characterized by the distinctive kite-shaped upright plates along their backs and spikes on their tails. Fossils of the genus have been found in the western United States and in Portugal, where they are found in Kimmeridgian- to Tithonian-aged strata, dating to between 155 and 145 million years ago. Of the species that have been classified in the upper Morrison Formation of the western US, only three are universally recognized: S. stenops, S. ungulatus and S. sulcatus. The remains of over 80 individual animals of this genus have been found. Stegosaurus would have lived alongside dinosaurs such as Apatosaurus, Diplodocus, Camarasaurus and Allosaurus, the latter of which may have preyed on it.
Camarasaurus was a genus of quadrupedal, herbivorous dinosaurs and is the most common North American sauropod fossil. Its fossil remains have been found in the Morrison Formation, dating to the Late Jurassic epoch, between 155 and 145 million years ago.
Barosaurus was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Dakota. It is present in stratigraphic zones 2–5.
Champsosaurus is an extinct genus of crocodile-like choristodere reptile, known from the Late Cretaceous and early Paleogene periods of North America and Europe (Campanian–Paleocene). The name Champsosaurus is thought to come from champsai, (χαμψαι) said in an Ancient Greek source to be an Egyptian word for "crocodiles", and sauros, (σαύρος) Greek for "lizard". The morphology of Champsosaurus resembles that of gharials, with a long, elongated snout. It was native to freshwater environments where it likely preyed on fish, similar to living gharials.
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont. Fossils have been found in the western United States and were first discovered in the late 19th century. Valdosaurus canaliculatus and Dysalotosaurus lettowvorbecki were both formerly considered to represent species of Dryosaurus.
Edmontonia is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation, the unit of rock where it was found.
Monoclonius is an extinct genus of herbivorous ceratopsian dinosaur found in the Late Cretaceous layers of the Judith River Formation in Montana, United States, and the uppermost rock layers of the Dinosaur Park Formation in Alberta, Canada dated to between 75 and 74.6 million years ago.
Dryptosaurus is a genus of basal eutyrannosaurian theropod dinosaur that lived on the island continent of Appalachia approximately 67.6 million years ago during the end of the Maastrichtian age of the Late Cretaceous period. Dryptosaurus was a large, bipedal, ground-dwelling carnivore that could grow up to 7.5 metres (25 ft) long and weigh up to 756–1,500 kilograms (1,667–3,307 lb). 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.
Epanterias is a dubious genus of theropod dinosaur from the Tithonian age Upper Jurassic upper Morrison Formation of Garden Park, Colorado. It was described by Edward Drinker Cope in 1878. The type species is Epanterias amplexus. This genus is based on what is now AMNH 5767, parts of three vertebrae, a coracoid, and a metatarsal. Although Cope thought it was a sauropod, it was later shown to be a theropod. Gregory S. Paul reassessed the material as pertaining to a large species of Allosaurus in 1988. Other authors have gone further and considered E. amplexus as simply a large individual of Allosaurus fragilis. In 2010, Gregory S. Paul and Kenneth Carpenter noted that the E. amplexus specimen comes from higher in the Morrison Formation than the type specimen of Allosaurus fragilis, and is therefore "probably a different taxon". They also considered its holotype specimen not diagnostic and classified it as a nomen dubium.
Thespesius is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota.
Dystrophaeus is an extinct genus of sauropod dinosaur. Its type and only species is Dystrophaeus viaemalae, named by Edward Drinker Cope in 1877. Its fossils were found in the Tidwell Member of the Morrison Formation of Utah. Due to the fragmentary condition of its only known specimen, the affinities of Dystrophaeus are uncertain, although excavations carried out at the discovery site since 1989 have uncovered more of the original specimen and hold the potential for an improved understanding of the taxon.
Camarasaurus supremus is a species of sauropod dinosaur that lived during the Jurassic period in what is now the western United States. It is the type species of Camarasaurus, which also includes the species Camarasaurus grandis, Camarasaurus lentus, and Camarasaurus lewisi. C. supremus was discovered by the paleontologist Edward Drinker Cope in 1877, at the outset of the Bone Wars, a period of scientific competition between Cope and his rival Othniel Marsh. C. supremus is the largest and geologically youngest species in its genus, and was contemporary with several other exceptionally large dinosaurs, such as Saurophaganax and Maraapunisaurus. Despite being the first discovered species of Camarasaurus, C. supremus is relatively rare and poorly known.
Edmontosaurus annectens, often colloquially and historically known as Anatosaurus, is a species of flat-headed saurolophine hadrosaurid dinosaur from the late Maastrichtian age at the very end of the Cretaceous period, in what is now western North America. Remains of E. annectens have been preserved in the Frenchman, Hell Creek, and Lance Formations. All of these formations are dated to the late Maastrichtian age of the Late Cretaceous period, which represents the last three million years before the extinction of the non-avian dinosaurs. E. annectens is also found in the Laramie Formation, and magnetostratigraphy suggests an age of 69–68 Ma for the Laramie Formation. Edmontosaurus annectens is known from numerous specimens, including at least twenty partial-to-complete skulls, discovered in the U.S. states of Montana, South Dakota, North Dakota, Wyoming, and Colorado, as well as the Canadian province of Saskatchewan. It had an extremely long and low skull, and was quite a large animal, growing up to approximately 12 metres (39 ft) in length and 5.6 metric tons in average asymptotic body mass, although it could have been even larger. E. annectens exhibits one of the most striking examples of the "duckbill" snout that is common to hadrosaurs. It has a long taxonomic history, and specimens have at times been classified as Diclonius, Trachodon, Hadrosaurus, Claosaurus, Thespesius, Anatosaurus, and Anatotitan before all being grouped together in Edmontosaurus.
Hypsirhophus is a genus of stegosaurian dinosaurs. It contains a single species, Hypsirhophus discurus, which is known only from a fragmentary specimen. The fossil consists of partial vertebrae from the back, three from the tail, and a piece of rib.
Apatosaurinae is a subfamily of diplodocid sauropods, an extinct group of large, quadrupedal dinosaurs, the other subfamily in Diplodocidae being Diplodocinae. Apatosaurines are distinguished by their more robust, stocky builds and shorter necks proportionally to the rest of their bodies. Several fairly complete specimens are known, giving a comprehensive view of apatosaurine anatomy.
Amphicoelias is a genus of herbivorous sauropod dinosaur that lived approximately 150 million years ago during the Tithonian of what is now Colorado, United States. Amphicoelias was moderately sized at about 18 metres (59 ft) in length and 15 metric tons in body mass, shorter than its close relative Diplodocus. Its hindlimbs were very long and thin, and its forelimbs were proportionally longer than in relatives.
Diplodocus is an extinct genus of diplodocid sauropod dinosaurs known from the Late Jurassic of North America. The first fossils of Diplodocus were discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a Neo-Latin term derived from Greek διπλός (diplos) "double" and δοκός (dokos) "beam", in reference to the double-beamed chevron bones located in the underside of the tail, which were then considered unique.
Galeamopus is a genus of herbivorous diplodocid sauropod dinosaurs. It contains two known species: Galeamopus hayi, known from the Late Jurassic lower Morrison Formation of Wyoming, United States, and Galeamopus pabsti, known from the Late Jurassic fossils from Wyoming and Colorado. The type species is known from one of the most well preserved diplodocid fossils, a nearly complete skeleton with associated skull.
