Trachodon is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-age Upper Cretaceous Judith River Formation of Montana, U.S. It is a historically important genus with a convoluted taxonomy that has been all but abandoned by modern dinosaur paleontologists.
Megalosaurus is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic period of southern England. Although fossils from other areas have been assigned to the genus, the only certain remains of Megalosaurus come from Oxfordshire and date to the late Middle Jurassic.
Elasmosaurus (;) is a genus of plesiosaur that lived in North America during the Campanian stage of the Late Cretaceous period, about 80.5 million years ago. The first specimen was discovered in 1867 near Fort Wallace, Kansas, US, and was sent to the American paleontologist Edward Drinker Cope, who named it E. platyurus in 1868. The generic name means "thin-plate reptile", and the specific name means "flat-tailed". Cope originally reconstructed the skeleton of Elasmosaurus with the skull at the end of the tail, an error which was made light of by the paleontologist Othniel Charles Marsh, and became part of their "Bone Wars" rivalry. Only one incomplete Elasmosaurus skeleton is definitely known, consisting of a fragmentary skull, the spine, and the pectoral and pelvic girdles, and a single species is recognized today; other species are now considered invalid or have been moved to other genera.
Deinosuchus is an extinct genus of alligatoroid crocodilian, related to modern alligators and caimans, that lived 82 to 73 million years ago (Ma), during the late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek deinos (δεινός), "terrible", and soukhos (σοῦχος), "crocodile". The first remains were discovered in North Carolina in the 1850s; the genus was named and described in 1909. Additional fragments were discovered in the 1940s and were later incorporated into an influential, though inaccurate, skull reconstruction at the American Museum of Natural History. Knowledge of Deinosuchus remains incomplete, but better cranial material found in recent years has expanded scientific understanding of this massive predator.
Phytosaurs are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. and are sometimes referred to as parasuchians. Phytosauria, Parasuchia, Parasuchidae, and Phytosauridae have often been considered equivalent groupings containing the same species. Some recent studies have offered a more nuanced approach, defining Parasuchidae and Phytosauridae as nested clades within Phytosauria as a whole. Phytosaurs were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodilians in size, appearance, and lifestyle, as an example of convergence or parallel evolution. The name "phytosaur" means "plant reptile", as the first fossils of phytosaurs were mistakenly thought to belong to plant eaters.
Aublysodon is a genus of carnivorous dinosaurs known only from the Judith River Formation in Montana, which has been dated to the late Campanian age of the late Cretaceous period. The only currently recognized species, Aublysodon mirandus, was named by paleontologist Joseph Leidy in 1868. It is sometimes considered dubious now, because the type specimen consists only of an isolated premaxillary (front) tooth. Although this specimen is now lost, similar teeth have been found in many US states, western Canada, and Asia. These teeth almost certainly belong to juvenile tyrannosaurine tyrannosaurids, but most have not been identified to species level. However, it is likely that the type tooth belongs to one of the species in the genus Daspletosaurus, which was present in contemporary formations, and which matches specific details of the original tooth. The synapomorphies alleged to distinguish the Aublysodontinae, especially lack of serrations on premaxillary teeth could have been caused by tooth wear in life, postmortem abrasion, or digestion. Most other "aublysodontine"-type teeth may be from ontogenetic stages or sexual morphs of other tyrannosaurids.
Dacentrurus, originally known as Omosaurus, is a genus of stegosaurian dinosaur from the Late Jurassic to Early Cretaceous of Europe. Its type species, Omosaurus armatus, was named in 1875, based on a skeleton found in a clay pit in the Kimmeridge Clay in Swindon, England. In 1902 the genus was renamed Dacentrurus because the name Omosaurus had already been used for a crocodylian. After 1875, half a dozen other species would be named but perhaps only Dacentrurus armatus is valid. Finds of this animal have been limited and much of its appearance is uncertain. It was a heavily built quadrupedal herbivore, adorned with plates and spikes, reaching 8–9 metres (26–30 ft) in length and 5 metric tons in body mass.
Belodon is a genus of phytosaur, a crocodile-like reptile that lived during the Triassic. Its fossils have been found in Europe and elsewhere. The type species, Belodon plieningeri, was named by prolific German paleontologist Christian Erich Hermann von Meyer in 1844.
Thespesius is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota.
Clepsysaurus is a dubious genus of extinct archosaur described by Isaac Lea in 1851 from remains discovered in the Carnian Passaic Formation of Lehigh County, Pennsylvania. Two species are known: C. pennsylvanicus and C. veatleianus. The holotype of C. pennsylvanicus, ANSP 9526, 9555-71, 9594-5, consists of teeth, ribs and vertebrae, while the holotype of C. veatleianus, AMNH 2331, consists of a single tooth, with AMNH 2330, a tooth, as a referred specimen. Other specimens of C. pennsylvanicus are known, including ANSP 15071 and AMNH 2337.
Astrodon is a genus of large herbivorous sauropod dinosaur, measuring 20 m (66 ft) in length, 9 m (30 ft) in height and 20 metric tons in body mass. It lived in what is now the eastern United States during the Early Cretaceous period, and fossils have been found in the Arundel Formation, which has been dated through palynomorphs to the Albian about 112 to 110 million years ago.
Palaeoscincus is a dubious genus of ankylosaurian dinosaur based on teeth from the mid-late Campanian-age Upper Cretaceous Judith River Formation of Montana. Like several other dinosaur genera named by Joseph Leidy, it is an historically important genus with a convoluted taxonomy that has been all but abandoned by modern dinosaur paleontologists. Because of its wide use in the early 20th century, it was somewhat well known to the general public, often through illustrations of an animal with the armor of Edmontonia and the tail club of an ankylosaurid.
Lametasaurus named for the Lameta Formation, Jabalpur, India, is the generic name given to a possibly chimeric dinosaur species.
Rutiodon is an extinct genus of mystriosuchine phytosaurs from the Late Triassic of the eastern United States. The type species of Rutiodon, Rutiodon carolinensis, encompasses a large number of skulls and assorted postcranial fossils discovered in the Cumnock Formation of North Carolina. Fossils referable to the species are also known from Pennsylvania, New Jersey, and Virginia. Rutiodon carolinensis is the most well-described species of phytosaur in eastern North America, though its validity as a natural taxon has been questioned. Some paleontologists also recognize a larger and more robust species, Rutiodon manhattanensis, which is known from teeth and postcranial fossils from New Jersey and Pennsylvania.
Phytosaurus is a dubious genus of extinct parasuchid phytosaur found in an outcrop of the Keuper in Germany. Phytosaurus was the first phytosaur to be described, being done so by Georg Friedrich von Jaeger in 1828. The type species is P. cylindricodon and a second species, P. cubicodon, is also known.
Hyposaurus is a genus of extinct marine dyrosaurid crocodyliform. Fossils have been found in Paleocene aged rocks of the Iullemmeden Basin in West Africa, Campanian–Maastrichtian Shendi Formation of Sudan and Maastrichtian through Danian strata in New Jersey, Alabama and South Carolina. Isolated teeth comparable to Hyposaurus have also been found in Thanetian strata of Virginia. It was related to Dyrosaurus. The priority of the species H. rogersii has been debated, however there is no sound basis for the recognition of more than one species from North America. The other North American species are therefore considered nomina vanum.
Orycteocetus is an extinct genus of sperm whale from the Miocene of the northern Atlantic Ocean.
Dictyocephalus is an extinct genus of prehistoric temnospondyls; the only species is Dictyocephalus elegans. This taxon was one of the first metoposaurids to be discovered in North America, being discovered by Ebeneezer Emmons and briefly described by Joseph Leidy in 1856 in the Newark supergroup exposures of Chatham County, North Carolina. At the time, Leidy was uncertain of much of the anatomy of D. elegans, which is represented only by a small partial skull and made only brief descriptions and measurements of a few elements, with an estimated size based on the long-snouted trematosaur Trematosaurus. Emmons provided the first figures of the specimen the following year. Romer (1947) briefly mentioned that the specimen was indistinguishable from "Buettneria" (Koskinonodon). The taxon was not revisited in much detail until the revision of the Metoposauridae by Ned Colbert and John Imbrie in 1956. These authors pointed out that many of the features listed by Leidy to be diagnostic for D. elegans were too generic to either make comparisons or to prove its specific affinities. Chowdhury (1965) did not formally place D. elegans within the Metoposauridae. Subsequent authors proposed that D. elegans might represent a juvenile of a specific taxon, but uncertainty resulted from interpretations of the absence an otic notch and a tabular horn, features seen in larger metoposaurids. Joseph Gregory suggested that it specifically represented a juvenile of Metoposaurus but indicated a preference to maintain the name in a form restricted to the holotype and to designate it as a nomen vanum. Beth Davidow-Henry re-appraised the holotype in light of new material of small metoposaurids. She pointed out that if the absence of otic notches was considered to be a defining feature, then D. elegans would probably be synonymous with Anaschisma from Wyoming, but refrained from formalizing this in the absence of information regarding changes to the otic notch during development. Dictyocephalus was thus maintained as a valid genus of metoposaurids with shallow otic notches. The most recent revision of the metoposaurids by Adrian Hunt stated that the holotype was too fragmentary to be diagnostic and designated D. elegans as a nomen dubium within Temnospondyli
Thecachampsa is an extinct genus of gavialoid crocodylian, traditionally regarded as a member of the subfamily Tomistominae. Fossils have been found from the eastern United States in deposits of Miocene age. Those named in the 19th century were distinguished primarily by the shape of their teeth, and have since been combined with T. antiquus. More recently erected species were reassigned from other genera, although their assignment to Thecachampsa has since been questioned.
Compsosaurus is an extinct genus of phytosaur, a crocodile-like reptile that lived during the Triassic. Its fossils have been found in North Carolina. The type species, Compsosaurus priscus, was named by American paleontologist Joseph Leidy in 1856, although other sources say 1857. Compsosaurus may have been the same animal as the related Belodon.
