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.
Xiphactinus is an extinct genus of large predatory marine bony fish that lived during the Late Cretaceous. Species in the genus bore a superficial resemblance to a gargantuan, fanged tarpon.
Deinodon is a dubious tyrannosaurid dinosaur genus containing a single species, Deinodon horridus. D. horridus is known only from a set of teeth found in the Late Cretaceous Judith River Formation of Montana and named by paleontologist Joseph Leidy in 1856. These were the first tyrannosaurid remains to be described and had been collected by Ferdinand Vandeveer Hayden. The teeth of Deinodon were slightly heterodont, and the holotype of Aublysodon can probably be assigned to Deinodon.
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.
Omosaurus is a dubious genus of extinct crurotarsan reptile, possibly a phytosaur, from the Late Triassic (Carnian) of North Carolina. Only scant remains are known, which makes Omosaurus hard to classify. The type, and only species, Omosaurus perplexus, was named and described in 1856 by Joseph Leidy.
Thespesius is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota.
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.
Bothremydidae is an extinct family of side-necked turtles (Pleurodira) known from the Cretaceous and Cenozoic. They are closely related to Podocnemididae, and are amongst the most widely distributed pleurodire groups, with their fossils having been found in Africa, India, the Middle East, Europe, North America and South America. Bothremydids were aquatic turtles with a high morphological diversity, indicative of generalist, molluscivorous, and piscivorous diets. Unlike modern pleurodires, which are exclusively freshwater, bothremydids inhabited freshwater, marine and coastal settings. Their marine habits allowed bothremydids to disperse across oceanic barriers into Europe and North America during the early Late Cretaceous (Cenomanian). The youngest records of the group are indeterminate remains from Saudi Arabia and Oman, dating to the Miocene.
Ischyrhiza is an extinct genus of sclerorhynchoid ray from the Late Cretaceous and Early Paleogene.
Stylemys is the first fossil genus of dry land tortoise belonging to the order Testudines discovered in the United States. The genus lived in temperate to subtropical areas of North America, Europe, and Asia, based on fossil distribution. The genus was first described in 1851 by Joseph Leidy. The tortoise was common in the prehistoric Badlands, especially Nebraska and South Dakota. The species has also been found in the formations in and around Badlands National Park. Fossil fragments have also been found in the Palm Park Formation of New Mexico.
Capitosaurus is an extinct genus of temnospondyl amphibians whose remains have been found in Spitsbergen and Germany. Its skull was 30 cm long, with a total length over 122 cm. Several species have been assigned to the genus over the years, but only C. polaris is still valid today.
Orycteocetus is an extinct genus of sperm whale from the Miocene of the northern Atlantic Ocean.
Peritresius is an extinct genus of sea turtle from the Late Cretaceous deposits in the US Eastern Seaboard.
The New Oxford Formation is a mapped bedrock unit consisting primarily of sandstones, conglomerates, and shales. The New Oxford Formation was first described in Adams County, Pennsylvania in 1929, and over the following decade was mapped in adjacent York County, Pennsylvania and Frederick County, Maryland. It was described as "red shale and sandstone with beds of micaceous sandstone, arkose, and conglomerate." The majority of this early mapping was done by George Willis Stose, Anna Isabel Jonas, and Florence Bascom.
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
Pliogonodon is an extinct genus of crocodylomorph. The type species, P. priscus, was named by Joseph Leidy in 1856. The holotype, known as USNM 7448, is a worn and broken tooth found from Phoebus Landing on the Cape Fear River in North Carolina. Although the age of the strata in which the tooth was found was not recorded, it is thought to have come from Miocene-age beds. The holotype and another tooth found at the same location are all that is known from the genus. The genus is considered a nomen dubium because of the lack of diagnostic features possessed by the teeth, and has been suggested to be synonymous with the alligatoroid Deinosuchus. Although Carroll (1988) assigned the genus to the basal neosuchian family Goniopholididae, current consensus is that Pligonodon is a Deinosuchus specimen.
Compsemys is an extinct genus of prehistoric turtles from the Late Cretaceous and Paleocene of North America and possibly Europe. The type species C. victa, first described by Joseph Leidy from the Hell Creek Formation in Montana in 1856, and another probable species C. russelli, described in 2012, from Paleocene deposits in France. Its affinites have long been uncertain, but it has recently been considered to be the most basal member of Paracryptodira, despite the clade first appearing in the Late Jurassic, and is sometimes included in its own family, Compsemydidae. A revision in 2020 found Compsemydidae to be more expansive, also containing Riodevemys and Selenemys from the Late Jurassic of Europe, and Peltochelys from the Early Cretaceous of Europe.
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.
Baena is an extinct genus of baenid turtles.
Bothremys is an extinct genus of bothremydid pleurodiran turtle that was discovered near Gloucester, New Jersey. The genus consists of type species B. cooki, B. arabicus, B. kellyi, and B. maghrebiana.
