The Western Interior Seaway was a large inland sea that split the continent of North America into two landmasses. The ancient sea, which existed from the early Late Cretaceous to the earliest Paleocene, connected the Gulf of Mexico, through the United States and Canada, to the Arctic Ocean. The two land masses it created were Laramidia to the west and Appalachia to the east. At its largest extent, it was 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long.
Microsauria is an extinct, possibly polyphyletic order of amphibians from the late Carboniferous and early Permian periods. It is the most diverse and species-rich group of lepospondyls. Recently, Microsauria has been considered paraphyletic, as several other non-microsaur lepospondyl groups such as Lysorophia seem to be nested in it. Microsauria is now commonly used as a collective term for the grade of lepospondyls that were originally classified as members of Microsauria.
Dolichorhynchops is an extinct genus of polycotylid plesiosaur from the Late Cretaceous of North America, containing three species, D. osborni, D. bonneri and D. tropicensis, as well as a questionably referred fourth species, D. herschelensis. Dolichorhynchops was an oceangoing prehistoric reptile. Its Greek generic name means "long-nosed face".
Alocolytoceras is a lytoceratid ammonite with whorls that pass during growth from round to oval, rounded-quadrate, or compressed; with about 19 deep constrictions per whorl, with as many as 21 sharp ribs in between. The shell is evolute. All whorls are visible from either side.
Aulacosphinctes is an extinct genus of ammonoid cephalopod that lived during the Late Jurassic and had a widespread distribution.
Brachauchenius is an extinct genus of pliosaurid that lived in North America and Morocco during the Late Cretaceous.
Styxosaurus is a genus of plesiosaur of the family Elasmosauridae. Styxosaurus lived during the Campanian age of the Cretaceous period. Two species are known: S. snowii and S. browni.
Newmarracarroceras is an ammonite from the early middle Jurassic with a ribbed subinvolute shell with a keel running along the venter, or outer rim. The umbilicus is moderately wide, exposing the inner whorls exposed in part.
The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico.
Toxochelys is an extinct genus of marine turtle from the Late Cretaceous period. It is the most commonly found fossilized turtle species in the Smoky Hill Chalk, in western Kansas.
Dakotasuchus is a genus of goniopholidid mesoeucrocodylian. Its fossils have been recovered from the Cenomanian-age Upper Cretaceous Dakota Sandstone of Kansas. The type specimen was found in an iron-cemented sandstone concretion near Salina. This concretion was broken into two large pieces; more of the specimen was probably present originally, but by the time it was found only the torso and short portions of the neck and tail remained. Twenty pairs of bony scutes ran down the midline of the back. The vertebrae lacked the procoelous articulation of more derived crocodyliforms. Dakotasuchus had short broad shoulder blades, suggesting it had stout powerful forelimbs and perhaps terrestrial habits. M. G. Mehl, who described the genus, estimated the length of the type individual when complete to have been 3–4 metres (9.8–13.1 ft). The type species is D. kingi, named for Professor King, a former dean of Kansas Wesleyan University. Mehl did not classify his new genus to a more inclusive group than Mesosuchia. Robert Carroll assigned Dakotasuchus to Goniopholididae in 1988. In 2017, fossils of Dakotasuchus kingi which consisted of a coracoid, scutes, a dorsal vertebrate and postcranial bones were found in Utah, specifically in the Cedar Mountain Formation's Mussentuchit Member.
Coroniceras is a genus in the Arietitidae, a family in the ammonitid superfamily Psiloceratoidea, from the lower Sinermurian stage in the Lower Jurassic. It is a sub zone ammonite of the Arnioceras semicostatum Zone.
The Carlile Shale is a Turonian age Upper/Late Cretaceous series shale geologic formation in the central-western United States, including in the Great Plains region of Colorado, Kansas, Nebraska, New Mexico, North Dakota, South Dakota, and Wyoming.
Coilopoceras is a compressed, involute, lenticular ammonitid from the Cretaceous, with a narrow venter and raggedy ammonitic suture; type of the Coilopoceratidae, a family in the Acanthoceratoidea of the suborder Ammonitina.
During most of the Late Cretaceous the eastern half of North America formed Appalachia, an island land mass separated from Laramidia to the west by the Western Interior Seaway. This seaway had split North America into two massive landmasses due to a multitude of factors such as tectonism and sea-level fluctuations for nearly 40 million years. The seaway eventually expanded, divided across the Dakotas, and by the end of the Cretaceous, it retreated towards the Gulf of Mexico and the Hudson Bay. This left the island masses joined in the continent of North America as the Rocky Mountains rose. From the Cenomanian to the end of the Campanian ages of the Late Cretaceous, Appalachia was separated from the rest of North America. As the Western Interior Seaway retreated in the Maastrichtian, Laramidia and Appalachia eventually connected. Because of this, its fauna was isolated, and developed very differently from the tyrannosaur, ceratopsian, hadrosaurid, pachycephalosaur and ankylosaurid dominated fauna of the western part of North America, known as "Laramidia".
Idoceras is a genus of perisphictacean ammonite, belonging to the Perisphinctidae subfamily Idoceratinae. The genus is known from the Upper Jurassic, with a widespread distribution. Shells of Idoceras are evolute, with a wide umbilicus; ribbing strong, bifurcate high on flanks. Suture simpler than in the similar Ataxioceras.
Paleontology in Oklahoma refers to paleontological research occurring within or conducted by people from the U.S. state of Oklahoma. Oklahoma has a rich fossil record spanning all three eras of the Phanerozoic Eon. Oklahoma is the best source of Pennsylvanian fossils in the United States due to having an exceptionally complete geologic record of the epoch. From the Cambrian to the Devonian, all of Oklahoma was covered by a sea that would come to be home to creatures like brachiopods, bryozoans, graptolites and trilobites. During the Carboniferous, an expanse of coastal deltaic swamps formed in areas of the state where early tetrapods would leave behind footprints that would later fossilize. The sea withdrew altogether during the Permian period. Oklahoma was home a variety of insects as well as early amphibians and reptiles. Oklahoma stayed dry for most of the Mesozoic. During the Late Triassic, carnivorous dinosaurs left behind footprints that would later fossilize. During the Cretaceous, however, the state was mostly covered by the Western Interior Seaway, which was home to huge ammonites and other marine invertebrates. During the Cenozoic, Oklahoma became home to creatures like bison, camels, creodonts, and horses. During the Ice Age, the state was home to mammoths and mastodons. Local Native Americans are known to have used fossils for medicinal purposes. The Jurassic dinosaur Saurophaganax maximus is the Oklahoma state fossil.
Lytoceras is an ammonite genus that was extant during most of the Jurassic and Cretaceous periods, and is the type genus for the family Lytoceratidae. These cephalopods were fast-moving nektonic carnivores.
The Valentine Formation is a geologic unit formation or member within the Ogallala unit in northcentral Nebraska near the South Dakota border. It preserves fossils dating to the Neogene period and is particularly noted for Canid fossils. A particular feature of the Valentine is lenticular beds of green-gray opaline sandstone that can be identified in other states, including South Dakota, Nebraska, Kansas, and Colorado. Even though three mammalian fauna stages can be mapped throughout the range of the Ogallala, no beddings of the Ogallala are mappable and all attempts of formally applying the Valentine to any mappable lithology beyond the type location have been abandoned. Even so, opaline sandstone has been used to refer to the green-gray opalized conglomerate sandstone that is a particular feature of the lower Ogallala.
The Fort Hays Limestone is a member of the Niobrara Formation of the Colorado Group exposed in Colorado, Kansas, Nebraska, and South Dakota and is named for the bluffs near the old Fort Hays, a well-known landmark in western Kansas.
