Archelon is an extinct marine turtle from the Late Cretaceous, and is the largest turtle ever to have been documented, with the biggest specimen measuring 460 cm (15 ft) from head to tail, 400 cm (13 ft) from flipper to flipper, and 2,200 kg (4,900 lb) in weight. It is known only from the Dakota Pierre Shale and has one species, A. ischyros. In the past, the genus also contained A. marshii and A. copei, though these have been reassigned to Protostega and Microstega, respectively. The genus was named in 1895 by American paleontologist George Reber Wieland based on a skeleton from South Dakota, who placed it into the extinct family Protostegidae. The leatherback sea turtle was once thought to be its closest living relative, but now, Protostegidae is thought to be a completely separate lineage from any living sea turtle.
Oliver Perry Hay was an American herpetologist, ichthyologist, and paleontologist.
Protostega is an extinct genus of sea turtle containing a single species, Protostega gigas. Its fossil remains have been found in the Smoky Hill Chalk formation of western Kansas and time-equivalent beds of the Mooreville Chalk Formation of Alabama. Fossil specimens of this species were first collected in 1871, and named by Edward Drinker Cope in 1872. With a length of 3 metres (9.8 ft), it is the second-largest sea turtle that ever lived, second only to the giant Archelon, and the third-largest turtle of all time behind Archelon and Stupendemys.
Protostegidae is a family of extinct marine turtles that lived during the Cretaceous period. The family includes some of the largest sea turtles that ever existed. The largest, Archelon, had a head one metre (39 in) long. Like most sea turtles, they had flattened bodies and flippers for front appendages; protostegids had minimal shells like leatherback turtles of modern times.
Hesperotestudo is an extinct genus of tortoise that lived from the Miocene to the Pleistocene. Its remains are known from North America, Central America and Bermuda. Further specimens identifiable only to genus have been found in El Salvador.
Psephophorus is an extinct genus of sea turtle that lived from the Oligocene to the Pliocene. Its remains have been found in Europe, Africa, North America, and New Zealand. It was first named by Hermann von Meyer in 1847, and contains seven species, P. polygonus, P. calvertensis, P. eocaenus, P. oregonesis, P. californiensis, P. rupeliensis, P. scaldii, and a species discovered in 1995, P. terrypratchetti.
Ctenochelys is an extinct genus of marine turtle, which existed during the Cretaceous period, and lived in the shallow waters of the Western Interior Seaway. Its fossils have been found in the Ripley Formation and Mooreville Chalk of central Alabama, United States. It was first named by C.H. Sternberg in 1904, and contains two species, C. stenoporus and C. acris.
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.
Euclastes is an extinct genus of sea turtles that survived the Cretaceous–Paleogene mass extinction. The genus was first named by Edward Drinker Cope in 1867, and contains three species. E. hutchisoni, was named in 2003 but has since been reassigned to the genus Pacifichelys, while E. coahuilaensis named in 2009 was reassigned as Mexichelys coahuilaensis in 2010.
Glyptops is an extinct genus of cryptodire turtle dating from the Late Jurassic and Early Cretaceous periods 155 to 99 m.y.a. Fossils have been found in South Dakota, Wyoming, Colorado, Utah, New Mexico, Oklahoma, and Texas from both the Morrison and Cedar Mountain formations. The type species is G. plicatulus, which had been named Compsemys plicatulus by Edward Drinker Cope.
Syllomus is an extinct genus of sea turtle from the Miocene-age deposits in the US Eastern Seaboard and Egypt.
The Smoky Hill Chalk Member of the Niobrara Chalk formation is a Cretaceous conservation Lagerstätte, or fossil rich geological formation, known primarily for its exceptionally well-preserved marine reptiles. Named for the Smoky Hill River, the Smoky Hill Chalk Member is the uppermost of the two structural units of the Niobrara Chalk. It is underlain by the Fort Hays Limestone Member; and the Pierre Shale overlies the Smoky Hill Chalk. The Smoky Hill Chalk outcrops in parts of northwest Kansas, its most famous localities for fossils, and in southeastern Nebraska. Large well-known fossils excavated from the Smoky Hill Chalk include marine reptiles such as plesiosaurs, large bony fish such as Xiphactinus, mosasaurs, flying reptiles or pterosaurs, flightless marine birds such as Hesperornis, and turtles. Many of the most well-known specimens of the marine reptiles were collected by dinosaur hunter Charles H. Sternberg and his son George. The son collected a unique fossil of the giant bony fish Xiphactinus audax with the skeleton of another bony fish, Gillicus arcuatus inside the larger one. Another excellent skeleton of Xiphactinus audax was collected by Edward Drinker Cope during the late nineteenth century heyday of American paleontology and its Bone Wars.
Pleurosternon is an extinct genus of cryptodire turtle from the late Jurassic period to the early Cretaceous period. Its type species, P. bullocki was described by the paleontologist Richard Owen in 1853. Since then, and throughout the late 19th century, many fossil turtles were incorrectly assigned to this genus.
Pancheloniidae is a clade of sea turtles It is defined as all turtles more closely related to cheloniid sea turtles than to dermochelyid ("leatherback") sea turtles.
The Ashley Formation is a geologic formation in South Carolina. It preserves fossils dating back to the Paleogene period.
The Washakie Formation is a geologic formation in northern Colorado and southern Wyoming. It preserves many mammal, bird, reptile and other fossils dating back to the Lutetian stage of the Eocene within the Paleogene period. The sediments fall in the Bridgerian and Uintan stages of the NALMA classification.
The Bridger Formation is a geologic formation in southwestern Wyoming. It preserves fossils dating back to the Ypresian Epoch of the Paleogene Period. The formation was named by American geologist Ferdinand Vandeveer Hayden for Fort Bridger, which had itself been named for mountain man Jim Bridger. The Bridger Wilderness covers much of the Bridger Formation's area.
Pantestudines is the group of all tetrapods more closely related to turtles than to any other animals. It includes both modern turtles (Testudines) and all of their extinct relatives.
Chelonides is a genus of late Jurassic turtle from marine deposits in Lower Saxony, Germany.
Naomichelys is an extinct genus of stem turtle known from the Early Cretaceous of the western US.
