Trilophosaurs are lizard-like Triassic allokotosaur reptiles related to the archosaurs. The best known genus is Trilophosaurus, a herbivore up to 2.5 metres long. It had a short, unusually heavily built skull, equipped with massive, broad flattened cheek teeth with sharp shearing surfaces for cutting up tough plant material. Teeth are absent from the premaxilla and front of the lower jaw, which in life were probably equipped with a horny beak.
Archaeoceti, or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene. Representing the earliest cetacean radiation, they include the initial amphibious stages in cetacean evolution, thus are the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti. This initial diversification occurred in the shallow waters that separated India and Asia 53 to 45 mya, resulting in some 30 species adapted to a fully oceanic life. Echolocation and filter-feeding evolved during a second radiation 36 to 35 mya.
Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous. Several species survived into the final stage of the Cretaceous, the Maastrichtian.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2000.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2002.
The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian, in which the connecting rings are thin and siphuncle segments are variably expanded. At present the order consists of some 16 families, a few of which, such as the Oncoceratidae, Brevicoceratidae, and Acleistoceratidae contain a fair number of genera each while others like the Trimeroceratidae and Archiacoceratidae are represented by only two or three.
Cadomites is an extinct ammonite genus from the superfamily Stephanoceratoidea that lived during the Middle Jurassic.
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.
Lissoceras is an involute, smooth or finely vetrolaterally ribbed, ammonite with a blunt, un-keeled venter, included in the Haploceratidae, that lived from the Lower Bajocian - Middle Oxfordian in what is now Europe, south Asia, and southern Alaska.
Graphoceras is an extinct ammonite genus included in the hildoceratacean family Graphoceratidae that lived during the Aalenian and Bajocian stages, Middle Jurassic in what is now Europe, north Africa, and Iran.
Ptychoceratodus is an extinct genus of lungfish living from Early Triassic to Middle Jurassic. It was established by Otto Jaekel for one species, transferred from Ceratodus genus. Type species is P. serratus from the Middle Triassic of Switzerland and Germany. Ptychoceratodus had two pairs of massive dental plates, bearing 4-6 acute ridges. Its skull roof was composed from massive, plate-like bones. In the central part of skull roof was localized an unossified fenestra. Most of the Ptychoceratodus findings are isolated dental plates, some associated with jaws. Other parts of skull or postcranial skeleton are relatively rarely found as fossils. The anatomy of skull is the best recognized in P. serratus, whereas less complete cranial material is available also for P. concinuus, P. phillipsi, and P. rectangulus. Although Ptychoceratodus is known exclusively from the Triassic and Jurassic, there were also Cretaceous specimens referred to this genus. However, they are more often regarded as representants of Metaceratodus. Ptychoceratodus is the only member of the family Ptychoceratodontidae. The first named species is P. phillipsi by Louis Agassiz in 1837 as a species of Ceratodus and later moved to Ptychoceratodus genus. Occurrences of Ptychoceratodus come mainly from Europe. However, occurrences from other continents suggest it was dispersed globally during the Triassic. After 2010, the new fossil material behind the Europe was reported from South America, India, and Greenland
Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones. The Olenellus-zone has traditionally marked the top of the Lower Cambrian, and is followed by the Eokochaspis zone.
Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic (Bajocian) to Lower Cretaceous (Barremian) ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter.
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.
The family Dactylioceratidae comprises Early Jurassic ammonite genera with ribbed and commonly tuberculate shells that resembled later Middle Jurassic stephanoceratids and Upper Jurassic perisphinctids. Shells may be either evolute or involute.
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.
Titanogomphodon is an extinct genus of diademodontid cynodonts from the Middle Triassic Omingonde Formation of Namibia. It is known from a single partial skull that was described in 1973 from the Omingonde Formation. The type and only species is Titanogomphodon crassus. At about 40 centimetres (16 in), the skull of Titanogomphodon was significantly larger than that of its closest relative, Diademodon. Its teeth are similar to those of another group of cynodonts called Traversodontidae, but the similarities are likely the result of convergent evolution. Aside from its larger size, Titanogomphodon differs from Diademodon in having a bony projection on the postorbital bar behind the eye socket.
Limnocyon is an extinct paraphyletic genus of limnocyonid hyaenodonts that lived in North America during the middle Eocene. Fossils of this animal have been found in California, Utah and Wyoming.
Viverravus is an extinct genus of placental mammals from extinct subfamily Viverravinae within extinct family Viverravidae, that lived in North America, Europe and Asia from the middle Paleocene to middle Eocene.
