Requiem sharks are sharks of the family Carcharhinidae in the order Carcharhiniformes. They are migratory, live-bearing sharks of warm seas and include such species as the bull shark, lemon shark, blacktip shark, and whitetip reef shark.
The Hexanchiformes are a primitive order of sharks, numbering just seven extant species in two families. Fossil sharks that were apparently very similar to modern sevengill species are known from Jurassic specimens.
The Lamniformes are an order of sharks commonly known as mackerel sharks. It includes some of the most familiar species of sharks, such as the great white as well as less familiar ones, such as the goblin shark and megamouth shark.
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively.
Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks, rays, skates, and sawfish. Members of this subclass are characterised by having five to seven pairs of gill slits opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil.
Squalicorax, commonly known as the crow shark, is a genus of extinct lamniform shark known to have lived during the Cretaceous period. The genus had a global distribution in the Late Cretaceous epoch. Multiple species within this genus are considered to be wastebasket taxon due to morphological similarities in the teeth.
Cretoxyrhina is an extinct genus of large mackerel shark that lived about 107 to 73 million years ago during the late Albian to late Campanian of the Late Cretaceous. The type species, C. mantelli, is more commonly referred to as the Ginsu shark, first popularized in reference to the Ginsu knife, as its theoretical feeding mechanism is often compared with the "slicing and dicing" when one uses the knife. Cretoxyrhina is traditionally classified as the likely sole member of the family Cretoxyrhinidae but other taxonomic placements have been proposed, such as within the Alopiidae and Lamnidae.
Scapanorhynchus is an extinct genus of goblin shark that lived during the Cretaceous period, from the Aptian to the end of the Maastrichtian. Later records, such as those from the Miocene assigned to the species S. subulatus, are highly dubious and may be misidentified sand sharks.
Isurus is a genus of mackerel sharks in the family Lamnidae, commonly known as the mako sharks. They are largely pelagic, and are fast, predatory fish capable of swimming at speeds of up to 50 km/h (31 mph).
Ptychodus is a genus of extinct large durophagous (shell-crushing) lamniform sharks from the Cretaceous period, spanning from the Albian to the Campanian. Fossils of Ptychodus teeth are found in many Late Cretaceous marine sediments worldwide.
Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and rays (Neoselachii) as part of the clade Euselachii. They are distinguished from other chondrichthyans by their distinctive fin spines and cephalic spines present on the heads of males. An ecologically diverse group, they were abundant in marine and freshwater environments during the late Paleozoic and early Mesozoic, but were rare in open marine environments by the end of the Jurassic, having been largely replaced by modern sharks, though they were still common in freshwater and marginal marine habitats. They survived until the end of the Cretaceous, before going extinct.
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.
Lonchidion is a genus of extinct hybodont in the family Lonchidiidae. The genus first appears in the fossil record during the Middle Triassic (Ladinian) and was among the last surviving hybodont genera, with its youngest known fossils dating to the very end of the Cretaceous (Maastrichtian).
Cretalamna is a genus of extinct otodontid shark that lived from the latest Early Cretaceous to Eocene epoch. It is considered by many to be the ancestor of the largest sharks to have ever lived, such as Otodus angustidens, Otodus chubutensis, and Otodus megalodon.
The New Egypt Formation is a Late Cretaceous geologic formation of the Monmouth Group in New Jersey, United States.
Mcmurdodus is an extinct genus of chondrichthyan belonging to the family Mcmurdodontidae. It contains one species, Mcmurdodus featherensis, from the Middle Devonian of Antarctica. The Australian species M. whitei was previously included in the genus too, but was moved to a new genus, Maiseyodus, in 2021.
Sclerorhynchoidei is an extinct suborder of rajiform rays that had long rostra with large denticles similar to sawfishes and sawsharks. This feature was convergently evolved, recently proposed as 'pristification', and their closest living relatives are actually skates. While they are often called "sawfishes", sawskates is a more accurate common name proposed in 2021 for sclerorhynchoids, which has been subsequently used by other researchers.
Synechodontiformes is an extinct order of prehistoric shark-like cartilaginous fish, known from the Permian to the Paleogene. They are considered to be members of Neoselachii, the group that contains modern sharks and rays.
Archaeogaleus is an extinct genus of requiem shark from the Cretaceous period. It is known only from the species A. lengadocensis. It was described from the Valanginian stage of France. The specific epithet refers to Lengadòc, the region where Occitan was historically spoken. It is the oldest known requiem shark and has a presumed dentition similar to the modern form Scoliodon.
Antrigoulia is an extinct genus of palaeospinacid shark from the Cretaceous period. It is named after a farm in the vicinity of the type locality called Mas d’Antrigoule. It is known from a single species consisting of isolated teeth from the Valanginian of France, A. circumplicata. The name is derived from the concentric folds on the labial side of its teeth.
