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 more unusual representatives, such as the goblin shark and megamouth shark.
Cow sharks are a shark family, the Hexanchidae, characterized by an additional pair or pairs of gill slits. Its 37 species are placed within the 10 genera: Gladioserratus, Heptranchias, Hexanchus, Notidanodon, Notorynchus, Pachyhexanchus, Paraheptranchias, Pseudonotidanus, Welcommia, and Weltonia.
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.
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. At least 16 species are considered valid, with the largest members of the genus suggested to have grown up to 10 meters long. The youngest remains date to around 85 million years ago. A large number of remains have been found in the former Western Interior Seaway.
Anomoeodus is an extinct genus of prehistoric marine ray-finned fish belonging to the family Pycnodontidae. This genus primarily lived during the mid-to-late Cretaceous period, ranging from the Albian to the very end of the Maastrichtian age, and possibly into the Danian. The first fossils of Anomoeodus were described by Louis Agassiz in 1833, although they were described under Pycnodus. Some studies have recovered it as a wastebasket taxon.
Coelodus is an extinct genus of marine and possibly freshwater pycnodont fish. It contains only one definitive species, C. saturnusHeckel, 1854, from the Late Cretaceous of Slovenia. Other species from the Late Jurassic to the Eocene have also been attributed to this genus based on isolated dental elements, but their assignment to Coelodus is uncertain, and this genus likely represents a non-monophyletic wastebasket taxon. A potential diagnostic trait is a prearticular tooth row with three regular highly elongated teeth.
Cardabiodon is an extinct genus of large mackerel shark that lived about 95 to 91 million years ago (Ma) during the Cenomanian to Turonian of the Late Cretaceous. It is a member of the Cardabiodontidae, a family unique among mackerel sharks due to differing dental structures, and contains the two species C. ricki and C. venator. Cardabiodon fossils have been found in Australia, North America, England, and Kazakhstan. It was likely an antitropical shark that inhabited temperate neritic and offshore oceans between 40° and 60° paleolatitude, similar to the modern porbeagle shark.
Deccanolestes is a scansorial, basal Euarchontan from the Late Cretaceous (Maastrichtian) and Paleocene Intertrappean Beds of Andhra Pradesh, India. It may be closely related to Sahnitherium. Deccanolestes has been referred to Palaeoryctidae in the past, but recent evidence has shown that it is either the most basal Euarchontan, as the earliest known Adapisoriculid, or as a stem-afrotherian.
Gladioserratus is an extinct genus of cow shark. It contains three species:
Cretorectolobus is an extinct carpet shark. It was described by G.R. Case in 1978, and the type species is C. olsoni, which existed during the Campanian in Canada and the United States. Another species, C. gracilis, was described by Charlie J. Underwood and Mitchell in 1999, from the Hauterivian to Barremian strata of the Speeton Clay Formation of England. The species epithet refers to the shark's teeth, which Underwood and Mitchell described as gracile and narrow in form. A new species, C. robustus, was described from the Cenomanian of Canada by Underwood and Stephen L. Cumbaa in 2010.
Eostriatolamia is an extinct genus of sharks in the family Odontaspididae. It was described by Gluckman in 1980. A new species, E. paucicorrugata, was described from the Cenomanian of Canada by Charlie J. Underwood and Stephen L. Cumbaa in 2010.
Meristodonoides is an extinct genus of hybodont. The type species is M. rajkovichi, which was originally a species in the genus Hybodus. The species, along with other Hybodus species such as H. butleri and H. montanensis, was reassigned to Meristodonoides by Charlie J. Underwood and Stephen L. Cumbaa in 2010. The species is primarily known from remains from the Cretaceous of North America, spanning from the Aptian/Albian to Maastrichtian, making it one of the last surviving hybodont genera, though records of the genus likely extend back as far as the Late Jurassic, based on an undescribed skeleton from the Tithonian of England, and fragmentary teeth from the Kimmeridgian of Poland, England and Switzerland. Other remains of the genus are known from the Coniacian of England, the Aptian-Albian of France, and the Campanian of European Russia. The morphology of the teeth suggests an adaptation to tearing prey. Fossils from the Western Interior Seaway suggest that it preferred nearshore marine environments, being absent from deeper-water areas, with it likely also being able to tolerate brackish and freshwater conditions.
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.
Palaeocarcharodon, also known as the pygmy white shark, is a genus of shark within the family Otodontidae that lived about 61.7 to 55.8 Ma during the Paleocene. It currently contains a sole species P. orientalis.
Cardabiodontidae is an extinct family of lamniform sharks. Confirmed members of this family include Cardabiodon and Dwardius, both which are genera which existed in Australia, North America, and Europe during the Late Cretaceous period. It has been suggested that Parotodus could also belong to this family, but the authors that originally made this proposal expressed a weakening of rationale for it.
Archaeolamna is an extinct genus of mackerel sharks that lived during the Cretaceous. It contains three valid species which have been found in Europe, North America, and Australia. While it is mostly known from isolated teeth, an associated set of teeth, jaws, cranial fragments, and vertebrae of A. kopingensis is known from the Pierre Shale of Kansas. Teeth of A. k. judithensis were found with a plesiosaur skeleton with bite marks from the Judith River Formation of Montana. It was a medium-sized shark with an estimated total body length of 3–4 metres (9.8–13.1 ft).
Kenolamna is an extinct genus of mackerel shark from the Cretaceous period known only from isolated teeth. It is named in honor of Kenneth McNamara, former curator of Paleontology at the Western Australian Museum. It is tentatively placed in the family Otodontidae, and is closest in design to Cretalamna and Paleocarcharodon though it is unclear how closely related it is to either. Currently, it is a monotypic genus containing only the species K. gunsoni.
