The whale shark is a slow-moving, filter-feeding carpet shark and the largest known extant fish species. The largest confirmed individual had a length of 18.8 m (61.7 ft). The whale shark holds many records for size in the animal kingdom, most notably being by far the most massive living non-mammalian animal. It is the sole member of the genus Rhincodon and the only extant member of the family Rhincodontidae, which belongs to the subclass Elasmobranchii in the class Chondrichthyes. Before 1984 it was classified as Rhiniodon into Rhinodontidae.
The megamouth shark is a species of deepwater shark. Rarely seen by humans, it measures around 17 ft (5.2 m) long and is the smallest of the three extant filter-feeding sharks alongside the relatively larger whale shark and basking shark. Since its discovery in 1976, fewer than 100 specimens have been observed or caught. Like the other two planktivorous sharks, it swims with its mouth wide open, filtering water for plankton and jellyfish. It is recognizable from its large head with rubbery lips. The megamouth is so unlike any other type of shark that it is usually considered to be the sole extant species in the family Megachasmidae, though some scientists have suggested it may belong in the family Cetorhinidae.
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.
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.
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.
Megachasma is a genus of mackerel sharks. It is usually considered to be the sole genus in the distinct family Megachasmidae, though suggestion has been made that it may belong in the family Cetorhinidae, of which the basking shark is currently the sole extant member. Megachasma is known from a single living species, Megachasma pelagios.
Thysanoessa raschii, sometimes known as Arctic krill, is one of the most common euphausiid species of the subarctic and Arctic seas. They may reach 20–25 millimetres (0.8–1.0 in) long, and are sexually mature above 14 mm (0.6 in).
Ptychodus is a genus of extinct durophagous (shell-crushing) sharks from the Late Cretaceous. Fossils of Ptychodus teeth are found in many Late Cretaceous marine sediments. There are many species among the Ptychodus that have been uncovered on all the continents around the globe. Such species are Ptychodus mortoni, P. decurrens, P. marginalis, P. mammillaris, P. rugosus and P. latissimus to name a few. They died out approximately 85 million years ago. A large number of remains have been found in the former Western Interior Seaway. A 2016 publication found that Ptychodus are likely true sharks belonging to Selachimorpha, rather than hybodonts or batoids as previously thought. Their life history coincides with the typical life of many other large sharks: they lived relatively long lives and were slow growing and produced large offspring and small litters.
Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like chondrichthyans, which existed from the late Devonian to the Late Cretaceous. They form the group of Elasmobranchii closest to neoselachians, the clade of modern sharks and rays. Hybodonts were named and are distinguished based on their conical tooth shape. They are also noted for the presence of a spine on each of their two dorsal fins. 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.
Bonnerichthys is a genus of fossil fishes within the family Pachycormidae that lived during the Coniacian to Maastrichtian stage of the Late Cretaceous. Fossil remains of this taxon were first described from the Smoky Hill Member of the Niobrara Chalk Formation of Kansas, and additional material was later reported from the Pierre Shale, Mooreville Chalk, Demopolis Chalk, Wenonah Formation, and Moreno Formation, among other localities. It grew to at least 5 metres (16 ft) in total body length, substantially less than the related Leedsichthys from the Jurassic which likely grew up to 16.5 metres (54 ft).
Rhinconichthys is an extinct genus of bony fish which existed during the Cenomanian stage of the Late Cretaceous.
Protopsephurus is an extinct genus of paddlefish containing the single species Protopsephurus liui, known from the Yixian Formation in Liaoning, northern China from the Barremian to Aptian ages of the Early Cretaceous period around 125-120 million years ago. It is currently the oldest and most basal paddlefish known.
Nanocetorhinus is an extinct genus of sharks in the subclass Neoselachii. The type and only described species is N. tuberculatus, which existed in what is now Slovakia during the Miocene epoch, and was described by Charlie J. Underwood and Jan Schlogl in 2011. It was described from 28 fossilized teeth.
A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Planktivorous organisms encompass a range of some of the planet's smallest to largest multicellular animals in both the present day and in the past billion years; basking sharks and copepods are just two examples of giant and microscopic organisms that feed upon plankton. Planktivory can be an important mechanism of top-down control that contributes to trophic cascades in aquatic and marine systems. There is a tremendous diversity of feeding strategies and behaviors that planktivores utilize to capture prey. Some planktivores utilize tides and currents to migrate between estuaries and coastal waters; other aquatic planktivores reside in lakes or reservoirs where diverse assemblages of plankton are present, or migrate vertically in the water column searching for prey. Planktivore populations can impact the abundance and community composition of planktonic species through their predation pressure, and planktivore migrations facilitate nutrient transport between benthic and pelagic habitats.
Eorhincodon is an invalid genus of requiem shark from the Late Eocene of Xinjiang, China, originally described as a whale shark. It is currently considered a junior synonym of Rhizoprionodon. The genus was originally erected by Li (1997) to include the species Eorhincodon tianshanensis, but Nessov (1999) used the preoccupied genus in a different paleontological context to include an unrelated species, E. casei, from Late Cretaceous Russian marine strata. A new genus, Pseudomegachasma, was erected in 2015 for E. casei to be transferred into.
Johnlongia is an extinct genus of sand shark from the Cretaceous period. It contains two described species, J. parvidens and J. allocotodon, and possibly a third unnamed species from the Niobrara Chalk. It is presumed piscivorous; however, it forms a clade with an early filter-feeding shark genus, Pseudomegachasma.
Xenodens is an extinct genus of marine lizard belonging to the mosasaur family. It currently contains a single species, X. calminechari, which is known from Late Maastrichtian phosphate deposits in the Ouled Abdoun Basin, Morocco. Its closest known relative is believed to be the durophagous Carinodens.
Aquilolamna is an extinct genus of shark-like elasmobranch from the Late Cretaceous (Turonian)-aged Agua Nueva Formation of Mexico. It is currently known to contain only one species, A. milarcae, also known as the eagle shark, and it is classified in its own family Aquilolamnidae, which has been tentatively assigned to the mackerel sharks.
This list of fossil fish research presented in 2021 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes, and other fishes that were described during the year, as well as other significant discoveries and events related to paleoichthyology that occurred in 2021.
Platylithophycus is an extinct genus of elasmobranchs that lived during the Late Cretaceous. It is known from a single specimen from the Niobrara Formation of Kansas, United States. It was originally identified as the fronds of a codiacean alga, then later as the cuttlebone of a cuttlefish. It was most recently reidentified as the gill arches and rakers of an elasmobranch of uncertain affinities. It might have been a filter feeding mackerel shark related to Aquilolamna.
