Chondrichthyes is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or bony fish, which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates.
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last two names are also applied to Opisthoproctidae and 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.
Cladoselache is an extinct genus of shark-like chondrichthyan from the Late Devonian (Famennian) of North America. It was similar in body shape to modern lamnid sharks, but was not closely related to lamnids or to any other modern (selachian) shark. As an early chondrichthyan, it had yet to evolve traits of modern sharks such as accelerated tooth replacement, a loose jaw suspension, enameloid teeth, and possibly claspers.
Dapedium is an extinct genus of primitive marine neopterygian ray-finned fish. The first-described finding was an example of D. politum, found in the Lower Lias of Lyme Regis, on the Jurassic Coast of England. Dapedium lived in the Late Triassic to the Middle Jurassic period, from the late Norian to the early Aalenian.
Ischyodus is an extinct genus of chimaera. It is the most diverse and long-lived chimaera genus, with over 39 species found worldwide spanning over 140 million years from the Middle Jurassic to the Miocene. Almost all species are only known from tooth plates, with the exception of the Jurassic species I. quenstedti. Complete specimens of I. quenstedti from the Late Jurassic of Germany most closely resemble the genus Callorhinchus amongst living chimaera genera. It is sometimes placed in the "Edaphodontidae", a unclearly defined group of chimaera with an uncertain position within the clade, while other authors place it into Callorhinchidae along with Callorhinchus, a position that has been supported by at least some phylogenetic analyses. It is suggested therefore to probably have had a similar ecology to living Callorhinchus.
The silver chimaera, or ginzame, is a species of holocephalan in the family Chimaeridae. They are found in the deep sea along the coast of East Asia, from Japan to Indonesia. They are chondrichthyans, closely related to sharks and rays, which means that they have a fully cartilaginous skeleton with no true bones.
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.
Chondrenchelys is an extinct genus of cartilaginous fish and the earliest member of Holocephali known from complete skeletons. Chondrenchelys would have been quite a relatively medium-sized fish with an elongated body up to 18 cm (0.59 ft)in length, it had a dorsal fin which was indeed long and a body which tapered to a point. Chondrenchelys had one large pair, one middle-sized pair, and three small pair of tooth plates in each jaw. The genus name derives from the Greek word χόνδρος, meaning “gristle” or “cartilage”, and ἔγχελυς, meaning “eel”. The speciea name, problematicus, is likely derived from the lack of scales setting it apart from all other fish known at the time of discovery.
Squaloraja is an extinct genus of ray-like marine chimaeriform fish from the Early Jurassic of Europe.
The Allgäu Formation is a geologic formation in Austria, Germany and Slovakia. It preserves fossils dating back to the Hettangian to Sinemurian stages of the Early Jurassic period, or Raricostatum to Obtusum in the regional stratigraphy. Initially and formally defined by Jacobshagen (1965). The Allgäu Formation is formerly known as spotted marls (Lias-Fleckenmergel) and spotted marly limestones (Fleckenkalk). The formation is represented by dark-grey bioturbated limestones and marlstone interbeds. It represents basinal hemipelagic facies common in Alpine Tethys regions of Alps, Carpathians and other mountain ranges. Several horizons of the formation are particularly rich in ammonite fauna.
Ornithoprion is a genus of extinct cartilaginous fish in the family Caseodontidae. The only species, O. hertwigi, lived during the Moscovian stage of the Pennsylvanian, between 315.2 to 307 million years ago, and is known from black shale deposits in what is now the Midwestern United States. The discovery and description of Ornithoprion, performed primarily via radiography, helped clarify the skull anatomy of eugeneodonts; a group which includes O. hertwigi and which were previously known primarily from isolated teeth. The genus name, which is derived from the ancient Greek órnith- meaning 'bird' and príōn meaning 'saw', was inspired by the animal's vaguely bird-like skull and the saw-like appearance of the lower teeth. The species name honors Oscar Hertwig.
Paracestracion is an extinct genus of heterodontiform sharks from Early Jurassic to Early Cretaceous-aged rocks of England, France, Germany and Luxembourg. The genus was first described in 1911 by Ernst Hermann Friedrich von Koken in Karl Alfred von Zittel.
Agkistracanthus is an extinct genus of chimaera from the Mesozoic era. It currently contains a single species, A. mitgelensis. It is known from the Rhaetian to Hettangian epochs, spanning the transition from the Triassic to Jurassic period. Fossils from this genus are known from Switzerland, Austria, and Britain. It is known mostly from isolated and fragmentary material, including fin spines as well as palatine, symphyseal, and mandibular structures.
Bathytheristes is an extinct genus of chimaera from the late Early Jurassic epoch of the Jurassic Period. Its name roughly translates to "Reaper of the deep." It is known from a single species, B. gracilis. It was discovered in the early Toarcian-aged Posidonia Shale Formation of Ohmden, Germany. The specific epithet refers to the slender of the tooth plate in this species. It is related to the modern elephantfish.
Necrotauliidae is an extinct family Mesozoic Amphiesmenoptera. While previously considered a paraphyletic grouping of "basal Trichoptera, basal Lepidoptera, and advanced stem-Amphiesmenoptera", they have recently been considered early diverging caddisflies. Other authors have considered them to be basal amphiesiopterans.
Orthophlebiidae is an extinct family of scorpionflies known from the Triassic to Cretaceous, belonging to the superfamily Panorpoidea. The family is poorly defined and is probably paraphyletic, representing many primitive members of Panorpoidea with most species only known from isolated wings, and has such been considered a wastebasket taxon.
This list of fossil fish research presented in 2025 is a list of new fossil taxa of jawless vertebrates, placoderms, 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 2025.
Chimaeropsis is an extinct genus of cartilaginous fish related to modern chimaeras, known from the Jurassic of Europe.
Chondrenchelyiformes is an extinct order of holocephalan cartilaginous fish, known from the Early Carboniferous of Europe and North America. There are currently two recognised genera known from largely complete remains, Chondrenchelys from the Visean of Scotland, and Harpagofututor from the Serpukhovian aged Bear Gulch Limestone of Montana, United States. Both genera have elongate, eel-like bodies, with their mouths having tooth plates similar to those of living chimaeras, to which they share numerous anatomical similarities indicating a close relationship. Isolated tooth plates assigned to the genus Platyxystrodus likely belong to members of the family, which would extend the range of the group into the late Carboniferous.
