Slickheads, also known as nakedheads or smoothheads, are deep water fishes that belong to the family Alepocephalidae. They are most commonly found in the bathypelagic layer, which is approximately 3000m below the surface. They get their name from the lack of scales on their heads. Similarly, the scientific name is from the Greek ᾰ̓- (a-, "not"); λέπος (lepos, "scale"); and κεφαλή (kephalē, "head"). It has about 22 genera with ca. 96 species.
Scomber is a genus of ray-finned fish in the family Scombridae living in the open ocean found in Atlantic, Indian and Pacific Ocean. The genus Scomber and the genus Rastrelliger comprise the tribe Scombrini, known as the "true mackerels". These fishes have an elongated body, highly streamlined, muscular and agile. The eyes are large, the head is elongated, with a big mouth provided with teeth. They have two triangular dorsal fins, with some stabilizing fins along the caudal peduncle. The basic color is blue-green with a silvery white belly and a darker back, usually black mottled.
Echidnocephalus is an extinct genus of prehistoric halosaur known from the Late Cretaceous. It is the earliest known definitive member of the order Notacanthiformes.
Casierius is an extinct genus of marine ray-finned fish that lived during the Albian stage of the Early Cretaceous epoch. It was a relative of the modern bonefish in the extinct family Phyllodontidae, although some authorities consider it either a true albulid or a very early eel. It contains a single species, C. heckeli, known from the Glen Rose Formation near Hood County, Texas.
Enischorhynchus is an extinct genus of prehistoric marine ray-finned fish that lived during the Late Cretaceous. It contains a single species, E. dallasensis from the late Santonian or early Campanian-aged Austin Formation of southern Texas, USA. It was a member of the Plethodidae, a dominant family of nektonic fish during the mid-late Cretaceous. It shows close morphological similarities and may be related to Concavotectum and Bachea. It was likely an endemic of the southern Western Interior Seaway.
Laytonia is an extinct genus of prehistoric halosaur that lived in deep water off the North American Pacific Coast from the Zemorrian Epoch until during the Upper Miocene subepoch, when tectonic uplift effectively destroyed the genus' habitat by making the deep water too shallow.
Elonichthys is an extinct genus of prehistoric freshwater ray-finned fish known from the late Paleozoic. The genus sensu stricto contains three species known from the latest Carboniferous to the earliest Permian of freshwater ecosystems of Europe, but as a former wastebasket taxon, it contains many more dubiously-classified species from the Carboniferous and Permian of Europe, Greenland, South Africa, and North America.
Berycomorus is an extinct genus of prehistoric marine ray-finned fish that lived during the late Eocene epoch. It contains a single species, B. firdoussi, from the Pabdeh Formation of Iran.
Cyttoides is an extinct genus of prehistoric marine ray-finned fish that lived during the early Oligocene epoch in the western Paratethys Sea over Europe. It contains a single species, C. glaronensis from the Matt Formation of Canton Glarus, Switzerland. It was a zeiform related to the extant genus Cyttus.
Elpistoichthys is an extinct genus of prehistoric marine ray-finned fish, likely a teleosteomorph, that lived in Europe during the early Carnian stage of the Late Triassic epoch. It is known from the Reingrabener Schiefer formation of Austria.
Acentrophorus is an extinct genus of prehistoric freshwater and marine ray-finned fish from the Roadian to the Wuchiapingian of England, Germany (Kupferschiefer), Italy and Russia. There may also be a Triassic occurrence in Australia.
Aluvarus praeimperialis is an extinct ray-finned fish, known from two headless larval fossil specimens found in the Pabdeh Formation, a Late Eocene stratum from the Priabonian epoch, of what is now Iran. A. praeimperialis was originally thought to be a luvar, described as "Luvarus praeimperialis", as it was thought to be a predecessor to the modern luvar. A later reexamination of the specimens showed that they were too incomplete to demonstrate such a conclusion and had no clear exclusive shared traits with luvar, and were renamed "Aluvarus", meaning "not luvar" or "different than luvar". However, some authorities still retain it as a luvar.
Anaethalion is an extinct genus of prehistoric marine and freshwater ray-finned fish related to modern tarpons and ladyfish. It is known from the Late Jurassic to the Early Cretaceous of Europe and northeasterrn Asia, roughly encompassing the Tethys Ocean.
Diaphyodus is an extinct genus of prehistoric marine ray-finned fish, generally considered a drumfish, from the Late Paleocene and Eocene, and potentially to the mid-Oligocene of Europe and North America.
Davichthys is an extinct genus of prehistoric marine ray-finned fish related to modern ladyfish. It is known from the Late Cretaceous of southern Europe, the Middle East, and North Africa. It is one of the earliest known elopids.
Cylindracanthus is an extinct, enigmatic genus of marine ray-finned fish with fossils known throughout North America, Europe, Asia and Africa from the Late Cretaceous to the late Eocene, with potential Oligocene records and a possible Miocene record also known. It is exclusively known from its distinctive partial remains, which are long cylindrical bony spines that are usually considered rostrum fragments, as well as some associated teeth. These spines are abundant & widespread throughout this timespan, and are useful indicators of a nearshore marine environment, but the taxonomic identity of the fish is still highly uncertain and debated.
Hulettia is an extinct genus of ray-finned fish known from United States. This fish genus contains two species, H. americana and H. hawesi.
Elopoides is an extinct genus of prehistoric marine ray-finned fish known from the Early Cretaceous of Europe. It contains a single species, E. tomassoni, known from the late Albian of Aube, France. It is thought to be a stem-group megalopid, making it closely related to modern tarpons.
Palimphyes is an extinct genus of marine ray-finned fish known from the Paleogene period. It was a euzaphlegid, an extinct family of scombroid fish related to the escolars and snake mackerels.
Bathyprion, is a genus of deepwater marine ray-finned fish belonging to the family Alepocephalidae, the slickheads. Its only extant species is Bathyprion danae, the fangtooth smooth-head. This species is found in the Atlantic and western Pacific Oceans.
