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.
Holocephali, sometimes given the name Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. The only living holocephalans are the chimaeras (Chimaeriformes), though during the late Paleozoic Holocephali was much more diverse, including an array of forms including those considerably different from modern Chimaeriformes, including shark-like predatory forms and slow, durophagous fish.
Stethacanthus is an extinct genus of shark-like cartilaginous fish which lived from the Late Devonian to Late Carboniferous epoch, dying out around 298.9 million years ago. Fossils have been found in Australia, Asia, Europe and North America.
The Bear Gulch Limestone is a limestone-rich geological lens in central Montana, renowned for the quality of its marine fossils from the late Mississippian subperiod, about 324 million years ago. It is exposed over a number of outcrops northeast of the Big Snowy Mountains, and is often considered a component of the more widespread Heath Formation. The Bear Gulch Limestone reconstructs a diverse, though isolated, marine ecosystem which developed near the end of the Serpukhovian age in the Carboniferous period. It is a lagerstätte, a particular type of rock unit with exceptional fossil preservation of both articulated skeletons and soft tissues. Bear Gulch fossils include a variety of fish, invertebrates, and algae occupying a number of different habitats within a preserved shallow bay.
Symmoriiformes is an extinct order of cartilaginous fish. Originally named Symmoriida by Zangerl (1981), the name has since been corrected to Symmoriiformes to avoid confusion with a family. The symmoriiform fossils record begins during the late Devonian, and most had become extinct by the start of the Permian, with the genus Dwykaselachus from the Artinskian-Kungurian of South Africa being the latest known uncontroversial occurrence. Teeth described from the Valanginian of France and Austria indicate that members of the family Falcatidae might have survived until the Early Cretaceous; however, it has since been proposed that these teeth more likely belonged to neoselachian sharks.
Falcatus is an extinct genus of falcatid chondrichthyan which lived during the early Carboniferous Period in Bear Gulch bay in what is now Montana.
Stethacanthidae is an extinct family of prehistoric sharks. It is estimated to have existed approximately between 380 and 300 million years ago. Members of this family are noted for their peculiar dorsal fin.
Petalodontiformes is an extinct order of marine cartilaginous fish related to modern day chimaera found in what is now the United States of America and Europe.
Netsepoye is an extinct genus of cartilaginous fish distantly related to the modern order Chimaeriformes, containing the single species Netspoye hawesi. It lived more than 320 million years ago during the Late Mississippian.
Echinochimaera is an extinct genus of chimaeriform fish, known from the Lower Carboniferous Bear Gulch Limestone in Montana, United States. It is one of the earliest Chimaeriformes known.
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.
Iniopterygiformes is an extinct order of cartilaginous fish known only from the Carboniferous period of the United States. Iniopterygians are characterized by large, superficially wing-like pectoral fins positioned upwards behind the head, from which the name of the group is derived. Iniopterygians are also noted to possess proportionally large skulls and eyes, armor plates composed of dentin, and "tooth-whorls" of fused teeth. Their elongated pectoral fins bore large, denticle-covered spines, and they are thought to have used them to swim using a "flying" motion. The iniopterygians were comparatively small chondrichthyans, with the largest species reaching only 50 cm (20 in) in length.
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.
Thrinacodus is an extinct genus of basal elasmobranch, found worldwide from the Late Devonian-Lower Carboniferous. The type species is Thrinacodus nanus. Most species are only known from their tricuspid teeth. T. gracia, originally placed in the separate genus Thrinacoselache from the Serpukhovian-aged Bear Gulch Limestone, of what is now Montana, is known from full body impressions, showing a long, slender eel-like body up to a metre in length, with an elongate rostrum. Stomach contents of T. gracia include remains of crustaceans and small chondrichthyan fish. It is a member of the Phoebodontiformes.
Bealbonn is an extinct genus of holocephalian from the Carboniferous. It is known by a singular species, B. rogaire. It is known from the Serpukhovian-aged lagerstätte of the Bear Gulch Limestone of Montana, United States. It is one of the genera included in the family Gregoriidae.
Gregoriidae is an extinct family of early chondrichthyans from the Carboniferous period. It currently includes three described genera: Gregorius, Srianta, and Bealbonn. This family includes remains formerly ascribed to "Desmiodus," which is now considered a nomen vanum. The relationships between the included genera are not entirely clear. Fossils are known from Serpukhovian-aged formations including the Bear Gulch Limestone and Surprise Canyon Formation.
Squatinactis is a genus of extinct elasmobranch chondrichthyan known from the Carboniferous aged Bear Gulch Limestone in Montana. This fish was discovered in 1974 by Richard Lund. The type specimen, named CMNH 46133, consists of a brain case, poorly preserved jaws and gills, a pectoral fin, and a partial vertebral axis. This creatures most startling feature were its broad pectoral fins which resembled those of stingrays and angel sharks (Squatina). The holotype specimen has about 15 teeth in its jaw. This creature is named after the angel shark. Remains found in the South Urals of Russia and the Eyam Limestone of Derbyshire, England, have been tentatively identified as those belonging to S. caudispinatus.
Heteropetalus is a genus of chondrichthyan from the Mississippian age Bear Gulch Limestone of Montana, United States. One species, H. elegantulus, is known. Known fossils of Heteropetalus are exceptionally well preserved, displaying details of the soft tissue anatomy such as an opercular cover over the gills.
Debeeriidae is a family of holocephalan fishes from the Mississippian subperiod of the Carboniferous. It is the only family of the order Debeeriiformes. It is named after the type genus, Debeerius, which itself is named in honor of Gavin de Beer. Members of this family and order possess a spine on the first dorsal fin, an opercular cover over the gills, and an autodiastylic (two-jointed) jaw suspension. Both genera in the family are known from exceptionally well-preserved specimens found in the Bear Gulch Limestone member of the Heath Formation.
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.
