| Echinochimaera Temporal range: Upper Mississippian, | |
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| Specimen of Echinochimaera meltoni | |
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| Suborder: | Echinochimaeroidei |
| Family: | Echinochimaeridae |
| Genus: | Echinochimaera Lund, 1977 [1] |
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Echinochimaera ("prickly chimaera") 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.
The genus' name derives from the Greek εχινό (echino) meaning spiny, and chimaera. It is assigned to the order Chimaeriformes. [1]
The two known Echinochimaera species lived in the Upper Mississippian (Serpukhovian). [3] Fossils of the species were found in the Bear Gulch Limestone in Montana, United States.
Both species have rounded bodies and paddle-like tails as well as large pectoral fins, two dorsal fins and a jaw fused to the braincase. [4] The paddle-like tails indicate that E. meltoni was likely not a predator nor a fast swimmer. [5] [6]
E. meltoni was first described by Richard Lund, an Adelphi University palaeontologist, [7] in 1977. [1] [3] The fossils found of E. meltoni have shown a great deal of sexual dimorphism, males being found to have a maximum 150mm body length while the maximum body length found in females was only 70mm (juveniles were 13-20mm). In general, the females only grew to about half the size of the males. [5] Males also had four pairs of spikes which may have been used to defend against predators and to identify the fish as male. [6]
There was a relative abundance of immature male fossils found, and that together with the significant sexual dimorphism indicate there was extreme sexual selection among the species. [5]
E. snyderi was described, like E. meltoni, by Richard Lund. It was described in 1988 based on juvenile specimens, all with a body length under 90mm. E. snyderi differs from E. meltoni in fin detail as well as jaw shape and teeth near the front edge of the face rather than a tooth plate, in mature specimens later found its mature size was found to be larger than E. meltoni. [8]
Halosaurs are eel-shaped fishes found only at great ocean depths. As the family Halosauridae, halosaurs are one of two families within the order Notacanthiformes; the other being the deep-sea spiny eels, Notacanthidae. Halosaurs are thought to have a worldwide distribution, with some 17 species in three genera represented. Only a handful of specimens have been observed alive, all in chance encounters with Remotely operated underwater vehicles.
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.
Belantsea is a genus of extinct petalodontid cartilaginous fish that lived during the Lower Carboniferous, about 350 million years ago. Its fossils are found in the Bear Gulch Limestone lagerstätte. Its body was leaf-shaped, with muscular fins and a small tail. Such a body plan would allow for great maneuverability, but at the cost of speedy cruising. Its few, large, triangular teeth formed a beak-like arrangement that allowed it to graze bryozoans, sponges, crinoids, and other encrusting animals. The genus contains two species, B. montana and B. occidentalis.
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.
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.
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.
Harpagofututor is an extinct genus of eel-like cartilaginous fish from the Early Carboniferous (Mississippian) Bear Gulch Limestone of Montana in North America.
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.
Debeerius is a genus of chondrichthyan from the Mississippian age Bear Gulch Limestone of Montana, United States. It is named after Gavin de Beer. One species, D. ellefseni, is known, which is preserved in very fine detail. Melanin preserved in fossils of D. ellefseni indicates it possessed dark stripes down the length of its body. The jaw suspension of Debeerius was autodiastylic.
Guildayichthyidae is a prehistoric family of marine fish from the Mississippian Bear Gulch Limestone of Montana. It is the only family in the order Guildayichthyiformes. Guildayichthyids possess an uncommon mixture of primitive and modern characteristics in their skull bones.
Discoserra is a prehistoric ray-finned fish from the Mississippian of the Bear Gulch Limestone in Montana. It is a member of the Guildayichthyiformes with a round body and a skull possessing primitive and modern traits. Discoserra is about 60 mm long. In 2006, Discoserra was hypothesized to be a stem neopterygian, although it has alternatively been placed in Cladistia along with other Guildayichthyiformes.
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.
Aesopichthys is an extinct genus of palaeoniscoid ray-finned fish from North America. Its fossils are currently only known from the Bear Gulch Limestone located in central Montana which dates to the late Mississippian, also known as the Serpukhovian. It was a deep-bodied member of the group, though not to the extent of what is seen in genera like Platysomus. It possessed a short, blunt snout along with partially-webbed fins. There is only a single species in the genus being A. erinaceus.
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.