| Humboldtichthys | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Gymnotiformes |
| Family: | Sternopygidae |
| Genus: | † Humboldtichthys Gayet & Meunier, 2000 |
| Species: | †H. kirschbaumi |
| Binomial name | |
| †Humboldtichthys kirschbaumi (Gayet & Meunier, 1991) | |
| Synonyms | |
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Humboldtichthys is an extinct genus of glass knifefishes from the Miocene Yecua Formation of Bolivia. A single species is currently recognized: Humboldtichthys kirschbaumi.
The earliest remains of gymnotiform electric fish were discovered in the Bolivian Yecua Formation 95 km west-northwest of Santa Cruz by petroleum geologists and easily recognized to belong to a gymnotiform fish based on several characteristic anatomical features. [1] From material collected, Gayet & Meunier described Ellisella kirschbaumi in 1991, unaware that the genus name was already occupied by a genus of soft coral ( Ellisella ). [2] The holotype specimen, RL 1596-4, represents an incomplete fragment of the animal, preserving the posterior margin of the skull and anterior elements of the body. An additional six fossils were also referred to the genus by Gayet & Meunier. As the name was already occupied however, the animal was given the genus name Humboldtichthys in the place of Ellisella in 2000 and the referred specimens were re-examined by Albert & Fink (2007). [1] In their examination they compared the holotype specimen with all 6 referred specimen and 3 further gymnotiform fossils from the Yeccua Formation. They concluded that the collected material represents more than one species, with most specimens potentially representing members of extant genera.
Humboldtichthys translates to "Humboldt's fish. Originally the name Ellisella kirschbaumi was meant to honor both American physiologist Max Mapes Ellis and German ichthyologist Frank Kirschbaum, who pioneered the research of gymnotiform growth and regeneration.
The holotype specimen preserves the right side of Humboldtichthys with a 5.5 cm long axis, including impressions of the opercle and preopercle as well as the anterior portion of the body. The surface of opercle and preopercle are lamellar with multiple deep radial striations. Although such striations are also present in modern members of Sternopygus, they are noticeably more pronounced in Humboldtichthys and the only diagnostic feature not called into question by Albert & Fink (2007). [1] The anterior limb of the preopercle is broad and crescent shaped, while its dorsal limb preserves a portion of a relatively broad preopercular-mandibular laterosensory canal. The entire preopercle is oriented oblique to the main axis of the head. The opercle is triangular in shape with its dorsal, posterior and ventral margins slightly convex. However poor preservation renders it difficult to determine the exact shape of these bones. The origin of the anal fin is located immediately behind the posterior margin of the operculum and the holotype specimen preserves 28 pterygiophores and 15 fin rays, all of which unbranched. The pectoral fin possesses a minimum of 10 fin rays with a posterior displacement of approximately 1-2 cm. Compared to the depth of the body the ribs are relatively short. [1]
In 1994 Gayet et al. hypothesized that Humboldtichthys represented a basal gymnotiform and sister taxon to all other gymnotiforms other than the family Apteronotidae. [2]
In their 2007 study, Albert & Fink score each knifefish specimen from the Yecua Formation individually due to the lack of overlapping diagnostic material and the fact that knifefish are known to occur alongside other knifefish genera, meaning that sharing a single locality may not be reason enough to assign them to a single specimen. They recovered one referred specimen as Gymnotiformes incertae sedis and 4 more specimens as members of Sinusoidea. The holotype specimen of Humboldtichthys was recovered as a sister taxon to the extant Sternopygus . One specimen is placed within Sternopygidae incertae sedis while the remaining three specimens analysed were all recovered as Sternopygus incertae sedis. [1]
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Humboldtichthys is known from the Bolivian Yecua Formation, which represents a humid to semi-arid environment close to the coast with a variety of bodies of water. Fossil remains, including stomach content from previously referred specimens, confirms the presence of both small bodied characids and catfish in addition to the knifefish fauna. Grass-like aquatic macrophytes have also been found. Albert & Fink suggest that the specific locality where Humboldtichthys and the other knifefish remains have been found may preserve what was once a slow moving terra firma (non floodplain) stream, a common habitat for multi-species gymnotiform assemblages. [1]
The Gymnotiformes are an order of teleost bony fishes commonly known as Neotropical knifefish or South American knifefish. They have long bodies and swim using undulations of their elongated anal fin. Found almost exclusively in fresh water, these mostly nocturnal fish are capable of producing electric fields to detect prey, for navigation, communication, and, in the case of the electric eel, attack and defense. A few species are familiar to the aquarium trade, such as the black ghost knifefish, the glass knifefish, and the banded knifefish.
The ghost knifefishes are a family, Apteronotidae, of ray-finned fishes in the order Gymnotiformes. These fish are native to Panama and South America. They inhabit a wide range of freshwater habitats, but more than half the species in the family are found deep in rivers where there is little or no light.
Glass knifefishes are fishes in the family Sternopygidae in the order Gymnotiformes. Species are also known as rattail knifefishes.
The Hypopomidae are a family of fishes in the order Gymnotiformes known as the bluntnose knifefish. They may also be called grass or leaf knifefishes. These electric fish are not often eaten, of little commercial importance, rarely kept as aquarium fish, and poorly studied; however, species in this family may constitute a significant fraction of the biomass in the areas they inhabit.
The Intermediate whiting, is a species of coastal marine fish of the smelt-whiting family Sillaginidae. The intermediate whiting ranges from the west coast of India to the Gulf of Thailand in the east, inhabiting silty substrates in shallow waters. First identified in 1977 from a specimen found in a fish market, the species has had little research performed on its biology, and is frequently misidentified as Sillago sihama or Sillago maculata intermediate whiting are commonly caught by fishermen throughout their range and are marketed fresh locally.
Magosternarchus is a genus of weakly electric knifefish in the family Apteronotidae, containing two species. They are endemic to Brazil, occurring in large river channels in the Amazon River basin. Both species are unusual benthic predators that specialize in biting off the tails of other knifefishes, and are characterized by their greatly enlarged jaws and teeth. Recent systematic studies indicate that both species should be included in Sternarchella instead of being placed in their own genus.
Sternarchogiton nattereri is a species of weakly electric knifefish in the family Apteronotidae. It is native to the Amazon River system and feeds on sponges. Unlike other members of the genus Sternarchogiton, there is pronounced sexual dimorphism in S. nattereri, with reproductively mature males developing strong external teeth on tips of their jaws. These males are so different from the females and juveniles that they were thought to be a different genus and species, the "tooth-lip knifefish" Oedemognathus exodon, for over 40 years.
Eigenmannia vicentespelaea is a species of weakly electric knifefish in the family Sternopygidae. Native to the São Domingos karst area in central Brazil, it is the only known knifefish to exclusively inhabit caves. Measuring up to 21 cm (8.3 in) long, E. vicentespelaea can be distinguished from its relatives by its translucent body and reduced or absent eyes. As some individuals retain well-developed eyes, this fish may have colonized caves only recently in evolutionary time.
Scymnosaurus is a dubious genus of therocephalian therapsids based upon various fossils of large early therocephalians. The genus was described by Robert Broom in 1903 with S. ferox, followed by S. watsoni in 1915 and a third, S. major, by Lieuwe Dirk Boonstra in 1954. Each of these species are considered nomen dubia today and based upon specimens belonging to two separate families of therocephalians. S. ferox and S. major represent specimens of Lycosuchidae incertae sedis, while S. watsoni is Scylacosauridae incertae sedis. Broom named a fourth species in 1907 from KwaZulu-Natal, S. warreni, though he later referred it to Moschorhinus as a valid species in 1932 but now is recognised as being synonymous with M. kitchingi.
Pariosternarchus amazonensis is a little-known species of weakly electric knifefish in the family Apteronotidae, and the only member of the genus Pariosternarchus. It is found in the main channel of the Amazon River in Brazil and Peru, likely near the bottom in deep, fast-moving water. This species is characterized by a wide head with a flat bottom, and very large sensory canals along the lower jaw. Like several other knifefishes found in deep river channels, it has reduced eyes, scales, and body pigmentation.
Cladistia is a clade of bony fishes whose only living members are the bichirs of tropical Africa. Their major synapomorphies are a heterocercal tail in which the dorsal fin has independent rays, and a posteriorly elongated parasphenoid.
Kyphosichthys is an extinct genus of basal actinopterygian bony fish known from the lower Middle Triassic (Anisian) marine deposits in Luoping, eastern Yunnan Province, southwestern China. The species is the first known fossil record of highly deep-bodied ginglymodians.
Japigny kirschbaum is a species of glass knifefish described in 2011 from the Approuague, Mana and Maroni rivers in French Guiana. It is the only member of its genus. It reaches up to 22 cm (8.7 in) in total length and is brownish-dusky with a pattern of dark-and-pale broad bands.
Sternopygus is a genus of glass knifefishes found in tropical and subtropical South America, and Panama. They inhabit a wide range of freshwater habitats, from fast-flowing rivers to essentially static waters in floodplains, and shallow habitats to the bottom of deep rivers. S. macrurus will even visit brackish mangrove to feed.
Cipactlichthys is a genus of extinct holostean fish from the Lower Cretaceous of Mexico. The only known species is Cipactlichthys scutatus.
Distocyclus conirostris is a species of glass knifefishes found in the deep waters of the Amazon basin, lower portions of the Potaro River and in major parts of the Rio Orinoco. They are typically relegated to flood basins, flooded forests and main river channels. They have often been found gathering in small groups around vegetation, indicating a social nature. The fish has semi-translucent, glass-like pectoral and anal fins. The main body is a ground-like color with a lighter head. The largest currently recorded specimen is 34.5 cm.
Gymnotus choco, commonly known as the cuchillo, is an electric knifefish. G. choco is distinguished from its cogenerate species group by a color pattern possessing pale yellow bands oriented obliquely, wherein the interband margins are wavy or even irregular; one to three Y-shaped dark bands occur on its body's posterior section; and its pale bands do not extend above the fish's lateral line on its body's anterior two-thirds. G. choco is most similar to G. paraguensis from the Pantanal in Brazil and Paraguay. From the latter, it is distinguished by having a narrower mouth, a more cylindrical body, and a longer preanal distance.
Otocephala is a clade of ray-finned fishes within the infraclass Teleostei that evolved some 230 million years ago. It is named for the presence of a hearing (otophysic) link from the swimbladder to the inner ear. Other names proposed for the group include Ostarioclupeomorpha and Otomorpha.
The Yecua Formation is a geological Formation in what is now Bolivia. Studies suggest that the Yecua Formation preserves a coastal setting with humid to semiarid floodplains, shorelines and tidal as well as shallow marine environments including marshes, streams, lakes and brackish bodies of water. There may have been a connection to the Amazon Basin or the Paranaense Sea.
Pentanogmius is an extinct genus of sail-finned ray-finned fish that lived during the Late Cretaceous in what is now Europe and the United States. Five species are currently recognized, 2 from Cenomanian to Turonian Europe and 3 better known species from Coniacian to Campanian North America. The American species inhabited large areas of the Western Interior Seaway, with fossil finds indicating a range from Texas and Alabama in the south to Manitoba, Canada, in the north.
