The Anostomidae are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

es that belong to the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Characiformes Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A.: "Relationsh ...

. Closely related to the Chilodidae and formerly included with them, the Anostomidae contain about 150 described

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. Commonly known as anostomids, they are found in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

s from the Río Atrato in northernmost

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

to warm-

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

central

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

; they are of

Amazon Amazon most often refers to: * Amazon River, in South America * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon (company), an American multinational technology company * Amazons, a tribe of female warriors in Greek myth ...

origin, with few found west of the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

(mainly in

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

and

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

). Their

scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

approximately means "mouth on top", from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

''áno-'' (ἄνω) "up" (as an

adverb An adverb is a word or an expression that generally modifies a verb, an adjective, another adverb, a determiner, a clause, a preposition, or a sentence. Adverbs typically express manner, place, time, frequency, degree, or level of certainty by ...

) + ''stóma'' (στόμᾶ) "mouth", in reference to the arrangement of these fishes' mouth opening.FishBase (2004), Sidlauskas & Vari (2008)

Description

Anostomids have elongated bodies ranging from in length; their shape varies between

fusiform Fusiform (from Latin ''fusus'' ‘spindle’) means having a spindle (textiles), spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon (geometry), lemon-shape, but often implies a focal broadening of a ...

and deeper-bodied, but even the latter are only moderately laterally. They have elongated, tapering heads with rather long, straight snouts, and small apical to upturned mouths immediately at or near the snout tip. This family contains many headstanders, which habitually swim with their heads pointing from 45° up to 90° downwards; most feed on

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s near the bottom, while others also eat

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

and

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s picked up from river- or lakebeds. Adults guard the eggs after

spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...

. Anostomidae are generally considered edible, and some of the larger species are caught for food on a regular basis, much like large

Leuciscinae Leuciscinae is a subfamily of freshwater Actinopterygii, ray-finned fishes belonging to the Family (biology), family Leuciscidae, which includes the fishes known as daces, chubs, shiners and minnows. The fishes in this subfamily are mainly found i ...

(which are superficially similar

Cypriniformes Cypriniformes is an order of ray-finned fish, which includes many families and genera of cyprinid ( carps and their kin) fish, such as barbs, loaches, botias, and minnows (among others). Cypriniformes is an "order-within-an-order", placed ...

) are in the temperate

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

.Weitzman & Vari (1998), FishBase (2004), Sidlauskas & Vari (2008) Their

jaw The jaws are a pair of opposable articulated structures at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth ...

s are rather short, with the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

ry bone small and excluded from the mouth opening, while the ascending process of the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

is triangular in overall shape and robustly developed. One row of six or eight curved teeth occur in each jaw, arranged by length in a step-like fashion, with the front teeth being the longest; the

pharyngeal teeth Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species otherwise lacking teeth.gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

openings are small, with the gill membranes firmly joined to the

isthmus An isthmus (; : isthmuses or isthmi) is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated. A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea count ...

; the

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

between the interopercle and the mouth is elongated and the interopercle is clearly separated from the retroarticular. On the sides of the

preopercle The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. Anatomy The opercular series contains four bon ...

is a large, elongated protrusion, where the powerful jaw adductor muscles attach. The third epibranchial gill arch has a curved

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

process which extends medially over the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

surface of the fourth infrapharyngobranchial arch. The

circumorbital In scaled reptiles, the ocular scales are those forming the margin of the eye.Wright AH, Wright AA. 1957. ''Handbook of Snakes''. Comstock Publishing Associates (7th printing, 1985). 1105 pp. . The name originates from the term which is Latin f ...

bone series is complete and includes a

supraorbital bone Supraorbital refers to the region immediately above the eye sockets, where in humans the eyebrows are located. It denotes several anatomical features, such as: *Supraorbital artery *Supraorbital foramen * Supraorbital gland *Supraorbital nerve *Su ...

, and at least four, often more, of the forward

rib In vertebrate anatomy, ribs () are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the ...

s are united by two or more inter costal ligaments. The

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

is complete, contains 33-44 perforated scales, and runs along the midline of the body. The

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

bears a short lateral-line canal ending at or shortly behind mid-length, and altogether the lateral-line canals of the head are divided into at least two

ossified Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

tubes. All anostomids have an

adipose fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only b ...

; their

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

contains one and 11, the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

one and 9, and the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s one and 8-9 hard and soft rays, respectively.

Systematics and evolution

This family is in all probability

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

as traditionally defined. Several attempts to delimit

subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zool ...

have taken place, and several of the proposed groupings indeed correspond to

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

s within this family. '' Leporellus'' has long been recognized as the basal-most living anostomid genus, due to its many

plesiomorph In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral Phenotypic trait, character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorph ...

ies shared with the Chilodidae and its peculiar

apomorph In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ha ...

ies, and separated as a

subfamily by some. A large clade of "modern" genera was treated as Anostominae by some authors; others considered that subfamily more inclusive.Sidlauskas & Vari (2008) The latter view was later found to be incorrect, as it includes a large number of lineages that are really basal members of the family and should not be treated as a subfamily. More recent studies, incorporating phylogenetic evidence, have divided up the family into three subfamilies. Several genera ('' Megaleporinus'', '' Insperanos'', and '' Brevidens'') have also been split out of ''Leporinus'' to maintain it as a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

genus.

Genera

The genera of Anostomidae are: * Subfamily Leporellinae Eigenmann, 1910 (striped tail headstanders) ** Genus '' Leporellus'' Lütken, 1875 (four species) * Subfamily Anostominae Günther, 1864 (slender headstanders) ** Genus '' Anostomus''

Scopoli Giovanni Antonio Scopoli (sometimes Latinized as Johannes Antonius Scopolius) (3 June 1723 – 8 May 1788) was an Italian physician and naturalist. His biographer Otto Guglia named him the "first anational European" and the "Linnaeus of the Au ...

, 1777 (five species) ** Genus '' Gnathodolus''

Myers Myers as a surname has several possible origins, e.g. Old French ("physician"), Old English ("mayor"), and Old Norse ("marsh"). People * Abram F. Myers (1889–after 1960), chair of the Federal Trade Commission and later general counsel and b ...

, 1927 (one species) ** Genus '' Petulanos'' Sidlauskas &

Vari Vari () is a southern suburb of Athens and former municipality in East Attica, Greece along the Athens coast. The ancient Athenian deme of Anagyrous was situated here. Since the 2011 local government reform it is part of the municipality Vari-Vo ...

, 2008 (three species) ** Genus '' Pseudanos'' Winterbottom, 1980 (four species; paraphyletic?) ** Genus '' Sartor''

& de Carvalho, 1959 (three species) ** Genus '' Synaptolaemus''

& Fernández-Yépez, 1950 (two species) * Subfamily Leporininae Eigenmann, 1912 ** Genus '' Abramites'' Fowler, 1906 (two species) ** Genus '' Anostomoides'' Pellegrin, 1909 (three species) ** Genus '' Brevidens'' Birindelli, Sidlauskas & Melo, 2025 (one species) ** Genus '' Hypomasticus''

Borodin Alexander Porfiryevich Borodin (12 November 183327 February 1887) was a Russian Romantic composer and chemist of Georgian–Russian parentage. He was one of the prominent 19th-century composers known as " The Five", a group dedicated to prod ...

, 1929 (seven species) ** Genus '' Insperanos'' Assega, Sidlauskas & Birindelli, 2021 (one species) ** Genus '' Laemolyta''

Cope A cope ( ("rain coat") or ("cape")) is a liturgical long mantle or cloak, open at the front and fastened at the breast with a band or clasp. It may be of any liturgical colour. A cope may be worn by any rank of the Catholic or Anglican clerg ...

, 1872 (9 species) ** Genus '' Leporinus''

Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he recei ...

, 1829 (71 species) ** Genus '' Megaleporinus'' Ramírez, Birindelli & Galetti, 2017 (10 species) ** Genus '' Rhytiodus'' Kner, 1858 (four species) ** Genus '' Schizodon'' Agassiz, 1829 (16 species) In Brazil, many species of '' Leporinus'', '' Rhytiodus'', and '' Schizodon'' are called aracu.

Evolution and fossil record

The

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

Anostominae is also used to denote the entire family in outdated treatments, where the name "Anostomidae" is applied to the entire Anostomoidea (and sometimes even more distant relatives). In that respect, agreement is widespread today that the closest living relatives of the Anostomidae ''

sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

'' are the Chilodidae headstanders, the toothless characins (Curimatidae) and the flannel-mouthed characins (Prochilodontidae). The origin of the Anostomidae can be quite confidently placed in the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

, and somewhat less securely in late Paleogene, based on various evidence. For one, the

biogeography Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities o ...

of the family, with some very basal taxa found west of the Andes, indicates it was already well distinct when the northern part of that mountain range uplifted at the end of the

Middle Miocene The Middle Miocene is a sub-epoch of the Miocene epoch (geology), epoch made up of two Stage (stratigraphy), stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0. ...

about 12

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

(Mya). Then, some scant but highly informative

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

evidence assigned to this family: a

ry tooth was found in the

n Villavieja Formation and dated to the

Laventan The Laventan () age is a period of geologic time (13.8 to 11.8 Ma) within the Middle Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Colloncuran and precedes the Mayoan age. ...

age about 13.5-11.5 Mya, while some

pharyngeal teeth Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species otherwise lacking teeth.jaw The jaws are a pair of opposable articulated structures at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth ...

parts found near

Cuenca, Ecuador Cuenca, officially Santa Ana de los Ríos de Cuenca, is an Ecuadorian city, head of the Cuenca Canton, canton of the same name and capital of the Azuay Province, province of Azuay, as well as its largest and most populated city. It is crossed by t ...

in the Cuenca basin (a

structural basin A structural basin is a large-scale structural geology, structural formation of rock stratum, strata formed by tectonics, tectonic warping (Fold (geology), folding) of previously flat-lying strata into a syncline fold. They are geological dep ...

) are about 19 million years old. The fossil remains resemble '' Leporinus'' and were assigned to the living genus, but given its paraphyly and rather basal position, until more fossils are found the known remains can only be considered fairly basal Anostomidae, ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'', but probably close to the ''Leporinus'' assemblage. The fossil ''Leporinus'' species '' Leporinus scalabrinii'', whose fossilized skull was previously thought to belong to a

primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...

, is known from the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

of Argentina.Bogan, S., Sidlauskas, B., Vari, R.P. & Agnolin, F. (2012)
''Arrhinolemur scalabrinii'' Ameghino, 1898, of the late Miocene - a taxonomic journey from the Mammalia to the Anostomidae (Ostariophysi: Characiformes).
'' Neotropical Ichthyology, 10 (3): 555–560.'''' Cyphocharax mosesi'', a fossil toothless characin found in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

, lived at the Oligocene-

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

boundary about 23 Mya. Thus, at that time, the Anostomoidea families must have already been well distinct by that point.Filleul & Maisey (2004), Sidlauskas & Vari (2008) Phylogenetic evidence suggests that the Anostomidae diverged from their closest relatives during the

Late Paleocene The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...

, about 59 million years ago, with the three subfamilies diverging from one another around the

Middle Eocene The Eocene ( ) is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''Ēṓs'', ' Dawn') a ...

(45 to 40 Mya).

Description

Systematics and evolution

Genera

Evolution and fossil record

References

Further reading