Anostomidae

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Anostomidae
Abramites hypselonotus in
headstander swimming pose
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Suborder:
Characoidei
Family: Anostomidae
Günther, 1864[1]
Genera

Presently 14, but see text

Synonyms

Anostomina Günther, 1864
Anostominae (sensu Boulenger, 1904 et al.)

The Anostomidae are a

scientific name approximately means "mouth on top", from Ancient Greek áno- (ἄνω) "up" (as an adverb) + stóma (στόμᾶ) "mouth", in reference to the arrangement of these fishes' mouth opening.[2]

Description

Anostomids have elongated bodies ranging from 15 to 60 cm (5.9 to 23.6 in) in length; their shape varies between

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 plants near the bottom, while others also eat detritus and invertebrates picked up from river- or lakebeds. Adults guard the eggs after spawning. Anostomidae are generally considered edible, and some of the larger species are caught for food on a regular basis, much like large Leuciscinae (which are superficially similar Cypriniformes) are in the temperate Northern Hemisphere.[3]

Their jaws are rather short, with the maxillary bone small and excluded from the mouth opening, while the ascending process of the premaxilla 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 are enlarged and have two or more cusps each.[3]

Anostomid

circumorbital bone series is complete and includes a supraorbital bone, and at least four, often more, of the forward ribs are united by two or more intercostal ligaments.[2]

The

rays, respectively.[2]

Systematics and evolution

Black-banded Leporinus (Leporinus fasciatus), the type species of Leporinus

This family is in all probability

monotypic subfamily by some. A large clade of "modern" genera was treated as Anostominae by some authors; others considered that subfamily more inclusive.[1]

But the latter view is incorrect, as it includes a large number of lineages that are really

sensu lato clade could warrant recognition as another subfamily. Finally, Rhytiodus and Schizodon would almost certainly qualify as another subfamily, even if only the Anostominae warrant recognition otherwise.[1]

Evolution and fossil record

The

flannel-mouthed characins (Prochilodontidae).[1]

The origin of the Anostomidae can be quite confidently placed in the

Villavieja Formation[4] and dated to the Laventan age about 13.5-11.5 Mya, while some pharyngeal teeth and other jaw parts found near Cuenca, Ecuador in the Cuenca basin (a structural basin[5]) 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, but probably close to the Leporinus assemblage.[1]

molecular phylogenetic studies.[6]

Genera

The genera of Anostomidae are:[1]

Basal lineages

Schizodon clade

Anostominae sensu stricto

In Brazil, many species of Leporinus, Rhytiodus, and Schizodon are called aracu.[8]

References

  1. ^ a b c d e f Sidlauskas & Vari (2008)
  2. ^ a b c FishBase (2004), Sidlauskas & Vari (2008)
  3. ^ a b Weitzman & Vari (1998), FishBase (2004), Sidlauskas & Vari (2008)
  4. ^ "La Venta formation" in Sidlauskas & Vari (2008) is the old name.
  5. hdl:20.500.11850/143222
    .
  6. ^ Filleul & Maisey (2004), Sidlauskas & Vari (2008)
  7. ^ Ramirez, J.L., Birindelli, J.L.O. & Galetti, P.M.Jr. (2017): A new genus of Anostomidae (Ostariophysi: Characiformes): Diversity, phylogeny and biogeography based on cytogenetic, molecular and morphological data. Molecular Phylogenetics and Evolution, 107: 308–323.
  8. ^ Aracus. www.amazonwaters.org.

Further reading

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