Plecostomus Gronovius 1754
Cochliodon Heckel 1854
Cheiridodus Eigenmann 1922
Isorineloricaria Isbrücker 1980
Aphanotorulus Isbrücker & Nijssen 1982
Squaliforma Isbrücker & Michels 2001
Watawata Isbrücker & Michels 2001

SPECIES (types examined)

H. affinis (Steindachner 1877)
H. agna (Miranda Ribeiro 1907)
H. alatus Castelnau 1855
H. albopunctatus (Regan 1908)
H. ammophilus (Armbruster & Page 1996)
H, ancistroides (Ihering 1911)
H. angipinnatus (Leege 1922)
H. annae (Steindachner 1881)
H. argus (Fowler 1943)
H. asperatus Castelnau 1855
H. aspilogaster (Cope 1894)
H. atropinnis (Eigenmann & Eigenmann 1890)
H. auroguttatus Kner 1854
H. bicirrosus (Gronow 1854) (Synonym of H. plecostomus)
H. biseriatus (Cope 1872)
H. bolivianus (Pearson 1924)
H. borellii (Boulenger 1897)
H. boulengeri (Eigenmann & Kennedy 1903)
H. brasiliensis (Bleeker 1863) (Synonym of H. plecostomus)
H. brevicauda (Günther 1864)
H. brevis (Nichols 1919)
H. butantanis (Ihering 1911) (Synonym of H. margaritifer)
H. carinatus (Steindachner 1882)
H. carvalhoi (Ribeiro 1937)
H. chaparae (Fowler 1940) (Synonym of H. unicolor)
H. cochliodon Kner 1854
H. commersoni Valenciennes 1836
H. commersonoides (Marini, Nichols and La Monte 1933) (Synonym of H. laplatae)
H. coppenamensis Boeseman 1969
H. corantijni Boeseman 1968
H. cordovae (Günther 1880)
H. crassicauda Boeseman 1968
H. derbyi (Haseman 1911)
H. dlouhyi Weber 1985
H. emarginatus Valenciennes 1840
H. eptingi (Fowler 1941)
H. ericae Carvalho and Weber 2005
H. ericius Armbruster 2003
H. festae (Boulenger 1898) (Synonym of H. spinosissimus)
H. flava (Shaw 1804) (Synonym of H. plecostomus)
H. fluviatilis (Schubart 1964)
H. fonchii Weber and Montoya-Burgos 2002
H. francisci (Lütken 1874)
H. frankei (Isbrücker & Nijssen 1982) (Synonym of H. ammophilus)
H. garmani (Regan 1904)
H. gomesi (Fowler 1942)
H. goyazensis (Regan 1908)
H. guacari Lacepède 1803 (Synonym of H. plecostomus)
H. gymnorhynchus (Norman 1926)
H. hemicochliodon Armbruster 2003
H. hemiurus (Eigenmann 1912)
H. hermanni (Ihering 1905)
H. hondae (Regan 1912)
H. hoplonites Rapp Py-Daniel 1988
H. horridus Kner 1854
H. iheringi (Fowler 1941) (Synonym of H. gomesi)
H. iheringii (Regan 1908)
H. interruptus (Miranda Ribeiro 1918)
H. isbrueckeri Reis, Weber, and Malabarba 1990
H. itacua Valenciennes 1836
H. jaguribensis (Fowler 1915)
H. johnii (Steindachner 1877)
H. laplatae (Eigenmann 1907)
H. latifrons Weber 1986
H. latirostris (Regan 1904)
H. levis (Pearson 1924)
H. lexi (Ihering 1911)
H. lima (Lütken 1874)
H. limosus (Eigenmann & Eigenmann 1888) (Synonym of H. commersoni)
H. longiradiatus (Holly 1929)
H. luetkeni (Steindachner 1877) (Synonym of H. auroguttatus)
H. luteomaculatus (Devicenzi 1942)
H. luteus (Godoy 1980)
H. macrophthalmus Boeseman 1968
H. macrops (Eignemann & Eigenmann 1888)
H. macushi Armbruster and de Souza 2005
H. madeirae (Fowler 1913) (Synonym of H. unicolor)
H. margaritifer (Regan 1908)
H. meleagris (Marini, Nichols and La Monte 1933)
H. micromaculatus Boeseman 1968
H. micropunctatus (La Monte 1935) (Synonym of H. unicolor)
H. microstomus Weber 1987
H. mutucae Knaack 1999
H. myersi (Gosline 1947)
H. nematopterus Isbrücker & Nijssen 1984
H. niceforoi (Fowler 1943)
H. nickeriensis Boeseman 1969
H. niger (Marini, Nichols and La Monte 1933)
H. nigromaculatus (Schubart 1964)
H. nudiventris (Fowler 1941)
H. obtusirostris (Steindachner 1907)
H. occidentalis Boeseman 1968
H. oculeus (Fowler 1943)
H. pagei Armbruster 2003
H. pantherinus Kner 1854
H. papariae (Fowler 1941)
H. paranensis Weyenberg 1877 (Synonym of H. cordovae)
H. paucimaculatus Boeseman 1968
H. paucipunctatus Carvalho and Weber 2005
H. paulinus (Ihering 1905)
H. phrixosoma (Fowler 1940)
H. piratatu Weber 1986
H. plecostomoides (Eigenmann 1922)
H. plecostomus (Linnaeus 1758)
H. popoi (Pearson 1924) (Synonym of H. unicolor)
H. pospisili (Schultz 1944) (Synonym of H. hondae)
H. pseudohemiurus Boeseman 1968
H. punctatus Valenciennes 1840
H. pusarum (Starks 1913)
H. pyrineusi (Ribeiro 1920)
H. rachovii (Regan 1913) (Synonym of H. laplatae)
H. regani (Ihering 1905)
H. robinii Valenciennes 1840
H. rondoni (Ribeiro 1912)
H. roseopunctatus Reis, Weber and Malabarba 1990
H. salgadae (Fowler 1941)
H. saramaccensis Boeseman 1968
H. scabriceps (Eigenmann and Eigenmann 1888)
H. scaphyceps (Nichols 1919)
H. scopularius (Cope 1871)
H. sculpodon Armbruster 2003
H. seminudus (Eigenmann and Eigenmann 1888)
H. simios Carvalho and Weber 2005
H. sipaliwinii Boeseman 1968
H. soniae Carvalho and Weber 2005
H. spiniger (Hensel 1870) (Synonym of H. commersoni)
H. spinosissimus (Steindachner 1880)
H. squalinus Jardine and Schomburgk 1841
H. strigaticeps (Regan 1908)
H. subcarinatus Castelnau 1855
H. surinamemsis Boeseman 1968
H. taeniatus (Regan 1908) (Synonym of H. laplatae)
H. tapanhoniensis Boeseman 1969
H. taphorni (Lilyestrom 1984)
H. tapijara Oyakawa, Akama, and Zanata 2005
H. tenuicauda (Steindachner 1878)
H. tenuis Boeseman 1968
H. ternetzi (Boulenger 1895)
H. tietensis (Ihering 1905)
H. topavae (Godoy 1969)
H. unae (Steindachner 1878)
H. unicolor (Steindachner 1908)
H. uruguayensis Reis, Weber, and Malabarba 1990
H. vaillanti (Steindachner 1877)
H. variipictus (Ihering 1911)
H. varimaculosus (Fowler 1945)
H. variostictus (Miranda Ribeiro 1912)
H. ventromaculatus Boeseman 1968
H. vermicularis (Eigenmann and Eigenmann 1888)
H. verres Valenciennes 1840 (synonym of H. watwata)
H. villarsi (Lütken 1874)
H. virescens Cope 1874
H. waiampi Carvalho and Weber 2005
H. watwata Hancock 1828
H. winzi (Fowler 1945)
H. wuchereri (Günther 1864)

Hypostomus is not diagnosed by any unique characteristics. Characteristics considered synapomorphic for the group are: a hatchet-shaped opercle, the anterior process of the pterotic-supracleithrum passing halfway through the orbit, and a pointed cleithral process. In addition, in several trees, the bulk of Hypostomus (except H. commersoni Valenciennes and H. boulengeri [Eigenmann and Kennedy]) are supported by a pointed transverse process of the Weberian apparatus that is fused to the pterotic-supracleithrum.

Small to large loricariids that defy a unifying description. Color pattern varies from having a white ground color and black spots, to brown and spotted, to black with red, gold, or white spots. Abdomen also varies in color from white to black and may be spotted or not. Abdomen ranges from naked to completely plated (usually with plates). Caudal fin forked with the lower lobe longer than upper. Two or three predorsal plates. Five rows of plates on caudal peduncle (except H. dlouhyi  Weber which has three). Hypostomus emarginatus group, H. cordovae(Günther), and H. spiniger (Hensel) with elongated bodies with H. spinossimus most elongate with a very long, whiplike tail that is circular in cross-section in adults. Most other species have stout bodies. Lateral plates keeled or not. Cheek plates evertible to approximately a 30° angle.

SEXUAL DIMORPHISM.—In most, males develop hypertrophied odontodes on the leading edge of the pectoral-fin spine and the distal tip of the spine may become swollen. Additionally, in members of the H. emarginatus clade, males develop hypertrophied odontodes on the body during the breeding season (Armbruster & Page, 1996); these odontodes are normally best developed on the posterolateral plates, the caudal-fin spines, and the adipose-fin spine. In addition, H. spinosissimus develops hypertrophied odontodes over the entire lateral and dorsal surface of the body including the cheeks (the cheek plates are not highly evertible). Nuptial males of H. ammophilus and H. unicolor develop elongate, unicuspid teeth (Armbruster & Page, 1996). Nuptial males of some species of the H. cochliodon group develop wider, more widely spaced odontodes on the lateral plates (the odontodes are not longer in nuptial males, VIEW-B).

Hypostomus is most similar to the Hemiancistrus annectens group. Externally, Hypostomus is very difficult to separate from the Hemiancistrus annectens group differing mainly in the lack of highly evertible cheek plates with hypertrophied odontodes in adults (cheek odontodes are present in H. spinosissimus, but they are present only in nuptial males, are not highly evertible, and are accompanied by a lengthening of nearly all of the odontodes on the body) and by usually having only one (occasionally two) row of plates between the suprapreopercle and the exposed opercle (vs. three, occasionally two). The only species of Hypostomus sympatric or potentially sympatric with the Hemiancistrus annectens group are members of the the H. cochliodon group which have wide, spoon-shaped teeth (vs. viliform teeth, VIEW A vs B and C) and H. spinosissimus, H. tenuicauda and H. villarsi which have a white or tan ground color (versus dark brown) and are elongate (vs. short); thus, most Hypostomus can be separated from the Hemiancistrus annectens group by having a distribution east of the Andes (vs. west). Hypostomus can be distinguished from most Pterygoplichthys by the same characters as for the Hemiancistrus annectens group with the addition of having only 7 (vs. 9-14) dorsal-fin rays; from all but Pseudorinelepis of the the Rhinelepis group by having a single, medium-sized plate posterior to the pterotic-supracleithrum (vs. many small plates); from all but Pogonopoma of the the Rhinelepis group  by usually having an adipose fin (adipose fin is also missing in C. levis); from all the Rhinelepis group by having one unbranched and four branched anal-fin rays (vs. one unbranched and five branched rays) and a dorsal flap of the iris making the eye appear bilobed (vs. iris round, without flap); and from most of the Ancistrini by a lack of highly evertible cheek plates with hypertrophied odontodes (Spectracanthicus lacks evertible cheek plates with hypertrophied odontodes and can be distinguished by having the dorsal-fin membrane attached to the preadipose plate; some Pseudancistrus lack evertible cheek plates and can be distinguished by a combination of the presence of hypertrophied odontodes along the snout and on the cheek and no plates on the abdomen).

Hypostomus is essentially ubiquitous across their range. Most species are lowland, sluggish stream- and lake-dwellers usually found associated with submerged wood; however, many species may be found among rocks in piedmont to mountain streams with moderate to swift flow. Members of Hypostomus may be found over substrates ranging from mud and detritus, to gravel and cobble and boulders, to sand. Many spawn in hollows dug into mud banks or within hollow logs (Burgess; 1989).

Throughout most of the range of loricariids except for drainages west of the Río Atrato.

Armbruster, J.W. 1997. Phylogenetic relationships of the sucker-mouth armored catfishes (Loricariidae) with particular emphasis on the Ancistrinae, Hypostominae, and Neoplecostominae. Unpubl. Ph.D. dissertation. University of Illinois, Urbana-Champaign. 409 pp.

Armbruster, J. W. 2004. Phylogenetic relationships of the suckermouth armoured catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae. Zoological Journal of the Linnean Society 141:1-80.

Armbruster, J.W. and L.M. Page. 1996. Redescription of Aphanotorulus (Teleostei: Loricariidae) with description of one new species, A. ammophilus, from the Río Orinoco basin. Copeia 1996:379-389.

Burgess, W.E., 1989. An atlas of freshwater and marine catfishes, a preliminary survey of the Siluriformes. T.F.H. Publications, Neptune City, New Jersey. 784 pp.