Aquarium ‘plecos’ are Earth’s largest catfish family
Loricariidae holds more than ninety genera and just over 680 species—the biggest catfish family on the planet. Armoured in bony plates and fitted with suckermouths, they range from Costa Rica and Panama through tropical and subtropical South America. Hobbyists still call many of them “plecos,” a nickname borrowed from one early import.
Cascudos or acarís at home, suckermouth armoured catfishes in English lists, these siluriforms are so morphologically specialised that even early classifiers treated them as a natural group. They sit in superfamily Loricarioidea beside relatives that may show either a suckermouth or armour—but almost never both on one fish, as loricariids do. Hypostomus plecostomus was among the first species shipped for aquaria, so “plecostomus,” “pleco,” and “plec” stuck to many lookalikes, though slender Farlowella types are usually exempted from the nickname.
Taxonomy stays restless: roughly 684 species in about ninety-two genera, with descriptions still arriving yearly. Under Jonathan Armbruster’s framework, recognised subfamilies include Delturinae, Hypoptopomatinae, Hypostominae, Lithogeneinae, Loricariinae, and Neoplecostominae; Hypostominae alone sprawls across five tribes, Ancistrini the largest. Lithogenes is the most basal living branch—sister to the rest—though its exact placement has been debated. Monophyly of some other subfamilies remains under review.
Importers once received undescribed South American fish tagged only with “L-numbers,” a stopgap code aquarists and biologists still use until formal names land—sometimes one L-number hid several species, sometimes two codes marked one. Fossils are scarce; the earliest secure loricariid is Taubateia from Brazil’s Late Oligocene–Early Miocene. A 2024 claim that Cenomanian Afrocascudo was an early loricariid remains disputed, with some arguing it may be a juvenile gar relative instead. Defenders of Afrocascudo point to its fully ossified bones, a sign of adulthood, and to missing holostean traits. Within Loricarioidea, jaw complexity climbs toward loricariids, which carry the most advanced jaws of all, and that trend may explain their extraordinary diversification.
Common names attached to the subfamilies hint at their looks: Lithogeninae are the climbing armored catfishes, Delturinae the primitive suckermouths, Loricariinae the mailed catfishes, and Hypoptopomatinae go by cascudinhos. Rank itself shifts over time. Nelson's Fishes of the World still listed Ancistrinae as a subfamily in its 2006 edition, but it was later demoted to a tribe once it proved to be the sister group of Pterygoplichthyini; its 30 genera now outnumber the roughly 24 shared by the other four Hypostominae tribes. Neoplecostominae, the next-most basal group after Lithogenes, may not form a natural grouping at all.
Source: Loricariidae
