Taxonomy & naming
Myloplus taphorni was described in 2019 by Marcelo Andrade, Hernán López-Fernández and Devya Liverpool from specimens collected in the middle Mazaruni River, a black-water tributary within the Essequibo basin of Guyana. It belongs to Serrasalmidae — the piranhas, pacus and silver dollars — within Characiformes, and to the genus Myloplus, one of several silver-dollar lineages that the Catalog of Fishes (Eschmeyer, California Academy of Sciences) now recognises as split out of the old, broadly defined genus Myleus. The original description also revisited the taxonomic status of Myleus pacu in light of the new species, part of the ongoing untangling of Serrasalmidae genera that has moved many silver dollars from Myleus into Myloplus, Tometes and Ossubtus.
The species epithet honours the American ichthyologist Donald C. Taphorn, recognising his extensive work on Neotropical freshwater fishes. The type series comprises a holotype of 5.5 in standard length plus paratype material ranging 5.5–6 in SL, all collected from the same black-water river system, which remains the only confirmed locality for the species.
Morphology
Myloplus taphorni has the classic silver dollar build: a deep, strongly laterally compressed, disc-shaped body with a small head and a mouth set with close-packed, molariform teeth adapted for grinding plant material rather than cutting flesh. Among its Myloplus relatives, which range roughly 6.5–22 in depending on species, M. taphorni is one of the smaller members of the genus, with the type series topping out at 6 in SL (roughly 6 in) and a practical adult size usually cited around 5.5–6 in.
The original description notes clear sexual dimorphism in colour and fin shape. Males show a purplish-silver body with black overtones and a metallic green sheen, and — as in several Myloplus species — elongated middle rays on the anal fin that form a distinct lobe. Females are a plainer bluish-silver without the elongated anal-fin lobe. As with other silver dollars, the flattened, mirror-bright body plan is built for moving efficiently in loose schools through open water rather than for solitary ambush.
Habitat
The species is currently known only from black-water channels of the middle Mazaruni River, part of the Essequibo River basin in Guyana. Collection data from the type description put it in genuine black water: warm (80–84 °F) and strongly acidic (pH around 5.1), with extremely low conductivity of only 4–12 µS/m — water so mineral-poor it barely conducts electricity, a hallmark of the tannin-stained rivers draining the Guiana Shield's ancient, weathered soils.
Within those channels the type specimens were taken around rocky and woody debris substrate at depths of a metre or more, consistent with a fish that shelters among submerged structure while schooling in open water to feed. No other river system has yet been documented for the species, so its range should be treated as narrow and specific to this one black-water drainage until further survey work says otherwise.
Feeding
Myloplus taphorni is herbivorous, in keeping with the molariform dentition described in the original type description and with the diet documented across Myloplus and related silver dollar genera: aquatic vegetation, algae, and likely fallen fruit, seeds and plant debris from the flooded forest margin, a food source shared by many Serrasalmidae in Guiana Shield black-water systems. The grinding tooth plates are built for macerating tough plant tissue rather than for seizing prey.
No aquarium feeding data exists for this species specifically, as it is not established in the hobby. Based on its genus and its dentition, a keeper attempting to maintain it should expect a committed plant-eater requiring vegetable-forward foods — blanched greens, spirulina and algae-based wafers — with any protein offered only as a minor supplement, exactly as with better-known Myloplus and Metynnis silver dollars.
Mating
Nothing specific to Myloplus taphorni has been documented about courtship or pairing behaviour; the species was described from preserved type material collected in the wild, not from observed breeding. What is documented is sexual dimorphism useful for identifying ripe or breeding-condition fish: males show the deeper purplish-silver colouration with a metallic green sheen and the elongated middle anal-fin rays forming a lobe, while females are a plainer bluish-silver and lack the lobed fin. This dimorphism, present in preserved specimens of both sexes in the type series, is the only sex-linked signal currently on record.
Breeding
There is no aquarium or field breeding record for Myloplus taphorni — it has not been kept or bred in the hobby, and no spawning observations exist in the scientific literature reviewed here. By analogy with its genus, silver dollars including Myloplus species are egg-scatterers that release eggs over fine-leaved plants with no nest construction and no parental care afterward; this is the general pattern for the group, not a confirmed observation for this particular species, and should be understood as inference rather than documented fact for M. taphorni specifically. Given its narrow known range and complete absence from the trade, breeding data may remain sparse for the foreseeable future.
In the aquarium
Myloplus taphorni is not established in the aquarium hobby — it was described only in 2019 from a single Guyanese black-water river, and no SeriouslyFish profile, care guide or hobbyist account of the species could be located. Any care plan is therefore extrapolated from its genus and its documented biology, not from direct experience with the species.
As a silver dollar, it should be expected to need a real school (a handful of individuals at minimum) in a spacious, open-swimming tank, and — like its Myloplus and Metynnis relatives — to be a committed grazer that will shred soft aquarium plants rather than coexist peacefully with a planted aquascape. Its documented native water is warm (roughly 81–84 °F), very soft and strongly acidic (pH around 5.1), conditions considerably more extreme than the generalist middle ground many aquarium silver dollars tolerate, so a keeper attempting this species should not assume it will thrive in ordinary tap-water conditions without acidification. At an adult size around 5.5–6 in it stays smaller than many Serrasalmidae, but it should still be housed in a robust, hard-scaped setup built to handle plant loss and a schooling fish's need for swimming space, not a delicate aquascape.
Conservation
Myloplus taphorni has not been assessed by the IUCN Red List; as a species described only in 2019 and currently known from a single black-water river system in Guyana, it is best treated as data-deficient rather than assumed safe. Its narrow known range in the middle Mazaruni River means that any localised pressure — mining, deforestation or water-quality change within the Essequibo basin's Guiana Shield headwaters, an area facing increasing gold-mining pressure across the region — could disproportionately affect the only documented population. No aquarium trade demand has been recorded for the species, so collection pressure is presumed minimal, but its restricted distribution alone is a reason for caution until a proper population assessment exists.