Taxonomy & naming
Paratrygon raonii was described by Loboda in 2026, in the same Neotropical Ichthyology paper that simultaneously named three sibling species from the Tocantins, Araguaia and Tapajós rivers, raising the genus Paratrygon from three previously recognized species to seven. It is placed in family Potamotrygonidae, subfamily Potamotrygoninae, order Myliobatiformes.
The holotype, MZUSP 104444, is an adult male of 21.93 in disc width, collected from the rio Xingu at the Municipality of São Félix do Xingu, Pará State, Brazil (06°39'23.33"S, 51°59'56.72"W) in July 2005. Earlier molecular studies (Frederico et al., 2012; Fontenelle et al., 2021; Sanches et al., 2021, using COI and cytochrome b sequences on Xingu-basin material) had already identified this lineage as genetically distinct from typical P. aiereba downstream in the same river; the 2026 description formalizes it using coloration, spiracle shape, dermal-denticle morphology and skeletal characters. Catalog of Fishes (Eschmeyer, CAS) is the authority for the valid name used here. The species is named for Raoni Metuktire, a Kayapo Indigenous leader, environmentalist and activist who has spent decades campaigning to protect the rio Xingu, its Indigenous peoples and the surrounding Amazon rainforest — an honor the paper states explicitly.
Morphology
Paratrygon raonii is the largest of the four newly described clear-water Paratrygon species. The holotype adult male measured 21.93 in disc width, and adult specimens examined in the description averaged 24.75 in and reached 34.37 in disc width (roughly 24.8–34.3 in) — the second-highest mean total length recorded in the genus, at 32.03 in average and 37.72 in maximum, with the highest mean and maximum disc length of any Paratrygon species measured to date.
The dorsal disc is gray, dark gray, light brown, brown, dark brown or black, marked with dark, thread-like or branching (vermiculated) spots that are notably evident against the ground color, with pale rounded spots present in some individuals — a darker, more strongly marked pattern than in P. araguaia or P. lucindai. The spiracles are very small, roughly the size of the eye or only slightly larger, quadrangular, with a pronounced spiracular process — the smallest mean spiracle length recorded in the genus (4% disc width). P. raonii also has the narrowest branchial basket and, unusually for the genus, a longer caudal sting than its relatives. As in the rest of Paratrygon, the tail carries a serrated venomous spine near its base.
Habitat
Paratrygon raonii is documented from the middle portion of the rio Xingu, in Pará State, Brazil, and the describing authors consider it likely to extend into the upper river as well. The Xingu is one of the Amazon basin's major clear-water rivers, rising from the weathered Precambrian soils of the Brazilian Crystalline Shield; such rivers run relatively transparent, olive-green in color, slightly acidic (roughly pH 6.0–6.8) and carry very low sediment and mineral loads, in sharp chemical contrast to the muddy, whitewater channels of the central Solimões-Amazonas system where the widespread P. aiereba lives.
The describing authors propose that this basin-scale contrast in water chemistry between clear-water and white-water systems is itself a plausible driver of diversification within the genus, noting that P. raonii and P. araguaia — from the geologically related Xingu and Tocantins-Araguaia systems — appear to share a closer historical relationship with each other than either does with P. munduruku of the Tapajós. Like the rest of its family, P. raonii is benthic, breathing through the spiracles on top of its head while resting on the riverbed.
Feeding
No dietary data specific to Paratrygon raonii has been published; its 2026 description is a taxonomic and morphological revision of preserved museum specimens rather than a feeding study. What is known draws on biology shared across Potamotrygonidae: these are benthic ambush predators that locate hidden prey using the ampullae of Lorenzini, an electro-sensory system concentrated on the ventral disc.
Across the family the diet centers on aquatic insect larvae, crustaceans, molluscs and worms, supplemented opportunistically with small fishes, pinned beneath the disc and worked to the crushing tooth plates of the ventral mouth. Given its large adult size, P. raonii likely takes correspondingly larger prey than its smaller congeners, though this remains an inference rather than a documented observation.
Mating
As in all elasmobranchs, fertilization in Paratrygon raonii is internal: a male grips a female's disc, typically biting at the margin, and inserts one of his paired claspers to transfer sperm. No courtship or mating behaviour specific to this species has been observed or published — the 2026 description draws on preserved specimens rather than field or captive observation.
This reproductive mode is uniform across Potamotrygonidae, so it can be attributed to P. raonii with confidence even without direct observation, though the specifics of its courtship remain undocumented.
Breeding
Paratrygon raonii is presumed viviparous, in keeping with the whole family, nourishing developing pups after the yolk is exhausted through matrotrophic histotrophy — a nutrient-rich uterine secretion the embryos absorb directly. This mode is documented broadly across Potamotrygonidae; no litter size or gestation length specific to P. raonii has been published.
Given that this is the largest of the newly described Paratrygon species, with adult disc widths averaging nearly 24.8 in and reaching 34.3 in, a small-litter, long-gestation strategy broadly similar to that documented for the type species P. aiereba would be expected on genus-level grounds, though this remains inferred rather than directly observed for P. raonii.
In the aquarium
Paratrygon raonii is not an aquarium fish. It was described only in 2026 from museum material, and Paratrygon as a genus consists of exceptionally large "discus rays" whose adult disc widths run from roughly 19.7 in to nearly 35.4 in or more — a scale, confirmed for this species by its own adult measurements, that places it well beyond any home aquarium and squarely into the domain of large public displays and dedicated research collections.
Were specimens ever to reach the trade, the husbandry requirements would be extreme: many square metres of floor space, a deep bed of soft, fine sand for a species with a long, delicate tail, warm and carefully controlled water chemistry, and total avoidance of copper-based medications. The serrated venomous spine is a genuine medical hazard. Given the species' apparent single-river endemism and its status as a 2026 description, there is no responsible case for collecting it for the aquarium trade.
Conservation
Paratrygon raonii has not been formally assessed by the IUCN Red List; as a species named in 2026 it currently carries no Red List status. The describing authors, applying IUCN criteria informally within their taxonomic paper, suggested a category of Data Deficient, noting that while the species appears widespread through the middle Xingu and its tributaries with no imminent threats currently identified, further study of its population status is needed. This is the describing authors' own proposed assessment, not an official Red List determination.
The authors flagged the four newly described clear-water Paratrygon species collectively, including P. raonii, as possibly the most vulnerable in the genus because of their endemism to single river systems in a region under mounting anthropogenic pressure. The middle Xingu in particular sits downstream of major hydroelectric development on the river, making continued population monitoring and a formal Red List assessment priorities for this species.