Taxonomy & naming
Scleropages inscriptus was formally described by the American ichthyologist Tyson R. Roberts in 2012, carved out of what had previously been treated as part of the wider "Asian arowana" complex, based on specimens traced to the Tenasserim (Tanintharyi) river basin of southern Myanmar. It sits in the family Osteoglossidae, the true bonytongues, within the order Osteoglossiformes — one of the most ancient living lineages of teleost (bony) fishes, whose members share the toothed tongue-bone, biting against a toothed roof of the mouth, that gives the order its name. The genus Scleropages is the true-arowana genus, also home to the Asian arowana (S. formosus) and the two Australian saratogas; S. inscriptus is currently placed alongside S. formosus in the subgenus Delsmania.
Roberts separated S. inscriptus from S. formosus and from the Australian species chiefly by a dense, maze-like pattern of markings covering the circumorbital bones around the eye, the opercular (gill-cover) bones, and the body scales — a feature distinctive enough that it is written into the species name itself: inscriptus is Latin for "inscribed" or "written upon." Because Myanmar-origin arowanas were long sold in the aquarium trade simply as "Asian arowana," specimens of S. inscriptus are still frequently mislabelled as S. formosus, a point both the Catalog of Fishes and the IUCN assessment flag explicitly.
Morphology
S. inscriptus has the classic true-arowana build: an elongated, laterally compressed, almost ribbon-like body; a large, strongly upturned mouth with a projecting lower jaw that opens like a drawbridge; and a pair of fleshy barbels on the chin used to detect prey at the surface. The body is covered in large, heavy, bony scales, and it is the intricate maze-like markings across these scales and across the bones around the eye and gill cover — rather than colour alone — that identify the species and give it its name. The type specimen measured 15.16 in, and the species is reported to reach a maximum of around 23.62 in (23.6 in) total length.
The dorsal and anal fins are set far back toward the tail, concentrating power at the rear of the body for the short, explosive bursts that a surface-ambush predator needs — both to seize fast prey and, famously in this genus, to launch clear of the water. Large, silvery-edged scales and a fully protrusible, upward-opening jaw complete a fish built to patrol just under the surface and strike upward.
Habitat
Scleropages inscriptus is endemic to the Tenasserim (Tanintharyi) river system of southern Myanmar in mainland Southeast Asia — a lowland freshwater basin far removed from the Amazon and from the Malay Peninsula strongholds of its relative S. formosus. FishBase classifies it as a freshwater, benthopelagic species, meaning it ranges through the water column over the riverbed rather than staying tight to the bottom or the surface alone.
Detailed water-chemistry data specific to this recently described species is sparse; as with other Southeast Asian Scleropages, it is reasonable to expect warm, soft, slightly acidic lowland river conditions typical of the region's forested watersheds, but published figures for wild S. inscriptus populations are not available.
Feeding
S. inscriptus is an obligate predator. In the aquarium literature it is fed bloodworms, earthworms, shrimp and whole fish — it does not take flake or algae-based foods and needs a meat-based diet throughout its life. Its upturned mouth and surface-oriented posture point to a predator that hunts near the top of the water column, taking fish, insects and other prey from the surface and, as true arowanas are known to do, from overhanging vegetation by leaping clear of the water.
Because it is a large, fast-growing carnivore, feeding in captivity has to scale with the fish: juveniles take smaller live and frozen foods, while adults need correspondingly larger prey items and a feeding regime built around a predator that can eventually exceed half a metre in length.
Mating
Specific observations of wild courtship and spawning in S. inscriptus have not been published — the species was only described in 2012 and remains poorly studied outside museum and trade material. Breeding biology in true arowanas (Scleropages) generally, including its close relative S. formosus, follows a paternal mouthbrooding pattern: eggs are large, few in number, and fertilised externally, after which the male takes the clutch into his mouth to incubate it.
Where documented in the genus, courtship involves a pair circling and positioning before the female releases a small number of large, yolky eggs that the male immediately gathers up rather than leaving to develop unattended on the substrate — a strategy suited to slow-flowing rivers where free-floating eggs would otherwise be highly vulnerable.
Breeding
As in other Scleropages, the male is expected to be a paternal mouthbrooder: after fertilisation he carries the large eggs in his mouth through incubation, and continues to shelter the free-swimming, yolk-sac-bearing fry there for a period afterward before they disperse. This is inferred from the well-documented biology of its close relative S. formosus rather than from direct observation of S. inscriptus, which — being both recently described and Data Deficient — has essentially no published breeding record of its own, wild or captive.
Parental investment in this mode is substantial for the small number of young produced: a mouthbrooding male forgoes feeding for an extended stretch while protecting the clutch, trading a large batch of small, unguarded eggs for a much smaller number of well-defended, well-developed offspring — the same trade-off that makes captive-bred Asian arowanas commercially viable, though no comparable captive-breeding programme is documented for S. inscriptus.
In the aquarium
This is not a beginner's fish, and Seriously Fish is blunt about it: given an adult size approaching 23.6 in and the athletic, jumpy temperament typical of true arowanas, S. inscriptus is realistically a fish for large public aquaria rather than home tanks. Any keeper taking one on needs a very heavy, tight-fitting lid — arowanas are powerful jumpers that will launch themselves at anything moving above the water line, and an unsecured tank all but guarantees an escaped or injured fish — plus a correspondingly enormous footprint of open swimming space, since the species patrols just under the surface rather than hovering in place.
As an obligate predator it needs a steady diet of appropriately sized meaty foods (see "Feeding") and strong filtration to handle the resulting bioload. Tankmates must be chosen with real caution: anything small enough to fit in that upturned mouth is at risk, while boisterous or fin-nipping fish can damage the arowana's own long fins and barbels. Buyers should also be aware that Myanmar-origin arowanas in the trade are frequently sold under the name S. formosus rather than correctly identified as S. inscriptus — a labelling problem noted by IUCN assessors, and a reminder that the species carries CITES Appendix I protection, a legal fact of its trade status rather than a recommendation either way.
Conservation
The IUCN Red List lists Scleropages inscriptus as Data Deficient, an assessment made in 2019 and reconfirmed in 2022 — there simply is not enough population data from its restricted Tenasserim range to judge trend or status with confidence. The species is protected under CITES Appendix I, the same strict international trade controls that apply to its relative the Asian arowana.
The IUCN assessment specifically notes that specimens traded internationally are often misidentified as S. formosus, which muddies any picture of real collection pressure on wild S. inscriptus populations — a taxonomically young, narrow-range species whose true conservation status remains, honestly, unknown.