The Ankylosaur isopod is sold as Reductoniscus tuberculatus, a tiny rolling woodlouse described in 1997 from Sabah, in Malaysian Borneo. It is about 5 mm long, covered in raised tubercles, and carries a hump on its seventh leg-bearing segment that gives it a tank-like outline. Keep it warm and steady at the 22 to 26°C on our listing's care panel, moderately humid with one damp end, on a fine, deep living substrate with leaf litter, rotted wood and calcium, and expect a burrower that you will see less often than a surface species.
The Species It Is Sold As
Leistikow named the species in 1997, in the Revue suisse de Zoologie, from three females collected in December 1995 at the War Memorial Park in Sandakan, Sabah. The largest, the holotype, measured 5 mm and the other two 2 to 3 mm. The paper describes no male and says nothing about how the animal lives, so every care figure you will see, ours included, comes from keepers and sellers.
It belongs to the family Armadillidae, and its genus is small: four described species, two of them from New Ireland, in Papua New Guinea. The genus has already turned up in Britain. Its type species, Reductoniscus costulatus, which reaches only about 2 mm, has been found in the tropical glasshouses at Kew and in the Eden Project's rainforest biome, presumably carried in by people.
Is the Trade Animal Really R. tuberculatus?
Every seller we read sells the Ankylosaur under that name, and most sellers' figures sit around Leistikow's 5 mm, though size alone cannot separate it from the look-alike below. We found no published examination of hobby stock by a specialist, so the name is the trade's identification rather than a confirmed one. It is not R. costulatus, which is sold separately and is far smaller. The name it does get muddled with is Tuberillo borneanus, another small, tubercled, rolling woodlouse from Sabah, described in 2010 and sometimes spelt "Turbellio borneonus" in listings. Hobby sources disagree about which name belongs on which animal, which is one more reason to treat any trade identification as provisional.
Ankylosaur, Dwarf Gator or Borneo Gator?
One hobby reference site likens the seventh leg-bearing segment, which arches back over the tail, to the clubbed tail of an ankylosaur, and Leistikow found the hump on that segment most conspicuous in this species. In North America several sellers list the same animal as the Dwarf Gator, the Borneo Gator or the Borneo Alligator, though at least one American seller also calls its Thai gators dwarf gator species, so if you meet a Dwarf Gator, check the scientific name. It is not the Shiny Gator, an undescribed animal sold as Thai. Nor is it the larger pill woodlouse from the Aegean islands that shares its species name, covered in our Armadillo tuberculatus care guide.
Size and Appearance
Leistikow gave "a maximum length of 5 mm" for his three animals, the length of the largest, and we found no later measurement; the 5 mm on our care panel is that figure. Sellers' figures run from about 4 mm up to one seller's 6 to 8 mm, which is larger than any measurement we found. Leistikow described his specimens as buff to rosy cream, without saying whether that was their colour in life. In the photographs on our listing the live animals run from white to a pale blue-grey, with the tubercles paler than the shell between them.
Rolling Up and Burrowing
The whole genus can roll into a tight ball, and Leistikow's description notes the grooves the antennae fold into when it does. Most keepers and sellers describe the Ankylosaur as a burrower, though one seller finds it active. Expect to see it less than a surface species, and look for it under bark and in the top of the substrate rather than out on the leaf litter.
Warmth
Our care panel gives 22 to 26°C, which matches one UK seller exactly. Other sellers give 18 to 26°C and 21 to 27°C, and one keeper keeps them at 24 to 27°C. Aim for steady warmth inside the band rather than the top of it. An English home averages about 19°C through the heating season, so use a heat mat or heat cable on a thermostat, fixed to the side of the tub, never underneath, through the colder months at least.
Humidity and Air
We found no scientific figure for humidity. Sellers describe it as anything from medium to consistently high, and the only percentage we found, 75 to 85, came from one American seller. The 60 to 70 per cent on our care panel is our own figure, not a published one, and it describes the whole tub: the drier end near 60, the damp end, under moss, near 70. Never let the substrate dry right through, and if the colony spends all its time in the damp end, let that end run wetter. Give gentle airflow from a few small vents with fine mesh over them, because the young are small enough to slip through anything wider.
Substrate, Cover and Calcium
Give it depth. The sellers who mention substrate ask for it deep and moisture-holding, and a burrowing species uses every centimetre. Aim for at least 5 to 8 cm of flake soil, white-rotted hardwood and organic topsoil, with crushed limestone or crushed oyster shell mixed through it; our piece on topsoil for isopod substrate covers the soil part of the mix. Add a layer of leaf litter and flat bark on top. One seller says leaves are not needed, but most recommend them, and they are food as well as cover. Leave coir out: it holds water and feeds nothing to an animal that eats its substrate.
Feeding
The Ankylosaur is a detritivore, and decaying hardwood and leaf litter make up its diet. Sellers add a little fish food for protein. Give protein in small pinches once or twice a week, clear uneaten food after a day or two, and keep a calcium source in the tub all the time. Woodlice build their cuticle from calcium carbonate, so calcium goes in every isopod tub, this one included.
Breeding
We found no published brood size, time to maturity or breeding pace. The holotype was not carrying young, and sellers' accounts run from slow to steady. Start with as many as you can, at least 20 where possible and no fewer than 10: most woodlice need both sexes to breed, and since we found no description of a male for this species, a larger group gives you the best chance of having both. The young are extremely small, so work in the tub gently and as little as possible while a group settles, and judge it after a season.
Who It Suits
Sellers rate it anywhere from beginner to intermediate, and our care panel says Medium. It is a collector's animal, for someone who wants the textured end of the hobby and is happy to keep a species they will not see every day, rather than a working colony for a vivarium. For a first dwarf, the Dwarf White is the easier start, and our spiky isopods piece shows where the Ankylosaur sits among the other textured species.
Frequently Asked Questions
What is an Ankylosaur isopod?
A tiny, tubercled rolling woodlouse sold as Reductoniscus tuberculatus, a species described in 1997 from Sabah, in Malaysian Borneo.
How big do Ankylosaur isopods get?
About 5 mm. The species was described from three females, one of 5 mm and two of 2 to 3 mm, and we found no later measurement; one seller gives 6 to 8 mm.
Where do Ankylosaur isopods come from?
The species was described from Sandakan, in Sabah. Sellers list it as Bornean, but we found no published collecting site for hobby stock.
Is the Ankylosaur the same as the Dwarf Gator?
Usually. Several North American sellers list it as the Dwarf Gator, the Borneo Gator or the Borneo Alligator, but at least one uses dwarf gator for Thai gators too, so check the scientific name. Either way, the Ankylosaur is not the Shiny Gator.
Do Ankylosaur isopods roll up?
Yes. The whole genus rolls into a tight ball when disturbed.
Are Ankylosaur isopods easy to keep?
Their care is not unusual, but they are small, secretive and slow to judge, so our care panel rates them Medium rather than Easy.
Where to Start
The Ankylosaurs we sell are captive-bred, and the Ankylosaur listing shows the packs in stock and carries the care panel this guide quotes.
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