Smaller individuals of this species are like walking pin cushions. The broad, oval carapace (to 23 cm) is flattened dorsally, but has a medial keel. A spinelike projection occurs on the keel at the posterior border of each vertebral. There is also a small spine located near the posterior margin of each pleural scute. Many of these spines become worn down and are lost with age, so that larger individuals are much smoother than juveniles. Anterior and posterior marginals are also somewhat upturned. All vertebrals are broader than long. The carapace is brown with a light streak along the medial keel. The plastron is large and the bridge broad. Both anterior and posterior plastral lobes are narrower than the middle section, and there is a deep anal notch. A spinelike anterior projection occurs on each gular of juveniles, but these become more blunt with age and are lost in adults. The plastral formula is: abd > pect > fem > hum > gul > an. Both axillary and inguinal scutes are present. Plastron and undersides of the marginals are yellow with radiating dark lines on each scute. The head is rather small with a slightly projecting snout and a narrow medial depression flanked on each side by a toothlike cusp on the upper jaw. Posterior head skin may be divided into scales. The head is grayish to brown with a yellow spot near the tympanum. Limbs are gray with some yellow spotting. The forelegs have enlarged overlapping scales on the anterior surface, and the hind feet are clublike with enlarged spinelike scales in adults. Thighs and base of tail also contain spiny tubercles; toes are only partially webbed.
Of its 52 chromosomes, 28 are macrochromosomes (18 metacentric or submetacentric, 10 telocentric or subtelocentric) and 24 microchromosomes (Carr and Bickham, 1986).
Males have slightly longer and thicker tails than do females.
Heosemys spinosa ranges from Tenasserim, Myanmar, and southern Thailand southward through Malaysia to Sumatra and Borneo, and numerous small Indonesian Islands. Recently, it also has been reported from Tawitawi (Fritz, 1997) and Mindanao (Das, 1996), Philippines.
Heosemys spinosa occurs in shallow, clear mountain streams in forests. It frequently wanders about on land in cool, humid, shaded areas, and often hides under plant debris or clumps of grass. Mertens (1971) observed that, at least in captivity, juveniles are more terrestrial than adults.
Herman (1993) observed captives at the Atlanta Zoo copulating on 9 February and 26 December. The mating behavior was apparently stimulated when the turtles on land were sprayed with water from a garden hose. The male became excited and chased the female into the water pool and attempted to mount her (Herman likened the copulatory behavior to that of the North American species Clemmys insculpta). Nesting behavior was not observed, but eggs were oviposited at night or in early morning and were usually found on top of the substrate or under cork bark. Only 1-2 eggs were laid per clutch (clutches containing three eggs are known), and up to three clutches were produced a year. The eggs are white and oblong. Hatchlings are large, that produced at the Atlanta had a 55.0 mm carapace when measured one week after hatching, and ten near-hatchling young measured by Ewert (1979) averaged 63.2 mm in carapace length. Herman (1993) reported that when approached, the hatchling would freeze in place, and even if handled would not move.
To accommodate the large eggs housing these young, a hinge develops in the female's abdominal scute allowing the plastron more flexibility during egg laying. This is achieved by an incomplete separation of the abdominal scute into hyoplastral and hypoplastral elements and by fragmentation of the inguinal scute (Waagen, 1984).
Heosemys spinosa apparently is largely herbivorous, preferring fruits and various vegetables, but in captivity it may accept some animal foods, such as canned dog food and chopped mice (added to a fruit/vegetable salad; Herman, 1993). The hatchling at the Atlanta Zoo would not eat until offered chopped tomatoes. After two weeks on a diet of tomatoes it finally accepted a mixed fruit/vegetable salad.
IUCN Red List Status (1996)