Hardella thurjii

(Gray, 1831b)
Crowned river turtle

The ellipsoidal, moderately domed adult carapace (to 61 cm) lacks marginal serrations but is notched posteriorly. It also contains a low, blunt medial keel, and, in some populations, also two low lateral keels. The carapace is widest just behind the center and highest at the seam separating the 2nd and 3rd vertebrals. Vertebrals are broader than long, and the keel is reduced to a posterior knob on each. Marginals are slightly flared in adults, but to a greater extent and somewhat serrated in juveniles. Neurals are elongated, six sided, and shortest anteriorly, and those posterior are decidedly broader than those anterior. The carapace is dark gray, brown, or black with a yellow outer rim (at least in younger individuals) and yellow pigment at the junction of the pleural and marginal scutes. The plastron is firmly and extensively sutured to the carapace and has strong, large buttresses. Axillary buttresses are connected to the 1st ribs, and inguinal buttresses attach midway along the suture between the 5th and 6th costals. The plastron lacks a hinge and has a relatively narrow hindlobe (narrower than the bridge) which is notched posteriorly. The entoplastron lies anterior to the humero-pectoral seam. The plastral formula is: abd > pect >< fem > hum > an > gul. Both plastron and bridge are yellow with a large dark blotch on each scute. In the skull, the chamber for the paracapsular sac is completely open posteriorly, a feature shared only with cheloniid sea turtles and some Mesozoic turtles. The squamosal bone is attached to the jugal and postorbital bones. The frontal enters the orbital border, but does not pass under the olfactory nerves. The canal for the carotid artery lies between the prootic and pterygoid bones, the orbito-nasal foramen is large, and the choanae open behind the orbits. Triturating surfaces are broad, and that of the upper jaw has a tuberculate medial ridge. The upper jaw is notched medially and the lateral borders of both jaws are serrated. The snout is blunt and only slightly projecting. The head is brown to black with several yellow stripes: one begins over the nostrils and extends backward above the orbit and then dips downward before extending onward to the neck, a second forms a bar across the upper jaw below the nostrils, and a third extends from the corner of the mouth backward along the neck. Occasionally other yellow marks occur on the dorsal surface of the head, or the long stripes may be interrupted. Dorsally, the snout and head are covered by a single large scale; the posterior surface of the head is covered with many small scales. All toes are webbed and the brown limbs have a yellow outer border.
There seems to be extreme sexual size dimorphism in this species: adult males reach about 17.5 cm in carapace length but adult females may be more than three times this length. The male tail is thick and long, and the plastron concave.

Hardella thurjii occurs in the watersheds of the Ganges, Brahmaputra, and Indus rivers in Bangladesh, northern India, and Pakistan. Minton (1966) also reports a single record for a coastal mangrove swamp near Karachi, Pakistan; a record from near Bombay, India (Grumwaldt, 1980) is probably in error.

Geographic Variation
Hardella thurjii thurjii (Gray, 1831b), the Ganges crowned river turtle, is found in the Ganges and Brahmaputra rivers has only a medial carapacial keel, while the Indus crowned river turtle Hardella thurjii indi Gray, 1870b from the Indus River system has a pair of low lateral keels as well as a medial keel. McDowell (1964) recognized H. indi as a probable species and Das (1991) presented it as a subspecies of H. thurjii. At present it seems best to recognize it as a poorly defined subspecies.

This large species prefers water bodies with slow current, mud bottoms, and abundant aquatic vegetation. It has been taken from or observed in oxbows, ponds, canals, and quiet pools in rivers.

Natural History
Courtship occurs in shallow water from April to July; the male produces a drumming sound with his forelimbs and mouth to mouth contact may occur (Das, 1995). Although nesting occurs in August and September, Das (1991) reports a December oviposition. Nests are dug in sandy soil, entirely with the hindlimbs. Clutches contain 14-19 elongated (51 x 34 mm) eggs (Das, 1995). Hatchlings are more brightly colored than adults. Their carapaces are 53.7-62.0 mm (Das, 1995) and more sharply serrated, and the vertebral keel more pronounced than in adults.
Hardella thurjii is normally a strict herbivore, naturally feeding on aquatic plants, but Minton (1966) observed one small individual eat part of a frog. In captivity they accept a variety of common fruits and vegetables.
These turtles rarely come out of the water to bask, but may do so by floating quietly at the surface. Minton (1966) reported they spend much time resting on the bottom. Hardella is of calm disposition, seldom biting when handled.

IUCN Red List Status (1996)
Lower risk: near threatened.