Phrynops tuberculatus

(Luederwaldt, 1926)
Tuberculate toad-headed turtle

The oval, slightly domed carapace (to 25 cm) is medially keeled, broadest behind the center, and has a smooth to slightly serrated posterior rim. The cervical scute is broad. Vertebrals are broader than long; the 1st is expanded anteriorly and the 5th is laterally flared posteriorly. The vertebral keel is discontinuous and a shallow longitudinal groove parallels it on each side; in old individuals these grooves may join posteriorly to form a single medial groove. Posterior marginals may be slightly raised above the tail. The carapace is light to dark brown or black; the surface of each scute may be roughened with raised striations. The plastron is well-developed and covers much of the carapacial opening. Both lobes are of about equal breadth; the forelobe is rounded anteriorly, while the anal scutes of the hindlobe are tapered toward the rear and posteriorly notched. The intergular scute is well-developed and usually longer than its distance from the abdominals; it completely separates the gulars. The plastral formula is quite variable: intergul >< fem >< an >< abd > gul > pect > hum. On the bridge, the inguinal scute is larger than the axillary, if one is present. The plastron varies in color from uniformly yellow to yellow with dark seam borders to almost totally dark brown. The head is broad with a projecting snout, an unnotched upper jaw, and two chin barbels. Behind the orbits, the sides of the head bear numerous irregularly shaped scales; the skin between the orbits is unbroken. The neck may or may not contain conical tubercles. In color, the head varies from uniformly gray to gray with numerous pink or yellow speckles. Jaws are light brown and there may be light bars on the upper jaw. Neck and limbs are gray to brown, and the neck may be lightly speckled.
Males have longer, thicker tails, with the vent near the tip, and concave plastra.

Phrynops tuberculatus occurs in eastern Brazil, in the Rio São Francisco and adjacent drainages.

Geographic Variation
Unknown; Phrynops vanderhaegei was originally described as a subspecies but is now considered a full species.

Presumably, Phrynops tuberculatus is an inhabitant of small rivers and streams.

Natural History
Grossmann and Reimann (1991) described courtship in this species. The male pursues the female until he faces her, and then lays his head on hers, slowly but increasingly faster swinging it from left to right. This behavior, with short interruptions, may last up to four hours. The male then approaches the female from behind, mounts her, grabs her carapace with his legs and presses his cloaca onto hers; the female, undisturbed, swims on. The mounting phase was observed for up to 25 minutes. A clutch has 4-9 eggs (32 x 26 mm, 11.4-13.3 g), and hatchlings are 37 mm (Grossmann and Reimann, 1991).
According to Grossmann and Reimann (1991), Phrynops tuberculatus in the wild feeds on fish, carrion, insects, snails and worms, and is crepuscular and very secretive. Bour (1973) reported that captives ate earthworms, insects, and fish.

IUCN Red List Status (1996)
Not listed.