(Duméril and Bibron, 1835)
Hilaire's side-necked turtle
Recognition
This large species (to 40 cm) has an oval, flattened, carapace with parallel sides, is broadest near the center, and has a smooth posterior rim. There is a slight medial groove on the depressed dorsal surface, and a weak keel may be present on younger individuals. Vertebral 1-3 and 5 are broader than long in adults, but the 4th is as long as or longer than broad (all are broader than long in juveniles); the 1st is expanded anteriorly and largest, the 5th expanded posteriorly. The cervical scute is usually long and narrow. The carapace is dark brown, olive, or gray, with a yellow border; the scutes are often rugose. The plastron is well-developed and has an anal notch. Its forelobe is much broader than the hindlobe, and the bridge is relatively broad. The plastral formula is quite variable: intergul >< fem >< abd >< an > gul > hum > pect; the intergular completely separates the gulars. The undersides of the marginals, bridge, and plastron are yellow with numerous irregularly shaped black spots. The head is large and broad with a projecting snout, two bicolored chin barbels, and an upper jaw lacking both a notch and a hook. Dorsally, the head is covered with irregularly shaped scales, but the frontal scute is prominent. The head is gray to olive above with a pronounced black stripe on each side which begins at the nostril and runs backward through the orbit and over the tympanum to the neck. Below this stripe the head and neck are white to cream. Another black stripe is usually present on each side of the throat, beginning behind the barbel and running backward to sometimes join the upper black stripe. The jaws are yellow, and the neck may contain some blunt tubercles. Limbs are gray to olive on the front and sides but cream colored beneath; soles and palms of the feet may be black.
Males have longer, thicker tails and concave plastra.
Distribution
Phrynops hilarii ranges in Brazil from Buenos Aires southward and westward into Uruguay and Argentina; possibly also in Paraguay and Bolivia.
Habitat
This turtle is found in oxbows, swamps, lakes, and ponds with soft bottoms and abundant aquatic vegetation.
Natural History
Courtship behavior was described by Fritz and Mann (1993). In Argentina, reproduction starts in November-December and may last to February-March (Cei, 1993). A clutch consists of 22-23 spherical eggs (27-31 mm in diameter, weighing 15-17 g), which are laid in nests dug in beaches (Freiberg, 1981; Cei, 1993). Incubation takes 60-70 days (Cei, 1993). Hatchlings we have examined had keeled, oval carapaces of 33-35 mm with very rugose scutes; coloration and patterns were like those of the adult but brighter.
Freiberg (1981) and Cei (1993) reported that wild Phrynops hilarii feed on fish, larval and adult amphibians and mollusks, but captives will eat meat and some fruits (Fritz and Schneider, 1995).
IUCN Red List Status (1996)
Not listed.