side-necked turtle, name for the long-necked turtle of the families Chelidae and Pelomedusidae, found only in the Southern Hemisphere. The neck in these two families is of a different structure from that of other turtles and is folded sideways under the shell for concealment instead of being pulled straight back. Members of the family Chelidae, sometimes called snake-necked turtles, are river turtles of South America and the Australia–New Guinea region. Several species have slender, elongated snouts. Among these is the matamata ( Chelys fimbriata ) of Brazil and N South America. The matamata is a weak-jawed turtle that lies in wait for its prey, chiefly fish, and sucks it up with the snout. Its shell has high bumps and is covered with moss and water plants, so that when motionless the turtle looks like a rock. The family Pelomedusidae includes two African genera, Pelomedusa and Pelusios. Members of the latter genus resemble the North American box turtles, with a hinged shell. A third genus, Podocnemis, is found in rivers of South America and Madagascar. Side-necked turtles are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia.