This family, still represented by nearly thirty species, which are divided into eight genera, is restricted to Notogaea, namely, South America and Australia.
Fig. 87.–Skull of Chelys fimbriata. × 1. A, Dorsal view of skull; B, side view of skull and hyoid apparatus. Cop, copular piece; F, frontal; J, jugal; L.o, lateral occipital; Mand, mandible; Op, opisthotic; Orb, orbit; Par, parietal; Pt.f, postfrontal; Ptg, pterygoid; Q, quadrate; Qj, Quadrato-jugal; Sq, squamosal; I, II, First and second branchial arch.
Chelys fimbriata, the "Matamata," the only species of this genus, inhabits the rivers of Guiana and Northern Brazil. Besides the nuchal, there are seven neural plates; the last pair of costals form a median suture. Nasal bones are absent. The jaws are very weak. The Matamata has a very peculiar appearance. The nose is produced into a long, soft tube, at the end of which open the tiny nostrils. The eyes are very small, and the orbits are placed very near the anterior end of the skull, while the parietal region is broad and much elongated (Fig. 87, p. [400]). The quadrates are drawn out into trumpet-shaped tubes. The hyoid apparatus is very large, with enormous anterior and posterior horns. The head and neck are as long as or even longer than the carapace, which is covered with thick, lumpy shields. The skin of the thick neck, of the sides and under parts of the head, is produced into many soft arborescent excrescences or fimbriae, those of the chin and throat and the large ear-flaps being movable at will, and probably used to attract fishes and other prey. The tail is very short. The fore- and hind-limbs are webbed, the former with five, the latter with four claws. Old specimens, which reach a total length of three feet, are uniformly dark brown, and look like a log covered with rough bark. The young are far less ugly, with black and yellow spots on the shell, and with dark stripes along the neck.
Fig. 88.–Chelys fimbriata ("Matamata"). × ⅒.
Very little is known about the habits of this peculiar creature. It is said to lie submerged in the water, waiting for fishes, frogs, or tadpoles, which are attracted by the playing motions of its cutaneous excrescences. The jaws being so weak, and being covered with a partly soft lip-like skin, it is probable that they are not used for seizing the prey, but that the latter is engulfed into the mouth with the inrush of water into the throat. That this can be widened enormously is indicated by the greatly developed hyoid apparatus.
Chelodina.–The neck is long and slender, the head small and smooth. The nuchal is terminal; the intergular is large. The neural plates are completely suppressed, all the eight pairs of costal plates meeting in the middle line. The shell is very flat. Anterior and posterior limbs entirely webbed, and with only four claws. The tail is very short. Three species in Australia, one in New Guinea.
Fig. 89.–Chelodina longicollis. × ⅓.