(Owen, 1853)
Bibron's giant softshell turtle
Recognition
The smooth, brown adult carapace (to 102 cm) bears irregular yellow to buff marks on the side of the central disc, often as wide bars. The pliable rim also has numerous irregular light mark is and a narrow yellow rim. A few low tubercles are situated in the cervical region. The soft parts are brown to black. The neck bears prominent yellow or buff longitudinal stripes, and similarly colored irregular marks appear on the limbs. No vertical cusp-edged scales are present along the lower margin of the forelimb. Juveniles are patternless with a rough-textured pale brown carapace. Carapace tubercles are either isolated or in continuous rows, and vermiform tubercles are present on the dorsal and lateral surfaces of the neck. The adult pattern begins to appear soon after the turtle has grown to 10 cm carapace length.
Distribution
Bibron's giant softshell is restricted to southern New Guinea from the Fly River-Lake Murray drainage east to at least the Brown-Laloki watershed in Papua New Guinea, and as far west as the Setakwa River in Indonesian Irian Jaya (Webb, 1995).
Geographic Variation
Unknown.
Habitat
Primarily inland freshwater rivers and streams, but coastal records do exist (Rhodin et al., 1993).
Natural History
Nesting takes place from June to August, and possibly in September, and at times the debris of crocodile nests is used (Rhodin et al., 1993). Waite (1903) reported that P. bibroni lays up to 27 eggs in a clutch, but that a full complement of eggs is not deposited at one time. Probably at least two clutches are laid each season. Rhodin et al. (1993) reported that 20-45 eggs comprise a clutch, and that there is an unconfirmed record of a clutch containing 100 eggs.
Apparently, crocodiles are the only predators of adults.
Remark
The original description of this turtle was based on a skull and skeletal parts of one individual in the collection of the Royal College of Surgeons, London. Unfortunately, the holotype was destroyed during the bombing of London in World War II. The type-locality was listed as "Australian" (Owen, 1853), a possible error since the species is not known from Australia. Webb (1995) designated a neotype, Australian Museum 3424 (a large stuffed female), 3426 (viscera) and 131315 (re-catalogued skull, lower jaw and hyoid apparatus) to replace the lost holotype. The specimen (from the Laloki River, Astrolabe Range, 40 miles from its entry into Redscar Bay, Central District, Papua New Guinea) was the first Pelochelys reported in the literature from New Guinea (Waite, 1903). The neotype designation restricts the name bibroni to the distinctive population in southern New Guinea, geographically the closest to the alleged original type-locality of Owen (1853).
IUCN Red List Status (1996)
Vulnerable (A1cd); the distributions of P. bibroni and P. cantorii have been switched in the online 1996 Red List (Brian Groombridge, pers. comm.).