PLATYTHELPHUSIDAE Colosi, 1920

Reed, Sadie K. & Cumberlidge, Neil, 2006, Brachyura: Potamoidea: Potamonautidae, Platythelphusidae, Deckeniidae (), Zootaxa 1262 (1), pp. 1-139 : 1-139

FAMILY PLATYTHELPHUSIDAE Colosi, 1920

Platythelphusinae Colosi, 1920: 9 .

Potamonidae — Capart, 1952: 43–45.

Potamonidae — Bott, 1955: 221–222

Potamonautidae — Bott, 1970: 327–344; Coulter, 1991: 253 Cumberlidge, 1999: 119–120; Cumberlidge et al., 1999: 1489–1492; Marijnissen et al., 2004: 514–515.

Type genus. Platythelphusa A. Milne­Edwards, 1887 .

Diagnosis. Carapace outline subhexagonal, rounded; frontal margin lined by small teeth or distinct granules; external angles of front either marked by sharp spines or by small granules; stout triangular process (which may be produced into a small tooth, the descending frontal tooth) beneath external angles descending into orbital hiatus; anterolateral margin of carapace behind exorbital tooth with an epibranchial tooth plus from two or three large forward­directed pointed teeth. Suborbital margin lined by small teeth or small granules, medial end marked by either distinct spine or small tooth. Postfrontal crest distinct but incomplete, never meeting anterolateral margins. Anterolateral margin always lacking intermediate tooth between exorbital and epibranchial teeth.

Distribution. Lake Tanganyika, East Africa.

Remarks. The platythelphusids were originally established as a subfamily by Colosi (1920). Although this distinctive group of freshwater crabs was later treated as a subgenus of Potamonautes by Bott (1955), it was recognized as a distinct family by Cumberlidge (1999), Cumberlidge et al. (1999) and Marijnissen et al. (2004). In the present work, the Platythelphusidae includes a single genus ( Platythelphusa ) with nine species, all of which are endemic to Lake Tanganyika. Capart (1952) included Platythelphusa in the family Potamonidae Ortmann, 1896 , which was later emended to the Potamidae (Opinion 712, Bull. Zool. Nomenclature, 21, 1964). Bott (1955) originally assigned Potamonautes (Platythelphusa) to the Potamonidae (= Potamidae ); later, Bott (1970) transferred this genus to the Potamonautidae Bott, 1970 and this arrangement was accepted by Coulter (1991). Cumberlidge (1999) raised the monotypic subfamily Platythelphusinae Colosi, 1920 to the rank of a full family, the Platythelphusidae , which included the genus Platythelphusa and this arrangement has been accepted by most subsequent authors ( Martin & Davis 2001; Marijnissen et al. 2004). These three families are viewed here as separate phylogenetic entities, based on the results of the cladistic analyses of the relationships between the platythelphusids, potamonautids and deckeniids by Sternberg et al. (1999), Cumberlidge & Sternberg (1999) and Sternberg & Cumberlidge (1999, 2001). This family was revised by Cumberlidge et al. (1999) and Marijnissen et al. (2004) and these works together provide detailed illustrations of the carapace and gonopods of all species. For this reason these characters have not been redrawn here, although photographs of all nine species of Platythelphusa are included (Plates XVII to XXV).

Natural history and conservation status. The platythelphusids are completely aquatic crabs. They have never been observed out of water and they die after a few hours in dry air (S. Marijnissen, pers. comm.).

Platythelphusa A. Milne­Edwards, 1887 (Figs. 189–197, plates XVII–XXV)

Platythelphusa A. Milne­Edwards, 1887: 146 ; Hilgendorf, 1898: 21; Moore, 1903: 286; Rathbun, 1905: 268; Cunnington, 1907: 266–268; 1920: 557; Alcock, 1910: 253–261; Colosi, 1920: 9– 10; Cunnington, Balss, 1936: 196; Chace, 1942: 224; Cumberlidge, 1999: 16, 17, 25, 36, 37, 42, 45, 66–69, 74, 76–79, 100–113, 116, 317; Cumberlidge et al., 1999: 1491–1493; Marijnissen et al. 2004: 515.

Limnothelphusa Cunnington, 1899: 698 ; Moore, 1903: 280; Rathbun, 1905: 269.

Hydrothelphusa (Platythelphusa) Bouvier, 1917a: 615–621 ; 1917b: 657–659; 1921: 41.

Potamonautes (Platythelphusa) Bott, 1955: 226–229 ; Coulter, 1991: 253–257.

Type species. Platythelphusa armata A. Milne­Edwards, 1887 , by monotypy.

Diagnosis. As for family.

Distribution. Known only from Lake Tanganyika, East Africa. Most (but not all) of the species of Platythelphusa have been collected from Tanzanian waters. Nevertheless, for completeness the genus is included in the present work in its entirety.

Remarks. Nine species of Platythelphusa are recognized here: P. armata A. Milne­ Edwards, 1887, P. maculata ( Cunnington, 1899) , P. conculcata Cunnington, 1907 , P.denticulata Capart, 1952 , P. tuberculata Capart, 1952 , P. polita Capart, 1952 , P. echinata Capart, 1952 , P. immaculata Marijnissen, Schram, Cumberlidge & Michel, 2004 , and P. praelongata Marijnissen, Schram, Cumberlidge & Michel, 2004 .