Pliotrema, Regan

Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, PLOS ONE 15 (3), pp. 1-56 : 53

Key to the valid species of Pliotrema

1a. Five pairs of gill openings, large lateral rostral teeth smooth.. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .... . Pristiophorus

1b. Six pairs of gill openings, large lateral rostral teeth serrated ( Pliotrema ).. .... ... ... ... ... ... .... ‥.. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .... ‥ 2.

2a. Barbels about two thirds way from rostral tip to mouth, with prebarbel length about twice distance from barbel origin to symphysis of upper jaw; rostrum not constricted between barbel origin and nostrils; a pronounced yellowish longitudinal stripe on dorsal surface.. ... ... ... ... ... ... ... ... ... ... .... Pliotrema warreni [ South Africa, southern Mozambique].

2b. Barbels about half way from rostral tip to mouth, with prebarbel length about equal to distance from barbel origin to symphysis of upper jaw; rostrum constricted between barbel origin and nostrils; dorsal surface without or with two longitudinal stripes.. ... ... ... ... ... ... .... ‥ 3.

3a. Snout long, head length 38.3–40.4% TL, preorbital length 25.7–27.3% TL, preoral length 28.6–31.3% TL, prebarbel length 14.8–16.2% TL, barbel origin to symphysis upper jaw 13.7– 15.0% TL; rostrum clearly constricted between barbel origin and nostrils; 21–31 large lateral rostral teeth; 38–43 upper jaw tooth rows, jaw teeth with sharp basal folds; pale to light brown dorsally with two yellowish stripes, uniform white ventrally, posterior fin margins with narrow white edges.. ... ... ... ... ... ... .... Pliotrema kajae sp. nov. [ Madagascar, Mascarene Ridge].

3b. Snout short, head length 34.2–34.5% TL, preorbital length 21.7–22.0% TL, preoral length 24.6–25.1% TL, prebarbel length 12.6–12.7% TL, barbel origin to symphysis upper jaw 12.1– 12.3% TL; rostrum only slightly constricted between barbel origin and nostrils; 16–17 large lateral rostral teeth; 35–37 upper jaw tooth rows, jaw teeth without basal folds; uniform medium to dark brown dorsally without longitudinal stripes, white ventrally but with few indistinct dark blotches on belly, posterior fin margins conspicuously white-edged.. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .... ‥... Pliotrema annae sp. nov. [ Zanzibar].