Tryphosa, Boeck, 1871

Kilgallen, N. M. & Lowry, J. K., 2014, The Tryphosa group (Crustacea: Amphipoda: Lysianassoidea: Lysianassidae: Tryphosinae), Zootaxa 3768 (5), pp. 501-545 : 503

Tryphosa group

Diagnostic description. Antenna 1 well developed, accessory flagellum forming a cap. Mandible molar columnar with convex triturating surface or proximally setose and distally triturating. Gnathopod 1 subchelate or parachelate. Uropod 2 inner ramus constricted. Telson cleft.

Included genera. The Tryphosa group includes 8 genera: Bruunosa Barnard & Karaman, 1987 ; Glorieusella gen. nov.; Gronella Barnard & Karaman, 1991 ; Metambasia Stephensen, 1923 ; Pseudonesimus Chevreux, 1926 ; Schisturella Norman, 1900 ; Thrombasia J.L. Barnard, 1966 ; and Tryphosa Boeck, 1871 .

Remarks. This interesting group is highlighted by two synapomorphies: the accessory flagellum forms a cap that covers the callynophore, and the inner ramus on uropod 2 is constricted. The characters defining the genera are mainly confined to gnathopod 1; strongly or weakly subchelate and the condition of the coxa from fully developed to vestigial, tapering or subrectangular.

Two genera, Gronella and Metambasia , are North Atlantic arctic/boreal endemics. Three of the more widespread genera, Pseudonesimus , Schisturella and Thrombasia , occur in Australian waters.

Within the Tryphosa group species gnathopod 1 is either strongly subchelate, subchelate or parachelate and three kinds of gnathopod 1 coxae are found: subrectangular and about as big as the gnathopod 2 coxa; slightly smaller than gnathopod 2 and tapering; or vestigial. There are two forms of the maxilla 1 setal-teeth: either both ST-7 and ST-D have the medial margin mostly or completely serrate or the medial margin is smooth and they are apically serrate or cuspidate. The uropod 3 rami may be either with plumose setae in the adult male and/or female or they have no plumose setae; and the lanceolate inner ramus is either slender or broad. These combinations of characters define the genera in the Tryphosa group.