Colomastix, Grube, 1861

Guedes-Silva, Elkênita, Souza-Filho, Jesser F. & Tavares, Marcos, 2024, Three new species of Amphipoda (Crustacea: Peracarida) from the remote oceanic island of Trindade, off the coast of south-eastern Brazil, Journal of Natural History 58 (45 - 48), pp. 2075-2098 : 2081-2082

Key to species of Colomastix from Brazil (adult males)

1a. Gnathopod 1 vestigial .................................................................................................... 2

1b. Gnathopod 1 fully developed ..................................................................................... 4

2a. Head interantennal plate with anteroventral margin serrated ............................ ...................................................................................... C. trispinosa Silvany et al., 2019

2b. Head interantennal plate with anteroventral margin not serrated ............. 3

3a. Head subequal in length to pereonites 1 and 2 combined; pleopods 1–3 outer rami 4-articulate; uropod 1 inner ramus longer than outer rami; telson lateral margins smooth ................................ C. iemanja Silvany and Senna, 2019

3b. Head subequal in length to pereonite 1 and half-length of pereonite 2; pleopods 1–3 outer rami 4-articulate, inner ramus 3-articulate; uropod 1 inner ramus distal 1/4 of lateral margins closing upon itself, forming a tube with a terminal concavity; telson fringed with numerous short robust setae .... ...................................................................................... C. tubulosa Silvany and Senna, 2019

4a. Head interantennal plate with anteroventral angle projecting beyond anterodorsal angle; uropod 1 asymmetric, right uropod inner apex somewhat expanded and rudder-shaped, left uropod with the rudder-shaped structure atrophied; telson serrate posterolaterally, devoid of hook processes ..... .............................................................................. C. marielle Silvany and Senna, 2019

4b. Head interantennal plate with anteroventral angle not projecting beyond anterodorsal angle; uropod 1 male symmetric; inner ramus tip resembling a ‘venom gland and stinger of a scorpion’ in lateral view; telson ventrodistally with a pair of strong, curved hooks .................................. C. scorpio sp. n.