Acarnus Gray 1867

Identification key for the Western Atlantic species of Acarnus (Details of spicule set in Table 4) 1a. Three types of megascleres............................................................................. 2 1b. Four or more types of megascleres........................................................................ 3 2a. Megascleres as styles, tylotes, cladotylotes................................................................. 5 2b. Megascleres as tylotes, cladotylotes I and acanthostyles.............................................. A. radovani 3a. Megascleres as styles, tylotes, cladotylotes and acanthostyles.................................................. 4 3b. Megascleres as styles, tylotes, cladotylotes and tylostyles................................ Acarnus tupiniquim sp. nov. 4a. Two categories of cladotylotes.......................................................................... 6 4b. A single category of cladotylotes................................................................. A. souriei 5a. Cladotylotes I spined.................................................................................. 7 5b. Cladotylotes I smooth...................................................................... A. innominatus 6a. Two types of microscleres (toxas and chelae)............................................................... 8 6b. Three types of microscleres (toxas, chelae and microxeas).......................................... A. microxeatus 7a. Two categories of toxas................................................................................ 9 7b. Three categories of toxas........................................................................ A. toxeata 8a. Palmate isochelae <21µm (14.4–21µm)........................................................... A. nicoleae 8b. Palmate isochelae> 21µm (29.2–39.9µm).............................................. Acarnus hooperi sp. nov. 9a. Toxas I (accolada) and II (deeply-curved) present..................................................... A. tortilis 9b. Toxas II (deeply-curved) and III (oxhorn) present.................................................. A. deweerdtae