Desmosomidae Sars, 1899

Riehl, Torben & Brandt, Angelika, 2010, Descriptions of two new species in the genus Macrostylis Sars, 1864 (Isopoda, Asellota, Macrostylidae) from the Weddell Sea (Southern Ocean), with a synonymisation of the genus Desmostylis Brandt, 1992 with Macrostylis, ZooKeys 57, pp. 9-49 : 10

Desmosomidae Sars, 1899

Macrostylini Hansen 1916 p. 74; Wolff 1956 p. 99

Macrostylinae Birstein, 1973

Macrostylidae Gurjanova 1933, p. 411; Menzies 1962a, p. 28; 1962b, p. 127; Wolff 1962, Menzies and George 1972, p. 79-81; Wägele 1989, Brandt 1992; 2002; 2004; Birstein 1970, Kussakin 1999, p. 336; Mezhov 1988, p. 983-994; 1992, p. 69

Composition.

Macrostylis Sars, 1864

Type genus.

Macrostylis Sars, 1864

Diagnosis.

Cephalothorax free, about as broad as long. Body elongated. Eyes absent. Antenna 1 small, number of articles variable (1-9). Antenna 2 short or only moderately long, with articles 1-3 together about as long as articles 4 and 5 respectively, squama absent. Mandible with pars molaris reduced, subacute triangular and setiferous on apex; palp absent; lacinia mobilis ambilateral. Maxilliped with long and narrow basis; subtriangular epipod subequal in length to basis; palp articles 1-3 expanded and articles 4-5 minute.

Pereonites 1-3 constituting separate subquadrangular section with tightly articulated segments but tergite borders visible: fossosome. Pereonites 4-7 articulated moveably, constricted anteriorly. Pereopods 1-4 fossorial; pereopods 1-3 dactylus with 2 (anterior and posterior) subterminally inserting claws and posterior to both claws with elongated expansion, proximodorsally to claws with 2-3 sensillae, exceeding the distal tip in length. Pereopod 3 most robust, strongly setiferous, ischium extended dorsally, with row of long setae, with 1-2 apical setae strongly pronounced (spine-like, thickened, bent), merus distally extended; orientation of propodus twisted 180° along proximo-distal axis compared to pereopods 1-2, hence, propodus and dactylus bent in dorsal direction instead of ventral. Pereopod 4 shortest, bent laterally at mero-carpal articulation, directed in lateral or laterodorsal position. Posterior pereopod articles elongate subcylindrical. Pereopodal coxae inserted lateroventrally.

Coxae 1-3 inserted at anteriolateral margins of pereonites, coxae 4 inserted medially, coxae 5-7 inserted under posterolateral protrusions.

Sternite of pleonite 1 distinguishable; pleopodal articulations merged together at anterior margin of branchial cavity; anus subterminally, separated from branchial cavity in longitudinal ventrocaudal excavation stretching from branchial cavity to pleotelson apex. Female operculum oblong, distally with long pappose setae covering anal chamber. Uropods with 1-, 2- or many articles, elongated, terminally articulated, uniramous. Pleotelson with a pair of statocysts.