Sophrosynidae, Lowry & Stoddart, 2010

Lowry, J. K. & Stoddart, H. E., 2010, Sophrosynidae, a new family in the Lysianassoidea (Crustacea: Amphipoda) with a revision of the genus Sophrosyne, Zootaxa 2370 (1), pp. 1-35 : 2-3

Sophrosynidae fam. nov.

Diagnostic description. Head exposed, slightly longer than deep, without cheek notch. Antennae calceoli absent in male and female. Antenna 2 peduncular article 3 without distal hook. Epistome and upper lip fused. Mouthpart bundle subquadrate. Mandible incisors present, well developed, symmetrical, straight, smooth; left lacinia mobilis rod-like, right lacinia mobilis absent; accessory setal row absent, without distal setal tuft; molar absent; palp present, inserted distally to extremely distally. Maxilla 1 inner plate with 2 or less apical pappose setae; outer plate with 2 apical primary setal-teeth and vestigial setal-teeth down medial face; palp large, with apical robust setae. Maxilla 2 inner plate subequal to or slightly shorter than outer plate, or inner plate significantly shorter than outer plate; inner plate without oblique row of facial setae. Maxilliped coxa and basis normal; outer plate present, medial setae absent, apical slender setae present; palp 4-articulate, article 4 well developed.

Gnathopod 1 slightly chelate; coxa large, about as long as coxa 2; merus and carpus not rotated; ischium short; carpus compressed; propodus large; dactylus slightly curved. Gnathopod 2 coxa large, subequal in size to coxa 3; propodus subquadrate to rectangular (less than 4 x as long as broad), with complex setae; dactylus minute. Pereopods all simple; distal spurs absent. Pereopod 4 coxa with well developed or weak posteroventral lobe. Pereopod 5 coxa anterior and posterior lobes subequal. Pereopod 6 coxa posterior lobe subequal to, slightly longer than or much deeper than anterior lobe.

Uropod 2 inner ramus without constriction. Uropod 3 rami biramous; outer ramus 2-articulate. Telson present, cleft or entire.

Additional characters. Antenna 2 subequal in length to antenna 1; peduncular article 3 short. Mandible incisors small; palp article 3 slender, blade-like, long. Maxilla 1 outer plate narrow; palp 2-articulate. Maxilliped inner plate small; outer plate very small, subrectangular; palp large, article 3 long. Gnathopod 1 coxa anterior margin slightly convex, anteroventral corner rounded; basis broad; carpus subtriangular; propodus subrectangular, posterior margin smooth; palm slightly obtuse, smooth. Gnathopod 2 ischium long; propodus posterodistal corner without robust setae. Pereopod 4 coxa deeper than wide. Pereopod 7 basis expanded posteriorly. Uropod 3 peduncle short; rami lanceolate.

Generic composition. Sophrosyne Stebbing, 1888 .

Remarks. Unlike the highly modified Euonyx which is clearly related to Stephonyx , it is difficult to know how Sophrosyne is related to other lysianassoid taxa. The mouthpart morphology is very reduced, particularly the reduced setal-tooth arrangement on the outer plate of maxilla 1, but also the absence of a molar, the reduction of setae on the inner and outer plates of maxilla 2 and the reduction of the inner and outer plates of the maxilliped. The setal-tooth arrangement is so modified that we cannot relate it to any of the standard lysianassoid arrangements and the molar has been independently lost at the family level as many as 15 times. At least eight other family level taxa within the lysianassoids have the inner plate of maxilla 2 reduced to half the length of the outer plate.