Deevey and Brooks, 1980
Diagnosis
Sibling species to C. mamillata (Conchoecia mamillata). Carapace, height about 40% length, with a slight anterior taper, margin curves smoothly from rostral incisure to postero-dorsal corner (C. nanomamillata Habitus 1, C. nanomamillata Habitus 3). Right valve with spine at the postero-dorsal corner and left valve with tubercle just below its corner. Left asymmetrical gland opening on tip of tubercle, and right symmetrical gland opening on another prominent tubercle at mid-height on the posterior margin. The tubercles on the posterior margin give species in the mamillata group an instantly recognisable profile. A criss-cross pattern of striations covering the whole surface of the carapace.
Female, frontal organ nearly three times the length of first antenna, capitulum differentiated, slightly drooping, spinose and swollen in its distal half (C. nanomamillata 1). First antenna with short dorsal seta extending only to the end of the limb, the sensory setae ("a"-"d") are about 60-70% of the "e" seta (cf. 50% in C. mamillata ). Second antenna, endopodite, "b" seta carries a tuft of hairs (C. nanomamillata 2), terminal setae are all subequal.
Male, frontal organ capitulum down-turned and enormously swollen at its end (C. nanomamillata 3). First antenna, "a" seta nearly as long as the limb, "c" seta short, "b" seta distally carries a fringe of hairs and is subequal to the "d" seta, "e" seta is a little longer with armature of a double row of fine hairs (C. nanomamillata 4), distal to which the seta is sharply angled and flattened into a sword-shape. The second antenna is similar to that of C. mamillata .
Remarks
This species was described from off Bermuda, being initially distinguished on the basis of its smaller size. It occurs abundantly at 30°N 23°W at shallower depths (1000-1500m) than its larger sibling (>1500m). Like so many of the shallow bathypelagic species which seem to occur both in subtropical waters and temperate waters in the Northeast Atlantic, this species occurs sporadically in this region.
Distribution
So far only known from the Atlantic but seems likely to occur in all oceans. 48°N-30°N in Atlantic. 1 (R.R.S. Discovery Map).
Type specimens
Holotype dissected male mounted on a slide. Deposited in the National Museum of Natural History, Smithsonian Institution.
Type locality
32°10'N 64°30'W, Station S in the Sargasso Sea, 15 miles southeast of Bermuda.