Pseudopenilidae

Korovchinsky, Nikolai M. & Sergeeva, Nelli G., 2008, A new family of the order Ctenopoda (Crustacea: Cladocera) from the depths of the Black Sea, Zootaxa 1795, pp. 57-66 : 58-59

Pseudopenilidae fam. nov.

Head large and clearly separated from trunk, eye small with small number of ommatidia, ocellus present. Antennules comparatively large, with long sensory seta and five aesthetascs. Second antennae long and massive, with large basipodite, having dorsally some transverse rows of denticles and comparatively long twosegmented branches armed with long, one-segmented, needle-shaped setae without setules. System of mouthparts possesses mandibles, highly transformed maxillules (mx I) without long setae and lacks second maxillae (mx II). Shell, covering all trunk and thoracic limbs, has a prominent dorso-posterior margin, bearing, together with dorsal and postero-ventral valve margins, a row of denticles. Brood pouch closed. Six pairs of similar thoracic limbs without gnathobases and filtering setae. Each limb consists of long leaf-like exopodite with five-six comparatively short terminal setae without setules and shorter endopodite, bearing one long terminal thorn-shaped seta and few long thin setae. Small epipodite present only on thoracic limbs of first pair. Postabdomen wide and massive, with two rows of small dorsal prominences, bearing small denticles, and two massive terminal claws. Setae nanatoriae long, one-segmented, needle-shaped and lack setules. Resting eggs oval, with thin hard outer shell covered with small prominences.

Remarks. General body structure and other specific features of the new family are quite similar to those of family Sididae (Table I).They have large head clearly separated from the trunk, a frontal eye and ocellus, comparatively large antennules with long terminal sensory seta and aesthetascs, large second antennae with long massive basipodite and long branches, setae of which occupy both terminal and lateral position. The main feature, uniting all cladoceran Ctenopoda , presence of six pairs of similar thoracic limbs with wide leaflike exopodite, is also present as well as the wide massive postabdomen with stout terminal claws and resting eggs with hard outer shell.

TABLE I. Comparison of morphological features of taxa of the order Ctenopoda of family rank.

Morphological features Pseudopenilidae Sididae Holopediidae

fam. nov. Sidinae Penilinae

Body not covered by gelatinous envelope + + + - Head large + + + - Eye small with small number of ommatidia + - + + Ocellus present + +* - + Antennules with few (5-6) aesthetasks + - + + Second antennae of females and males with two branches + + + - Both antennal branches (if present) two-segmented + - + + Antennal setae one-segmented, needle-shaped and lack setules + - - - Antennal setae occupy both terminal and lateral position + + + - Maxillules (mx I) without long setae + - - - Maxillae (mx II) absent + - - - Shell covers thoracic limbs and postabdomen + + + - Brood pouch closed + - + - Six pairs of similar thoracic limbs + + + + tl VI not strongly transformed comparatively to other limbs + - - - Thoracic limbs with reduced epipodites + - + - Thoracic limbs without gnathobases and filtering setae + - - - Setae of exopodites of thoracic limbs without setules + - - - Massive postabdomen with stout terminal claws + + + + Setae nanatoriae one-segmented and lack setules + - - - Resting eggs with hard outer shell + + + +

* Ocellus is absent in genus Diaphanosoma .

At the same time, the presence of some unusual morphological features of Pseudopenilia such as the specific structure and armament of antennules, antennal setae, mouth parts, and thoracic limbs clearly separate it from sidids.

Type genus: Pseudopenilia Sergeeva, 2004 , diagnosis of which corresponds to that of family Pseudopenilidae .

Type species of the genus Pseudopenilia – Pseudopenilia bathyalis Sergeeva, 2004 .