PEET: Leptostraca: Taxonomic keys

1a. Thoracic region appearing inflated. Carapace and body cuticle thin, membranous. Carapace lacking posterior medial indentation and with slight sculpturing. Mandible lacking incisor process and with reduced molar process. First maxilla with palp reduced to small stub. Second maxilla nearly as large as thoracopod 1; endopod 1-segmented and reduced to small, blunt, distal lobe; exopod absent; proximal endite enormously enlarged. Pleopods 2-4 with exopods paddlelike, less than 3 times longer than wide. Caudal rami leaflike, broadest at midpoint

Family Nebaliopsidae Hessler, 1984 (Nebaliopsis G. O. Sars, 1887)

1b. Thoracic region not inflated. Carapace and body cuticle more or less firm. Carapace strongly emarginate (indented) posteromesially and lacking sculpturing. Mandible with well developed incisor (Paranebalia is an exception to this) and molar process. First maxilla with palp long, well developed. Second maxilla much smaller than thoracopod 1; endopod 1-or 2-segmented; endopod and exopod well developed, each longer than wide; first three endites similarly developed (proximal endite not enormously enlarged although slightly larger than other endites). Pleopods 2-4 with exopods slender, more than 4 times longer than wide. Caudal rami tapering evenly from base to tip

2 (Family Nebaliidae Baird, 1850; emend. Hessler, 1984)

2a. Eyestalk long, clearly exceeding rostrum in mature individuals, gently curved or abruptly angled ventrally, tapering distally, lacking any visual pigment

2b. Eyestalk short, not exceeding length of rostrum in mature individuals (or, if exceeding length of rostrum, then not deflected ventrally [Speonebalia]), widest at midpoint (not tapering), with or without visual pigment

3a. Eyestalk with an abrupt angle on anterodorsal surface, and with anterior margin flattened and bearing minute lobes. Second maxilla with exopod reduced, less than half length of proximal article of endopod. Posterior emargination of carapace lacking minute spines along either side of midpoint. Thoracopods with well developed epipods

Dahlella Hessler, 1984

3b. Eyestalk smoothly curving on anterodorsal surface, banana- or sausage-shaped, not flattened on anterior margin, lacking minute lobes. Second maxilla with exopod more than half length of proximal article of endopod (usually exceeding length of proximal article of endopod). Posterior emargination of carapace minutely spinulose along either side of midpoint. Thoracopods lacking epipods

Nebaliella Thiele, 1904

4a. Pleopod 1 with row of stout, equally sized, complex serrate spines along outer (lateral) margin of exopod. Eyes with at least some visual pigment

4b. Pleopod 1 lacking row of stout, equally sized, complex serrate spines along outer (lateral) margin of exopod. Eyes lacking any visual pigment

5a. Carapace long, extending posteriorly to just beyond level of 5th pleonite, sometimes as far as 6th pleonite. Eyestalks narrow, tapering distally, slightly exceeding length of reduced rostrum. Maxilla 2 endopod 1-segmented, with series of oval organelles (glands). Rostrum lacking distal spine. Caudal rami very short, length approximately equal to width of telson, with densely spaced long setae

Speonebalia Bowman et al., 1985

5b. Carapace short, not extending posteriorly beyond 5th pleonite. Eyestalks laterally compressed, disc-shaped or subrectangular, never exceeeding length of rostrum. Maxilla 2 endopod 2-segmented, lacking glands. Rostrum with minute distal spine that articulates with rostral cuticle. Caudal rami slender, length more than twice length of telson, with widely spaced setae

Sarsinebalia Dahl, 1985

6a. Antenna 1 peduncle distal (fourth) segment with distolateral, toothed processes, but not with armature of spines (as e.g. in Nebalia). Mandibular incisor weakly developed. Thoracopods narrow and long, almost flagelliform. Epipods of thoracopods present but reduced in size, with surface area less than half that of endopod. Eyes often bearing spines that increase in size distally

Paranebalia Claus, 1880

6b. Antenna 1 peduncle distal (fourth) segment without distolateral, toothed process, instead with stout spines. Mandibular incisor well developed. Thoracopods expanded, leaf-like. Epipods of thoracopods with well developed epipods, surface area clearly 1/2 or more that of the endopod. Eyes sometimes with blunt lobes but never with numerous spines

Nebalia Leach, 1814