REVISION OF SIMOCEPHALUS DAPHNIIDAE 
MATERIALS AND METHODS 
About ten thousand specimens from more than three hundred locali- 
ties all over the world have been studied. Females of all species 
except S§. /usaticus, males of nine species, and museum types of 
fifteen taxa have been examined. Material examined is in the follow- 
ing collections and institutions: AC — author’s collection deposited 
in Zoological Museum of Moscow State University, AM — Austral- 
ian Museum, Sydney, Australia, BMNH — The Natural History 
Museum, London, Great Britain, MCA — Museum of Central Africa, 
Tervuren, Belgium, MNO — Museum of Nature, Olten, Switzerland, 
MV — Museum of Victoria, Australia, SAM — South Australian 
Museum, Adelaide, Australia, ZI — Zoological Institute of the Rus- 
sian Academy of Sciences, St.-Petersburg, Russia, ZICC — Cladocera 
collection of ZI, ZICW — G.Ju. Werestchagin’s collection in ZI, 
ZIPD — plankton depository of ZI, ZMC — Zoological Museum of 
Copenhagen, Denmark, ZMO — Zoological Museum of Oslo Uni- 
versity, Norway, ZMU — Zoological Museum of Uppsala University, 
Sweden. 
Original figures are made with the aid of a camera lucida. Keys 
and diagnoses are based on adult specimens. The following addi- 
tional abbreviations are used: CBS — canadian balsam slide, MPA — 
material preserved in alcohol, PSEM — preparation for scanning 
electron microscopy, PVAS — polyvinyl alcohol slide, 9 ad. — adult 
parthenogenetic female, 9 juv.—juvenile parthenogenetic female, ° e. 
— ephippial female. Morphological terms used below are shown on 
Fig. 1. 
In some cases I use a cluster analysis and diagrams of characters 
for differentiation between closely related species. Four metric 
characters are used (Fig. 2): W/L — ratio between width of dorso- 
posterior valve prominence and body length, M/L — ratio between 
length of dorso-posterior valve prominence and body length, G/L — 
ratio between height of dorsal valve margin and body length, D/L — 
ratio between diameter of dorso-posterior valve prominence and 
body length. Body length (L) was measured with an ocular microm- 
eter. Other measurements were made by drawing the body outline of 
each specimen with the aid of the camera lucida and measuring the 
details with an ordinary rule. 
Statistical analysis employed the computer system ‘Statgraphics’. 
Two-dimensional diagrams of characters are used for the detection 
of morphological hiatus between closely related species. Each 
specimen of each series is represented as a point on a coordinate 
plane. Coordinates of the point are equal to measurements of the 
specimen. Each series or group of series is represented with the 
polygon including the points corresponding to all specimens. If the 
polygons of two series/ groups of series do not overlap, there is a 

Fig. 2 Measurements of valves. G — height of dorsal valve margin, W — 
width of dorso-posterior valve angle, D — diameter of dorso-posterior 
valve angle, M — length of dorso-posterior valve angle. 
3 
morphological hiatus between them. I also use four-dimensional 
cluster analysis (average method) to determine which series are 
close to each other. Diagrams of characters and cluster analysis are 
independent of each other, because the former operates only with 
extreme values, the latter only with average values of characters. 
Therefore, if both methods give the same result, it is reliable. 
MORPHOLOGY 
Female 
Valves 
Maximum height of valves posterior to the middle. (Figs 1; 3B,C). 
Posterior margin (Fig. l:pvym) oblique, almost straight. Point of 
divergence of valves (Fig. I:dv) dorsal to dorso-posterior angle 
(Fig. |:dpva). Dorsal, posterior and ventral margins with denticles 
or smooth. Denticles arranged in 2 rows on dorsal margin (Fig. 
I:dd). Inner valve surface with a row of plumose setae on ventral 
margin (Fig. 1:ps), a row of setules groups on posterior margin (Fig. 
l:s) and 2-5 plumose denticles near ventro-posterior angle (Fig. 
I:d). Parthenogenetic female with 1-30 eggs in brood pouch. 
Ephippium containing | egg (Fig. 3C). 
Reticulation 
Valves and head reticulated. Reticulation consists of oblique stripes 
somewhat intersecting in mostof carapace and head and of polygons 
along valve margin and in front of eye. 
Head 
Comparatively small, noticeably delimited by depression on dorsal 
side (Fig. 1:dh). Rostrum always pointed, long or moderate. Frons 
(Fig. 1:fr) rounded, pointed or right-angled, with denticles or devoid 
of them. Ventral head margin (Fig. 1:vhm) with depression, deep or 
shallow, near rostrum. Fornices very broad (Figs 4; 5; 1:f). Posterior 
part of head with 3 main connected head pores, transversally orien- 
tated (Fig. 5, HP) and 2 minute lateral head pores seen only with 
scanning electron microscope, or without head pores. Eye and 
ocellus always present. 
Appendages 
Antennule tubular (Figs 6C), having 9 aesthetes at end and | sensory 
papilla proximally. Mandibles, maxillule and labrum as shown in 
Figs 4, 6. Antenna (Fig. 7) comparatively short, ends of distal 
segments reach only middle of valves. Proximal part of basipod with 
2 setae (Fig. 7E), outer side of distal part with a seta (Fig. 7D), inner 
side of distal part with a spine (Fig. 7C). Contrary to the opinion of 
Manujlova (1964), the length of the distal seta does not differ in 
different species. Exopod of antenna of 4; endopod of 3 cylindrical 
segments. Second segment of exopod with a short spine, third with 
a seta, fourth with 3 setae, of which one shorter than others and 
curved (Fig. 7B). First and second endopod segment each with 1 
seta, third segment with 3 setae. Contrary to the opinion of Behning 
(1912) and Manujlova (1964) number of setae on each trunk limb 
does not differ in different species. Interspecific differences concern 
only the length of certain setae. The structure of trunk limbs (Figs 6; 
8-11) has been described in detail (Orlova-Bienkowskaja, 1993b). 
Postabdomen (Figs |:p; 12A,B) 
High, with anal bay (Fig. 1:ab), supra-anal angle (Fig. 1:sa) and 2 
rows of anal teeth (Fig. |:at). Distal anal teeth large, covered with 
setules. Proximal teeth small, smooth. Dorsal part with groups of 
