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Records of the Australian Museum (2009) Vol. 61 
in 2007, in wet summers, generally about once every 5-10 
years (A. Longbottom, pers. comm.). Their water is humic 
(40-150 NTU), fresh (conductivity 260-440 pS/cm), warm 
(21-28°C), and acid to slightly alkaline (pH 5.8-7.4). By 
early March 2007, all of the ponds sampled had declining 
senescent populations, or none at all. 
Etymology. The species name derives from the paradox 
presented upon first examination: it has a carapace resem¬ 
bling L. birchii and a body-form superficially resembling 
L. tatei, but it differs from these two species on detailed 
examination. 
Male. Carapace (Fig. 13A) 14.6 mm long by 9.9 mm deep, 
L:D ratio c. 1.5. Dorsal margin doubly curved so lowest point 
at anterior umbo area and highest point about two-thirds of 
way along the hinge line. Hinge line uneven with growth lines 
protruding as small carinae, these generally more prominent 
posteriorly. Umbo humped dorsoanteriorly. Growth lines 
12, expressed, crowded anteriorly, but more spaced spaced 
posteriorly. Carapace coloured dark humic brown. 
Head (Fig. 13B) with a pear-shaped pyriform frontal organ 
posteriorly, preceded by rounded prominence containing eye, 
then by large rostrum at right angles to head. Length of rostrum 
similar to length of anterior surface of head and about twice 
its own basal width. Rostrum curved downwards apically and 
containing triangular naupliar eye dipping at angle to rostrum 
axis and occupying much of its basal area. 
First antenna with 11 subequal lobes, slightly longer than 
peduncle of second antenna. Two flagella each bearing 15-18 
beaded flagellomeres, each of latter with up to 6-7 spines 
evenly spaced along dorsal surface. 
Trunk segments 26. Dorsally, posteriormost segment with 
spineless protuberance, preceding 7-8 segments each with 
3-5 spines on protuberance, then further anteriorly another 
7 segments with 5-9 long setae each. Hand of claspers with 
blunt narrow outgrowth near inner basal comer. Third tho- 
racopod (Fig. 4D) similar in structure to that of L. birchii. 
Proportions of endites, endopod, exopod and epipodite 
slightly different, and significantly palp of fifth endite slightly 
shorter than fifth endite and epipodite proportionally smaller. 
Other thoracopods of same basic stmcture, but without palp 
and with larger epipodite. 
Telson (Fig. 13C) with two rows of 13 to 14 strong, 
subequal spines, although the first spine slightly larger than 
next few spines and curving slightly posteriorly, middle 
spines slightly smaller and posterior spines more widely 
spaced, and sharper last spine near apex of claw. Two telsonic 
setae inserted on protuberance about one quarter of way 
along dorsal side of telson. Caudal claws well developed, 
at least twice as large as telsonic claws, curved concavely 
dorsally, with basal two-thirds bearing about 20 setae mes- 
odorsally and terminating in a spine. Apical third of claw 
with many fine denticles dorsally. 
Female. Carapace (Fig. 13E) 13.5 mm by 9.7 mm. Similar 
to that of male, but anterior concavity less pronounced and 
highest point of carapace at about midlength. Carinae of 
growthlines prominent, but blunt compared with those of 
male. 
Head (Fig. 13F) similar to that of male, but rostrum short, 
about as long as deep, and blunt. Naupliar eye of about same 
size and position as in male, thus occupying much of rostmm. 
First antenna shorter than in male, with about 8 lobes. Second 
antenna as in male. 
Number of body segments, and details of telson (Fig. 
13G) similar to those in male. 
Eggs (Figs. 4L,M) top-shaped, with prominences dorsal 
and ventral and about 5 prominences around equator. 
Typically about 16 grooves between equator and dorsal 
and ventral prominences, and about 3-4 grooves between 
each equatorial prominence. Ridges between grooves may 
be straightish or Y-shaped, the latter generally in the fields 
between equatorial and dorsal or ventral grooves. Sometimes 
only 4 equatorial prominences present and grooves somewhat 
randomly distributed. Maximum dimensions about 250 pm 
(range 241-254 pm, n = 20). 
Variability. The carapace size varies from c. 13 to 16 mm, 
growth lines from 10 to 14, first antennal lobes 9 to 11, 
telsonic spines 15 to 18, and caudal claw setae from 16 to 
21. There is no significant variation in the characteristic 
carapace shape, and all specimens have just one spine on 
the caudal claws. 
Comments. Limnadopsis paradoxa resembles small 
specimens of L. birchii, on account of its size, general 
shape, development of the carinae, and perhaps colouration. 
However, the body inside bears absolutely no resemblance to 
that of L. birchii. For instance there are 26 body segments, 
not 32, and there are only c. 14 telsonic spines on a almost 
straight edge compared to c. 50 spines on a doubly curved 
edge. The new species is most like L. tatei but has more 
growth lines, more lobes on the first antenna, more telsonic 
spines and more setae on the caudal claws. Perhaps it could 
be regarded as a bigger form of L. tatei, but the shape of 
the carapace is distinctive, particularly the concave dorsal 
surface and the lateral development of the umbo. The smaller 
first: second telsonic spine size ratio in L. paradoxa, and more 
numerous caudal claw setae are also distinctive. Limnadopsis 
pilbarensis n.sp. (see below) differs by having a convex edge 
in the umbo area, much less pronounced development of the 
dorsal outgrowths of the growth lines, and fewer telsonic 
denticles and setae on the caudal claws. 
The eggs of L. paradoxa and the three other above- 
mentioned species are distinctive among themselves. At 40x 
magnification, eggs of L. birchii and L. tatei are smoothly 
round with groups of parallel grooves, more of the latter in 
L. birchii than in L. tatei. Eggs of L. paradoxa and L. pilba¬ 
rensis both have rough surfaces, but those of L. pilbarensis 
have many (> 20) spines and those of L. paradoxa have just 
a few (<8) rounded prominences. These distinctions are even 
more pronounced as observed by SEM (Fig. 4). 
