A Revision of the Australian Endemic Clam Shrimp Genus Limnadopsis Spencer & Hall (Crustacea: Branchiopoda: Spinicaudata: Limnadiidae) Timms, Brian V. Records of the Australian Museum 2009 2009-05-27 61 1 49 72 b05c40f1-fdd6-487a-9ec2-535ea67bf03f Timms, 2009 Timms 2009 [963,1275,815,841] Branchiopoda Limnadiidae Limnadopsis GBIF Animalia Diplostraca 14 63 Arthropoda species occidentalis sp. nov.   Figs. 2F, 5J, 12  Types.  Holotype3 WAMC39336, allotype ♀ WAMC39337, paratypes, 23, 2♀, WAMC39338. Type locality: Western Australia, N of Carnarvon, Boolathana Station, unnamed claypan, 24°38'34"S 113°59'35"E,  15.iii.1995, S.A. Halse.   Other material:   Western Australia: 23, 8♀, 58.6 kmsouth of Roebourne, small pools adjacent to creek, 20°48'S 117° 6'E,  25.vi.1964, C. Pugh, AMP55651;  13, 131 milepost, road to Port Headlandvia Woodstock, waterhole, 21°12'S 118°48'E,  26.vi.1964, C. Pugh, AMP55650; 63,  2♀, E of Kalbarri, Coolcalalaya Station, unnamed clay pan, 27°31'29"S 115°05'14"E, S.A. Halse,  15.iii.1995, WAMC39339; c. 40 kmsouth of Mullewa, Tardan, Christian Brothers College, dam, 28°43'S 115°49'E,  25.vii.1999, J. McRae& A. Pinder, DEC, Woodvale, SPS185;  1♀, via Laverton, 20 kmwest near highway, samphire swamp, 28°36'S 122°13'E,  17.ii.2003, B. Datson, WAMC39340.  Habitat and distribution.  Limnadopsis occidentalislives in a variety of temporary fresh waters, including claypans and floodplain pools, all in northwestern Western Australia.   Etymology. The species name is derived from the Latin occidensreferring to the direction of the setting sun, and hence “west” an appropriate epithet for a species found in the west of Australiaas opposed to its closely related species  L. parvispinus, which is found in eastern Australia.  Male. Carapace ( Fig. 12A) oval, 11 mmby 6 mm, L:D ratio = 1.8. Dorsal margin weakly convex with highest point at about one-third length, slight depression anterior to umbo and distinct dorsoposterior angle. Dorsal margin almost smooth, but with slight serrations at many growth lines, mainly posteriorly. Growth lines 11, weakly expressed. Carapace weakly granulated within, but presenting a smooth yellow-buff surface in preserved condition. Head ( Fig. 12B) with pyriform organ posterior to eye mound and about as high as latter. Anterior sides of eye mound and rostrum both straight and meeting at a distinct angle of about 110°. Rostrum elongated triangular, about as long as anterior surface of head, apex rounded and slightly flexed downward. Naupliar eye triangular, its axis aligned similarly to that of rostrum. Length of first antenna subequal to that of peduncle of second antenna, and former bearing 7 lobules. Second antenna with 12 apparent peduncular segments and 15–16 flagellomeres on flagella, most middle segments with 5–7 spines, 2 of which sometimes grouped apically. Trunk segments 25 innumber, each bearing pair of thoracopods, these decreasing in size posteriorly, and anterior two pairs modified as claspers. Posterior dorsal armature comprising 1–3 spines on small protuberances on each of last 7 segments, and a few setae on preceding 6 segments. Claspers of normal structure for  Limnadopsis, with one spine apically on the movable finger, and prominent, asymmetrical protrusion midway along anterior edge of hand. Telson ( Fig. 12C) with two rows of 13 dorsal spines each. Most anterior spine about 1.5 times the size of next spine, most posterior spines smaller and sharper than anterior spines, and spines in middle of row more widely spaced than anterior or posterior spines. Two telsonic setae inserted on protuberance situated about one quarter of way along dorsal side of telson. Caudal claws about 8 times longer than wide, with long, almost straight basal section of even width and much shorter, curved apical part tapering to a sharp apex. Basally, cercopods bearing about 12 setae mediodorsally, most of them being a little longer than width of claw, followed by 3 short spines inserted almost dorsally, the posteriormost the largest. Curved, tapered apical part of cercopods bearing many short denticles dorsally.  Female. Carapace ( Fig. 12D) oval, 11 mmby 7 mm, L:D ratio 1.57. Dorsal margin more convex than in male and also with distinct depression in umbo area. Dorsal margin largely smooth, but minor serrations present posteriorly at junctions of growth lines. Growth lines 9, weakly expressed. Head ( Fig. 12E) typical for females of  Limnadopsis, with short triangular rostrum. Six lobules on first antenna. Second antenna as in male. Telson ( Fig. 12F) similar to that of male, but with 15 telsonic spines in each row, and six spines on caudal claws. Eggs ( Fig. 5J) round, about 175 µm in diameter (range 170–178 µm; n = 5) with short deep grooves, aligned at most in pairs, otherwise set at various angles to one another. Intergroove areas smooth and internally frothy.  Variability. Considerable variability was noted in representatives of the six populations studied. Growth lines vary from 9 to12, but they are invariably weakly expressed and meet the dorsal margin in at most weak dorsal serrations posteriorly. First antennal lobules vary from 6 to 9, with males of a given population generally having one more than females. On the telson, the dorsal spines vary from 12 to16 per row, with a mean of 13; and the spines on the caudal claws range from 2 to 6, usually about 4.   Comments. This species is similar to  L. parvispinus. Despite wide variation in many features of both species, there are many differences between the two, including: ( a) fewer telsonic spines in  L. occidentalis(about 13–15 per row compared to about 18–22); ( b) A slight anterior depression in the dorsal carapace margin of  L. occidentaliswhile in  L. parvispinusthe margin is straight or slightly convex; ( c) the differently shaped eggs, round in  L. occidentalisand with the grooves ungrouped or at most in pairs, compared to cylindrical to muffin-shaped in  L. parvispinuswith multiple parallel grooves in the outer cortex; ( d) most flagellomeres have six dorsal spines in  L. parvispinus, but five in  L. occidentalis; ( e) fewer setae and fewer spines on the caudal claws in  L. occidentalis(ca 12 setae in  L. occidentalisand c. 15 in  L. parvispinus; 2–6 spines in  L. occidentalisand 4–9 spines in  L. parvispinus); and ( f) usually one fewer lobule in the first antenna in  L. occidentalis(6–9, verses 7–10 in  L. parvispinus). C39336, C39337, C39338 1995-03-15 WAM S. A. Halse. -24.642778 Boolathana Station 21 113.99305 Carnarvon 14 63 3 3 Western Australia holotype P55651 1964-06-25 AM C. Pugh -20.8 Roebourne 1266 117.1 14 63 8 8 Western Australia P55650 1964-06-26 AM C. Pugh -21.2 Woodstock 1264 118.8 Port Headland 14 63 1 Western Australia C39339 1995-03-15 WAM S. A. Halse -27.524721 Coolcalalaya Station 20 115.08723 Kalbarri 14 63 2 2 Western Australia 1999-07-25 J. McRae & A. Pinder & Woodvale Mullewa -28.716667 Christian Brothers College 1230 115.816666 Tardan 14 63 1 Western Australia C39340 2003-02-17 WAM B. Datson -28.6 Laverton 1231 122.21667 14 63 1 1 Western Australia