Lynceus susanneae, Timms, 2013

TIMMS, BRIAN V, 2013, A Revision of the Australian species of Lynceus Müller, 1776 (Crustacea: Branchiopoda: Laevicaudata, Lynceidae), Zootaxa 3702 (6), pp. 501-533 : 524-527

publication ID	https://doi.org/ 10.11646/zootaxa.3702.6.1
publication LSID	lsid:zoobank.org:pub:A875F2FF-3DAA-4AC3-9451-773F095A7C82
persistent identifier	https://treatment.plazi.org/id/346D87FD-F129-254D-2A90-4ACCFD688252
treatment provided by	Felipe
scientific name	Lynceus susanneae
status	sp. nov.

Treatment

L. susanneae View in CoL sp. nov.

( Fig. 3F View FIGURE 3 , 4F View FIGURE 4 , 13 View FIGURE 13 )

Etymology. This species is named to honour Mrs Susanne McGrath, wife of the manager of Balladonia Station on the western edge of the Nullarbor Plain, where this species occurs. Susanne and husband Alan have hosted my numerous visits and moreover have taken a keen interest in the shrimps of rockholes.

Type Locality: Western Australia, Nullarbor Plain, Cocklebiddy , ca 32 o 02’S, 126 o 06’E, 29 May 1954, no collector recorded GoogleMaps .

Hototype: Male deposited in Western Australian Museum, Perth. Length 5.8 mm, height 4.2 mm. Registration number WAM 51613.

Allotype. Female deposited in Western Australian Museum, Perth. Length 5.5 mm, height 4.1 mm Registration number WAM 51614.

Paratypes. 2 males, 2 females, Western Australia, Nullarbor Plain, Cocklebiddy , ca 32 o 02’E, 126 o 06’E, 29 May 1954, no collector recorded, WAM 51615 , 2 males, 2 females, Western Australia, Nullarbor Plain, Cocklebiddy , ca 32 o 02’E, 126 o 06’E, 29 May 1954, no collector recorded AM P90027 .

Other Material. Western Australia. Nullarbor Plain , 48 km NE of Mundrabilla Homestead, June 1964, Mr Lee, AM P55656 , AM P88154 ; Nullarbor Plain, Mundrabilla , 32.3 km W, ca 31 o 49’S, 127 o 53’E, 15 May 1966, J. Lowry, WAM 51327 GoogleMaps ; Madura , ca 31 o 54’S, 127 o 01’E, 24 December 1966, J. Lowry, WAM 14296 GoogleMaps ; Nullarbor Plain, Burnablat, Nooraira Run , but possibly Burnabbie Homestead , 70 km W of Madura, 2 October 1966, J. Lowry, WAM C51330 ; Nullarbor Plain, Cocklebiddy , ca 32 o 02’E, 126 o 06’E, 29 May 1954, no collector, WAM 51326 ; Nullarbor Plain , 12 km S of Cocklebiddy, 32 o 08’ 14”S, 126 o 04’ 51”E, 4 August 2004, A. Clarke, stored in DEC’s collection GoogleMaps ; Nullarbor Plain, Cologna Rockhole , 32 o 03’E, 126 o 31’S, 6 August 2004, A. Clarke, stored in DEC’s collection .

Diagnosis. Endite of male thoracopod I with digitiform process with parallel margins and concave underneath and reaching about half way along the medial surface of endite III and part way along the row of spines on endite III. Truncated male rostrum at an angle of near 90 o to rostral axis and rostral carina weakly developed. Female with lateral abdominal process with at least three foliaceous lobes and no digital lobe and with a long pocket basally.

Description of male: Head ( Fig. 13B,C View FIGURE 13 ) a little smaller than body. Fornices angulate and weakly arcuate over second antennal base. Posterior fornices a little wider than widest part of head near the eyes. Small mound centroposteriorly, the site of the dorsal organ. Compound eyes close together about three-fifths along central ridge and just posterior to the frontal pore and two lateral setal fields. Suture and ridge anterior to these fields strongly developed, so that fields lie in a transverse hollow. Ocellus deeply embedded beneath the setal fields. Rostrum slightly longer than wide with lateral margins weakly arcuate but widening distally with distal margins almost parallel. No central carina on rostrum. Rostrum truncated at almost 90 o to linear axis and with dorsal margin unsclerotised and strongly arcuate and ventral margin weakly arcuate and ciliated. Head bent anteriorly from linear axis by about 30 o.

First antenna ( Fig. 13D View FIGURE 13 ) a little longer than rostrum and with two antennomeres. Proximal antennomere cylindrical and distal antennomere clavate, a little longer than proximal antennomere and bearing a few setae dorsally and apically.

Second antenna ( Fig. 13E View FIGURE 13 ) biramous, well developed and protruding about a third of its length beyond the rostrum. Peduncle of three segments, proximal segments with 3–4 setae, middle segments with 1–2 spines and distal peduncular segment with about 10 spines mostly shorter than the antennomere. Anterior (dorsal) ramus with about 38 antennomeres and ventral ramus with a couple more. Both rami with plumose ventral setae, one per antennomere and dorsal ramus with dorsal spines as well, crowded proximally and often in different planes but distally more ordered and in one plane; sometimes 2 per antennomere.

Labrum large, well developed, clothed in small setae. Mandible broadly spatulate. First maxilla typical for genus and second maxilla absent.

Carapace ( Fig 13A View FIGURE 13 ). Umbo absent and abductor muscle scar in an anteriolateral position about twice its diameter from the margin and associated with oval imprint of maxillary glands lying at about 30 o to the hinge line. Hinge line straight and sloping posteriorly so that anterior of carapace broadly arcuate and posterior sharply arcuate; anterior half distinctly higher than posterior half. Valves rounded and inflated laterally.

Thorax. Ten thoracic segments, each with a pair of thoracopods. Anal plate ( Fig. 13H View FIGURE 13 ) undivided but with a concave indentation medioposteriorly. Each apex bearing a long seta. Somite below divided and with apices rounded.

Thoracopod I. ( Fig 3F View FIGURE 3 , 13F,G View FIGURE 13 ) modified as a clasping appendage, right and left claspers equal in size and shape. Endite VI with a broad base attached to endite III, evenly curved dorsally and with a digitiform process a little longer than its base line attachment to endite III. Finger undersurface concave and margins parallel. Apex rounded and reaching about half way along the row of spines on endite III. Endite V two to three times longer than wide, pyriform with a narrow apex and irregularly clothed with many setae including a vertical row of about ten stout setae, and a field of numerous dishevelled setae nearby. Endite IV asymmetrically shaped with the margin adjacent to endite V gently curving and with few setae, while opposite margin distinctly curved and clothed with many long setae. Endite III rectangular but with median margin arcuate. Distiomedial corner with a row of about ten triangular spines; these spines uniform in size, but spacing a little irregular. Mediolateral face with numerous stout setae, longest and most crowded in distiomedial corner.

Description of female. Head ( Fig. 13J,K View FIGURE 13 ). General structure similar to male. Compound eye, frontal pore and setal fields as in male. Anterior dorsal carina weak, rostrum almost twice as long than wide and anterior margin evenly arcuate. Head axis from cervical suture to rostrum slightly curved (<30 o). Both antennae of similar structure to male, but antenna 1 not protruding, and antenna 2 less protruding as rostrum is not truncated in female.

Carapace: as in male, umbo lacking,same shape and size. Egg mass, if present visible through the carapace.

Thorax. Twelve trunk segments, the last three with a lamina abdominalis on each side ( Fig. 11L), with variable lobes on each side, anterior, medial and lateral lobes discernable, bases of all conjoined to form a long sac by far the most prominent feature of the lamina. No digital lobe anteriorly.

Thoracopods. Twelve pairs of thoracopods, IX and X with exopod dorsal lobes cylindrical and extending dorsally beyond thoracic dorsum. These help to anchor the egg mass. Last five thoracopods much reduced without an epipodite and proximal exopodite.

Resting egg ( Fig 4F View FIGURE 4 ). Round, irregular low wide ridges enclosing enlongated irregular depressions. Diameter 112.7 ± 2.9 ųm (n = 5).

Size. Holotype 5.8 long x 4.2 mm high; male paratypes 5.7 x 4.8 mm, 5.4 x 4.9mm, 5.1 x 4.0 mm, 5.0 x 4.1mm. Allotype 5.5 mm long and 4.1 mm high; female paratypes 5.4 x 4.4mm, 5.1 x 4.4 mm, 5.2 x 4.3 mm, 5.2 x 4.1 mm.

Variability. As in all Australian Lynceus , many features vary between individuals and populations. The digitiform process of endite VI may not always have parallel margins, but in all specimens seen, it was concave ventrally. It variously reaches one third to one half along the spine row, which itself varies in number from seven to ten generally triangular spines, but sometimes more rectangular in shape. Endite V is generally pyriform shaped, but the setae are variable, so that particularly the row of stout setae can vary from eight to 15 setae and extend further from the apex than in the types. While setae and spines of the antennal peduncle vary a little, the dorsal spination of the anterior ramus is widely variable in detail, but generally the spines are crowded basally and more regular apically and often there is duplication in some antennomeres. These features make the second antenna of L. susanneae distinctive among the six species of Australian Lynceus .

In females, as well as this variation in second antenna spination, the laminae abdominalis are particularly variable in their lobation, but the presence of a well defined basal pocket is always obvious.

Distribution. Lynceus susanneae sp. nov. is known only from a few rockholes in limestone (e.g. Fig. 9D View FIGURE 9 ) on the western Nullarbor Plain of Western Australia.