Lynceus baylyi, 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 : 516-520

publication ID	https://doi.org/ 10.11646/zootaxa.3702.6.1
publication LSID	lsid:zoobank.org:pub:A875F2FF-3DAA-4AC3-9451-773F095A7C82
DOI	https://doi.org/10.5281/zenodo.5463049
persistent identifier	https://treatment.plazi.org/id/346D87FD-F131-2544-2A90-4827FB6A8176
treatment provided by	Felipe
scientific name	Lynceus baylyi
status	sp. nov.

Treatment

Lynceus baylyi View in CoL sp.nov.

( Figs. 4D View FIGURE 4 , 6A,B,E,F View FIGURE 6 , 10 View FIGURE 10 , 11)

Etymology. This species is named for Dr Ian A. E. Bayly, limnological pioneer and an early student of gnammas (rockholes). It is particularly fitting this species should honour him as it occurs mainly in gnammas in the arid inland of Western Australia, the site of many recent expeditions by Ian in a quest to understand the early white explorers and track makers of this remote part of Australia and to study its gnammas (see Bayly 2009; Bayly et al. 2011).

Type locality. Australia, Western Australia, 14.6 km NNE of Trayning , middle gnamma of five in a row, 30 o 59’ 29”S, 117 o 50’ 47”E, 20 October 2011, collector BVT GoogleMaps .

Holotype. Male deposited in the Western Australian Museum (Perth). Length 6.9 mm. Registration number WAM 51627.

Allotype. Female deposited in the Western Australian Museum (Perth). Length 6.9 mm. Registration number, WAM 51628.

Paratypes. 8 altogether; 2 males and 2 females deposited in Australian Museum (Sydney). Accession number, AM P89064 , and 2 males and two females deposited in Western Australian Museum (Perth) WAM 51629 .

Other Material. South Australia: Muckera Rockhole, N of Cook, SAM C7628.

Western Australia: 140 km NW of Warburton , rockhole Bakers Range, 20, June, 1979, J. Blyth, WAM 51571 ; gnamma 1.6 km WSW of Mt Samuel , AM P55688 ; Great Victoria Desert, David Carnegie Rd, Pikalu Rockholes , 26 o 54.795’S, 124 o 27.505’E, 4 September, 2010, IAEB, WAM 51572 GoogleMaps ; Great Victoria Desert, Great Central Rd near Tjukayirla Roadhouse , Tugaila Rockhole , 27 o 09.355’S, 124 o 34.378’E, 3 September 2010, IAEB, WAM 51573 GoogleMaps ; Great Victoria Desert, Ryans Bluff , gnamma on top, 27 o 14’ 04”S, 126 o 26’ 34”E, 16 May 1968, A.G. Matthews, WAM 51320 GoogleMaps ; Great Victoria Desert, Great Central Rd, Eurothurra Rockhole , 5 September, 2010, IAEB, WAM 51574 ; Great Victoria Desert, Saunders Range North Rockhole , 27 o 49.693’S, 125 o 37.453’E, 29 August 2010, IAEB, WAM 51575 GoogleMaps ; Great Victoria Desert, Point Saunders Waterhole , 27 o 50.865’S, 125 o 38.356’E, 30 August, 2010, IAEB, WAM 51576 GoogleMaps ; Great Victoria Desert, Amy Waterhole , 27 o 52.097’S, 125 o 18.553’E, 27 August 2010, IAEB, WAM 51577 GoogleMaps ; Great Victoria Desert, Hanns Lily Rockhole , 28 o 00.281’S, 124 o 44.832’E, 26 August 2010, IAEB, WAM 51578 GoogleMaps ; Great Victoria Desert, Point Sunday Rd, Point Sunday Rockhole , 28 o 07.433’S, 124 o 03.077’E, 24 August 2010, IAEB, WAM 51579 GoogleMaps ; Great Victoria Desert, Bartletts Bluff Rock Hole , 29 o 04.900’S, 124 o 36.615’E, 6 July 2010, Ian Elliot, WAM 51580 GoogleMaps ; Leinster, 56 km N, Kathleen Valley ( Wanjarri ), ca 27 o 24’S, 120 o 38’E, pre 1978, J. Moriaty, WAM 51325 GoogleMaps ; Laverton, 64 km SSE, Mt East , gnamma, 28 o 58’ 16”S, 122 o 39’ 21”E, August 1963, G. Hutchin, WAM 51315 GoogleMaps ; Beacon, 40 km NW, Washington Rocks , 30 o 09’ 06”S, 117 o 34’ 41’E, 4 August 2012, BVT, WAM 51581 ; Beacon, 14 km NNW, Yellari Gnamma , 30 o 19’ 44”S, 117 o 49’ 58”E, 29 August 2009, BVT, WAM 51581 GoogleMaps : Bencubbin, 3 km N, northmost pit gnamma on Cadigan , 30 o 46’ 53”S, 117 o 52’22”E, 5 August 2012, BVT, WAM 51583 GoogleMaps .

Diagnosis. Endite VI of thoracopod I with a broad base, evenly curved and with a long and thin digitiform process, a little longer than the basal width and tapering apically to a rounded tip. The digitiform process reaches about three quarters along medial surface of endite III, completely covering the spines at its distomedial surface. Truncated male rostrum at an angle of about 45 o to rostral axis.

Description of male. Head ( Figs. 6A View FIGURE 6 , 10B,C View FIGURE 10 ): subequal to body size, finely punctuate. Fornices broad, angulated and arcuate over second antennal base. Small mound centroposteriorly, the site of the dorsal organ. Compound eyes close together about midway along the central ridge and just posterior to the frontal pore and two small lateral setal fields. Ocellus deeply embedded beneath the setal fields. Rostrum about as long as wide with lateral margin slightly expanded distally and with these margins slightly divergent. Lateral suture between compound eye and lateral fornix dividing a slightly elevated posterior head from a slightly depressed posterior rostrum. Central carina a sharp ridge bifurcating distally associated with terminal truncation to form a broadly based and sloping triangular facet. Ventral margin of triangular base slightly arcuate and ciliated. Head bent anteriorly from plane of compound eye/dorsal organ to rostrum by about 30 o and triangular truncated facet sloping at about 45 o from plane of rostrum.

First antenna ( Fig 10D View FIGURE 10 ) small much shorter than rostrum and with two antennomeres. Proximal antennomere cylindrical and distal antennomere clavate, about 2.5 times length of proximal antennomere, and bearing, mainly dorsally, numerous papillae.

Second antennae ( Fig 10E View FIGURE 10 ) biramous, well developed, twice as long as rostrum. Peduncle of three segments; proximal segment with three to four plumose setae, second segment with 1one to two spines and distal peduncular segment with about 14 short spines anteriorly against the first antennomere of anterior ramus. Anterior ramus of about 35 antennomeres and ventral ramus with a few more antennomeres. Both rami with long plumose ventral setae, one per antennomere, while anterior ramus with short dorsal setae also, almost always one per antennomere.

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

Carapace ( Fig. 10A View FIGURE 10 ): with hinge line straight, umbo and growth lines lacking. Anterior margin broadly arcuate, curving evenly to ventral margin and back to the posterior, though posterior slightly narrower so that deepest part of carapace a little before midway along its length. Dorsally carapace slightly arcuate, thus hiding the hinge line. Valves roundly inflated laterally. Carapace surface finely punctate. 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 40 o to the hinge line.

Thorax. Ten thoracic segments, each with a pair of thoracopods. Anal plate ( Fig. 10K View FIGURE 10 ) partly divided centroposteriorly, each half bearing long seta apically. Somite below enlarged, similarly divided with each half bearing a small denticle apically.

Thoracopod I modified as a clasping appendage, right and left claspers equal in shape and size ( Fig 3D View FIGURE 3 , 6B View FIGURE 6 , 10F View FIGURE 10 ). Endite VI with a broad base, evenly curved and with a long thin digitiform process, a little longer than the basal width and tapering apically to a rounded tip. This digitiform process closely appressed to endite III and reaching well beyond the latter’s spine row, to about two-thirds along the medial surface of endite III. Endite V three to four times larger than endite IV, subcylindrical and gently curved, and irregularly clothed in long setae, one series of about 15 stouter setae in a defined curved row extending from about one third way along the endite to almost the apex and the other setal series thinner and in a oval field somewhat dishevelled adjacent to the row. Endite IV asymmetrically shaped with margin adjacent to endite V gently curving and with few setae, while the opposite margin distinctly curved and clothed with many long setae. Endite III rectangular in lateral view though narrowing slightly distally and with longest axis aligned parallel to axis of thoracopod. Distomedial corner with a row of about eight triangular spines of various sizes. Mediolateral face with numerous stout setae mainly distributed marginally on the face but crowded in distomedial corner.

Thoracopod II ( Fig. 11) of typical general form with 5 endites medially, an exopod with dorsal and ventral lobes and an epipodite (Martin and Belk 1988). Endite I (= endite of praecoxa, Ferrari and Grygier 2012), subcylindrical with many short setae on distal (medial) surface and many long closely spaced setae on proximal margin and terminating in two teeth, each with two rows of denticles. Endites II and III rectangular, endite II about 50% longer than endite III, both with numerous shorter anterior setae and longer posterior setae. About 20 of the former on endite II with serrated margins on distal half, other anterior setae naked and located mainly on proximal and distal portion of Endite II and all along Endite III. Posterior setae of endites II and III plumose but lateral setules short. Endites IV, V and endopod digitiform with rounded apices and numerous long plumose setae similar to the posterior setae of endites II and II on their basal margins. A few pectinate setae near their apices. Palp without a hook apically.Ventral (i.e. distal) lobe of exopod lanceolate but widest just beyond its base and margined with long plumose setae distally and shorter plumose setae basally. Dorsal (i.e. proximal) lobe of exopod foliate and margined with short plumose setae except at its medodistal corner with its many longer setae. All these plumose setae with long setules. Epipod subcylindrical with a rounded apex and naked margins.

Thoracopods III to XI similar to thoracopod II, though the last three much reduced in size and lacking epipodites and proximal lobe of the exopodites.

Description of female. Head ( Fig 10I, J View FIGURE 10 ): general structure similar to male. Anterior dorsal carina not bifurcated and rostrum not truncated, so that rostrum a little longer than wide. Anterior margin of rostrum arcuate, projecting medially. Head axis from cervical suture to rostrum slightly curved (<30 o).

Carapace: ( Fig 10H View FIGURE 10 ) as in male, umbo lacking. Same size and shape. Egg mass, if present, visible through the carapace.

Thorax: Twelve thoracic segments, the last three with a lamella abdominalis consisting of a digitiform process anteriomedially, three spaced and long digitiform processes laterally and a obtuse lobe posteriorly ( Fig. 6E F View FIGURE 6 , 10K View FIGURE 10 ). Anal plate as in the male, but last somite, though with a pointed apex, generally more rounded than in male ( Fig. 10K View FIGURE 10 ).

Thoracopods: 12 pairs of thoracopods, 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. 4D View FIGURE 4 ) Round, irregular low wide ridges enclosing enlongated irregular depressions. Size 141.2 ± 3.4 ųm (n = 5).

Size. Length holotype 6.9 mm, paratypes (n=4) 6.6 – 7.0 (x = 6.85 ± 0.17 mm); height holotype 5.5 mm, paratypes (n=4) 5.8 – 6.0 (x = 5.9 ± 0.08 mm), width holotype 4.8 mm. Length allotype 6.9 mm, paratypes (n=4) 6.1 – 7.0 (x = 6.62 ± 0.36 mm), height allotype 5.5 mm, paratypes (n=4) 5.1 – 5.7 (x = 5.47 ± 0.33 mm), width allotype 5.0 mm.

Variabilty. The male rostral terminal facet may slope at angles greater up to 60 o rather than about 45 o. The first antenna can be shorter than the rostrum, but always the distal antennomere is longer than the proximal antennomere. Likewise the second antenna is not always twice the length of the rostrum, but can be as short as 1.5 x the rostrum length, but in adults at least, the number of antennomeres always approximate 35. There may however be as few as eight setae on the third antennomere of the peduncle (instead of up to 14), and the basal peduncle antennomere can bear as many as 7 plumose setae. On the clasper, the digitiform process of endite VI may be much longer than its basal width, the palps variable in shape and setation, and the teeth on the medioposterior corner of endite III can number 6 to 9.

In females the rostral apex may be notched at the anteriolateral corner and the lobes on the posteriolateral plate can vary in proportions and shape, though there are always two anteriodorsal digitiform processes. The lamella abdominalis presents differently in different individuals, probably because the posterior lobe sometimes is tucked under main lamina to form an efficient structure for holding eggs. The digitiform process can vary from triangular to digitiform in shape, and occasionally there are two rather than a single anteriomedial digitiform process.

Distribution and Ecology. Lynceus baylyi sp. nov. occurs most reliably in gnammas (rockholes) in the remote central inland (Great Victoria and Gibson Deserts) of Western Australia. There are also a few records in pit gnammas curiously arranged in a line south of Paynes Find (Washington Rocks) to Beacon (Yellari Rocks) to Bencubbin (Cadigan Rock) to Trayning (the five pit gnammas 14 km north of town, Fig. 9B View FIGURE 9 ), perhaps indicating some past directional dispersal. Interestingly this could give some credence to an aboriginal legend concerning the mythical Nyimgarn, the Echnida, which came down from Ninghan Station (west of Paynes Find) to Trayning and dug out the five pits there with his snout. There is also an extension in distribution across to the northern Nullarbor in South Australia and the likelihood of occurrences in the Pitjantjatjara Lands of northwestern South Australia, given similar environment to that in the Great Victoria Desert.

It is a long lived species, thought to live for at least 6–9 months (author, unpublished data) and is the largest Lynceus in Australia, growing to about 7 mm. It is invariably found in deeper gnammas, these generally being pipe gnammas in laterite or pit gnammas in granite (see Bayly et al. 2012; author unpublished data).