Larinia tumulus Framenau & Castanheira 2022, n. sp.

Larinia tumulus n. sp.

Figs 4–7.

Type material. Male holotype from Barrow Island (20°47’08.718”S, 115°27’26.904”E, Western Australia, AUSTRALIA), N. Gunawardene, 27 September 2015, suction sample (WAM T153634).

Other material examined. AUSTRALIA: Western Australia: 1 female, Barrow Island, 20°41’34.962”S, 115°25’07.854”E, N. Gunawardene, 26 September 2015, litter sample (WAM T153635; 1 female, Barrow Island, 20°49’31.884”S, 115°26’38.958”E, M. Hamilton, 17 November 2017, window trap (HBI N5134-1); 1 male, Barrow Island, 20°47’59”S, 115°27’00”E, S. Callan, 15 March 2006, suction sample, low limestone ridge (WAM T 99446); 1 female, Barrow Island, 20°47’12”S, 115°27’17”E, 24 April 2005, S. Callan, night hand collecting (WAM T 99447); 1 male, Barrow Island, WAPET Camp, 20°49’43”S, 115°26’40”E, M.S. Harvey, J. M. Waldock, 5 November–3 December 1993 (WAM T 57659).

Etymology. The specific epithet is a masculine noun in apposition derived from the Latin word for barrow (tumulus), referring to the type locality, Barrow Island.

Diagnosis. Larinia tumulus n. sp. is by far the smallest Larinia species in Australia (Fig. 3A, B) (body length males <3 mm, females <4 mm; all other species: males> 4 mm, females> 5 mm (Framenau & Scharff 2008)). The median apophysis of the male pedipalp is unique amongst Australian species with two spine-like dorsal prongs (Figs 4C, 6A); most similar is L. sexta n. sp. but the prongs in that species are much stronger (Figs 1C, 3A). Similarly, the large, ovoid, flat epigynum is unique amongst Australian Larinia, that of L. sexta n. sp. has a much more pronounced median septum (Figs 2C, 3D, 4C, 6D).

Description

Male (holotype).

Total length 2.57. Carapace (Fig. 4A): 1.02 long, 0.81 wide; yellow-brown, light brown with dark olive-green median band that is forked into three at margin of cephalic area; lateral margins dark olive-green. Eyes: AME 0.13, ALE 0.07, PME 0.11, PLE 0.07; row of eyes: AME 0.34, PME 0.23, PLE 0.50. Sternum (Fig. 4B): 0.50 long, 0.40 wide; yellow with irregular olive-green margin. Labium (Fig. 4B): wider than long; basal half with olive-green pigmentation, anterior part forms a nearly semi-circular whitish rim. Chelicerae (Fig. 4B): yellow; promarginal and retromarginal teeth not counted to avoid major damage of the very small spider.

Pedipalp (Figs. 4C, D, 6A, B): conductor finger-like with rounded, sclerotised tip; embolus slightly arched with pointed tip and longer than tegulum border; tegulum with small pointed lobe; median apophysis kidney-shaped, with two prongs of different sizes, the basal longer and curved; stipes apophysis strongly sclerotized and slightly S-bent; terminal apophysis partially forming hood over embolus. Legs (Fig. 4A, B): leg formula I>II>IV (>III) (but leg three missing); yellow, legs I and II with dorsal longitudinal dark band; lengths of segments (femur + patella + tibia + metatarsus + tarsus): pedipalp 0.19 + 0.12 + 0.06 + - + 0.34 = 0.71, I 1.52 + 0.56 + 1.46 + 1.86 + 0.62 = 6.01, II 1.46 + 0.43 + 1.21 + 0.90 + 0.59 = 4.50, III both legs missing, IV 1.18 + 0.28 + 0.96 + 1.02 + 0.40 = 3.84. Abdomen (Fig. 4A, B): 1.46 long, 0.93 wide; olive-green darker folium pattern which incorporates two intermittent white longitudinal lines; venter irregular olive-green, somewhat lighter centrally; spinnerets yellow-brown with olive-green (Fig. 4B).

Female (from Barrow Island; WAM T153635). Somatic characters of the female agree in general details with the male, except the dark lines on the legs are more irregular (see Fig. 5A, B). Total length 3.10. Carapace: 1.18 long, 0.78 wide. Eyes: AME 0.13, ALE 0.05, PME 0.09, PLE 0.05; row of eyes: AME 0.32, PME 0.25, PLE 0.54. Sternum: 0.50 long, 0.47 wide. Legs: leg formula I>II>IV>III; lengths of segments (femur + patella + tibia + metatarsus + tarsus): pedipalpu0.37 + 0.12 + 0.19 + - + 0.37 = 1.05, I 1.36 + 0.56 + 1.49 + 1.55 + 0.59 = 5.55, II 1.15 + 0.40 + 1.09 + 0.90 + 0.43 = 3.97, III 0.74 + 0.28 + 0.43 + 0.47 + 0.28 = 2.20, IV 1.12 + 0.40 + 0.99 + 1.05 + 0.43 = 4.00. Abdomen: 2.26 long, 1.40 wide.

Genitalia (Figs 5C–E, 6C, D): epigynum ovoid, wider than long and poorly sclerotised with narrow rim; no scape or scape rudiments evident; spermathecae ovoid, touching medially.

Variation. Total length males 2.50–2.65 (n = 3), females 3.05–3.20 (n = 4). Similar to L. sexta n. sp. there is no marked colour variation in the specimens of L. tumulus n. sp. examined by us, although in males the dark spots on the abdomen are sometimes less pronounced. A scape was not present in any of the females examined by us and no clear breakage point was evident.

Distribution. Currently only known from Barrow Island (Fig. 7).

Habitat preferences and life history. The habitat of L. tumulus n. sp. on Barrow Island is dominated by low spinifex (Triodia spp.) grassland and it occurs there mainly along the coast. Mature spiders have so far been found from September to December and from March to April, but numbers are too low for a reliable assessment of its phenology.