A survey of the Sumatran Ctenidae (Araneae). 4. A new species of Acantheis Thorell, 1891 with unique copulatory organs morphology Author Fomichev, Alexander A. Altai State University, Lenina Pr., 61, Barnaul, RF- 656049, Russia. Author Omelko, Mikhail M. 0000-0002-1556-6248 Federal Scientific Center of East Asia Terrestrial Biodiversity, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russia. & Far Eastern Federal University, Laboratory of ecology and evolutionary biology of aquatic organisms (LEEBAO), Institute of World Ocean, Vladivostok 690091, Russia. omelkom@gmail.com Author Marusik, Yuri M. 0000-0002-4499-5148 Institute for Biological Problems of the North FEB RAS, Portovaya Str. 18, Magadan 685000, Russia. & Department of Zoology & Entomology, University of the Free State, Bloemfontein 9300, South Africa. yurmar@mail.ru text Zootaxa 2024 2024-11-05 5536 3 492 500 http://dx.doi.org/10.11646/zootaxa.5536.3.9 journal article 10.11646/zootaxa.5536.3.9 1175-5326 14239144 F8E9CC7A-AB68-4F72-AA61-820C357DC601 Acantheis kazantsevae sp. nov. Figs 1–32 Types. INDONESIA : Sumatra Island : Aceh Prov. : holotype ♂ ( ISEA , 001.9097) , Ketambe Vil. [ 03°41′N , 97°39′E ], 400–500 m , under stones in pristine forest, 1988 (precise date unknown), unknown collector. Paratype : 1♀ ( ISEA , 001.9098), with same data as for holotype . Etymology. The specific name is a matronym in honor of Yulia G. Kazantseva ( Novosibirsk , Russia ), talented psychiatrist and friend of the senior author. Diagnosis. The new species differs from all other species of Acantheis by having a twisted tegular apophysis with two arms: a large boomerang-shaped anterior one ( AT ) and a posterior one ( PT ) ( vs . tegular apophysis not twisted), embolus with long pointed arm ( AE ) ( Figs 16–17 , 20–21 ) ( vs . AE absent) and epigyne with short anchor-shaped septal base ( SB ) ( Figs 22 , 25 ) ( vs . high, square, trapezoidal or elliptical SB ). Description. Male ( Figs 1–2 , 5–7, 10 ). Total length 4.25. Carapace: 2.1 long, 1.8 wide. Opisthosoma: 2.1 long, 1.4 wide. Carapace yellow-gray with yellow median band. Clypeus brown-gray. Chelicerae, labium, endites, sternum, and coxae yellow. Palps and legs dirty-yellow. Abdomen yellow-gray, with yellow median band dorsally. Venter of opisthosoma yellow. Spinnerets yellow-gray. Cephalic part with a tuft of long, light setae between PME. Eye sizes and interdistances: AME 0.14, ALE 0.09, PME 0.23, PLE 0.23; AME–AME 0.07, AME–ALE 0.13, PME–PME 0.09, PME–PLE 0.1, AME–PME 0.09, ALE–PLE 0.11. Clypeus height at AME 0.20, at ALE 0.39. Chelicerae with 3 promarginal and 5 retromarginal teeth. Femur I/carapace length ratio 1.57. For palp and leg measurements see Table 1 . For palp and leg spination see Table 2 . TABLE 1. Palp and legs measurements of male of Acantheis kazantsevae sp. nov.

Fe	Pa	Ti	Mt	Tr	Total
Palp	1.23	0.58	0.78	–	1.08	3.67
Leg I	3.3	0.98	3.98	3.48	1.28	13.02
Leg II	2.88	0.85	3.05	2.85	1.13	10.76
Leg III	2.6	0.7	2.45	2.65	1.1	9.5
Leg IV	3.93	0.83	3.68	4.75	1.38	14.57

TABLE 2. Palp and legs spination of male of Acantheis kazantsevae sp. nov.

Fe	Pa	Ti	Mt
Palp	3d 1p 1r	1p	1d 2p	–
Leg I	3d 3p 1r	-	9 paired v	4 paired v
Leg II	2d 3p 4r	-	1p + 8 paired v	4 paired v
Leg III	4d 5p 4r	1p 1r	1d 2p 2r + 2 paired v	2d 3p 3r + 1single and 2 paired v
Leg IV	3d 4p 3r	-	1d 2p 2r + 3 paired v	4d 4p 3r + 1 single and 3 paired v

FIGURES 1–4 . Habitus of Acantheis kazantsevae sp. nov. , male (1–2) and female (3–4). 1, 3—dorsal; 2, 4—ventral. Scale: 2 mm. FIGURES 5–10 . Prosoma (5), cephalic part (6), chelicera (7), leg I (8), femur I (9) and spinnerets (10) of Acantheis kazantsevae sp. nov. 5—male, lateral; 6—ditto, anterior; 7—ditto, posterior; 8, 9—female, retrolateral; 10—male, ventral. Scale: 5=0.5 mm, 8=1 mm; 6–7, 10=0.2 mm. Abbreviation: v —ventral spines. Male palp as shown in Figs 11–21 . Femur 5.3 times longer than wide. Patella 2.0 times longer than wide. Tibia ca. 2.2 longer than wide, with 3 very long spines, longest ca. 0.9 of tibia length. Retrolateral tibial apophysis ( RTA ) shorter than tibia diameter, with rounded anterior part, with 2 small spines. Ventral tibial apophysis ( VTA ) larger than RTA . Cymbium spineless, ca. 2.4 times longer than wide. Cymbial tip about 0.42 of cymbial length, slightly shorter than bulb. Subtegulum ( St ) large, oval. Tegulum ca. 1.2 times longer than wide. Tegulum ( T ) with prolateral extension ( TE ). Spermophor ( Sf ) encircling the entire tegulum. Posterior arm of tegular apophysis ( PT ) ear-shaped, with a deep cavity ( TC ) at base of anterior arm ( AT ). AT large, boomerang-shaped.Apical part of AT retrolaterad and basal part with large, ventral extension ( VE ). Basal part of AT bulged and apical one with distinct ridges ventrally. Conductor ( C ) membranous, elliptical. Basal part of embolus ( E ) with ventrad bulge ( VB ) and proximad spur ( ES ). Embolic arm ( AE ) almost straight, longer than embolic tip ( ET ), protruding from retrolateral side of embolus. Embolic tip straight, about 0.7 of embolic arm length. FIGURES 11–19. Male palp (11–15) and bulb (16–19) of Acantheis kazantsevae sp. nov. 11, 16—prolateral; 12, 17—ventral; 13, 15, 18—retrolateral; 14—dorsal; 19—anterior. Scale: 0.2 mm. Abbreviations: AE —embolic arm, AT —anterior arm of tegular apophysis, C— conductor, E— embolus, ES —embolic spur, ET— embolic tip, PT —posterior arm of tegular apophysis, Sf— sperm duct, St— subtegulum, T— tegulum, TC —cavity of tegular apophysis, TE— prolateral extension, VB— ventrad bulge, VE —ventral extension, VTA —ventral tibial apophysis. FIGURES 20–24. SEM photographs of bulb (20), tegular apophysis (21), epigyne (22) and ventral spine’s locking mechanism in female’s femorae I (23–24) of Acantheis kazantsevae sp. nov. Scale: 20=0.3 mm; 21–22=0.1 mm; 23–24=0.02 mm. Abbreviations: AE— embolic arm, AT —anterior arm of tegular apophysis, C— conductor, CO— copulatory opening, ET— embolic tip, PT —posterior arm of tegular apophysis, St— subtegulum, TA— tegular apophysis, TC —cavity of tegular apophysis, TE— prolateral extension. Female ( Figs 3–4 , 8–9 ). Total length 5.35. Carapace: 2.45 long, 2.0 wide. Opisthosoma: 2.8 long, 1.95 wide. Carapace and clypeus as in male. Chelicerae, endites and labium yellow brown. Sternum and coxae as in male. Palps, legs, opisthosoma and spinnerets as in male. Cephalic part with a tuft of long light setae between PME. Eye sizes and interdistances:AME 0.16, ALE 0.11, PME 0.29, PLE 0.23; AME–AME 0.1, AME–ALE 0.17, PME–PME 0.11, PME–PLE 0.14, AME–PME 0.1, ALE–PLE 0.14. Clypeus height at AME 0.19, at ALE 0.39. Chelicerae with 3 promarginal and 5 retromarginal teeth. Femur I/carapace length ratio 1.27. Femur I with one row of flexible ventral spines equipped with locking mechanism ( Figs 23–24 ). For palp and legs measurements see Table 3 . For palp and legs spination see Table 4 . Epigyne and internal genitalia as shown in Figs 22 , 25–30 . Epigynal plate 1.6 times wider than long. Septal base ( SB ) anchor-shaped. Septal stem ( SS ) 1.5 times shorter than septal base width. Lateral teeth ( LT ) distinct, almost parallel in posterior view. Receptacles ( Re ) circular, subdivided into 2 chambers: flattened chamber I ( ReI ) and elliptical chamber II ( ReII ). Copulatory ducts ( CD ) very short, tightly pressed to ReI . Distribution. Known from the type locality only ( Figs 31–32 ).