The family Galumnidae Jacot, 1925 includes 33 genera, 11 subgenera, 522 species and 33 subspecies (Subías 2004 updated in 2016). Among the genera, Galumna Heyden, 1826 is the largest: it includes seven subgenera and 192 species (including nine subspecies). Of these, the nominotypical subgenus Galumna contains the majority (172 species and nine subspecies). Aoki (1988) proposed Cosmogalumna as a new genus based on the presence of notogastral polygonal sculpture. Currently, Galumna (Cosmogalumna) contains 11 species, which are distributed in Oriental, Neotropic and Palearctic Regions (Subías 2004 updated in 2016, Ermilov and Friedrich 2016). Modified subgeneric diagnosis and an identificaiton key to known species were proposed by Ermilov and Corpuz-Raros (2015). However, based on our observation on notogastral microsetae by SEM and modified subgeneric diagnosis provided by Ermilov and Corpuz-Raros (2015), the subgeneric diagnosis of Galumna (Cosmogalumna) can be further modified as follows: with characters of the genus Galumna (Ermilov et al. 2013); lamellar setae inserted usually between lamellar and sublamellar lines, rarely between lamellar lines; notogaster with 10 pairs of microsetae or setal alveoli; surface of notogaster covered by reticulate pattern.

During taxonomic survey of oribatid mites from Japan, we found two Cosmogalumna species; first one is the type species of the subgenus, Cosmogalumna ornata Aoki, 1988, and the other species is new. The main goal of this paper is to describe the new species and provide an additional description of Cosmogalumna ornata.

12 specimens (two males, six females and four unknown specimens) collected from flourishing mosses growth on rocks near by the stream in Cryptomeria forest, Misatocho, Tsu city, Mie Prefecture, 34°45'49.8''N, 136°21'11.1''E, 419.4 m a.s.l., 20 November 2014, by W. Hagino. More than thirty specimens collected from soil and litter of evergreen forest, Nakanoshima Island, Toshima Village, Kagoshima Prefecture, 29°50'03.5''N , 129°54'01.6''E, 67 m a.s.l., 30 September 2015, by S. Shimano. More than 50 specimens collected from soil and litter of evergreen forest, Takarajima Island, Toshima Village, Kagoshima Prefecture, 29°9'13.5''N, 129°11'53.7''E, 25 m a.s.l., 28 September 2015, by W. Hagino. Two specimens collected from soil and litter of evergreen forest, Mt. Nishime, Okinawajima Island, Okinawa prefecture, 26°48'14.1''N, 128°15'37.5''E, 302 m a.s.l. 19 April 2006, by S. Shimano.

Oribatid mites were mounted in lactic acid on temporary cavity slides for measurement and illustration, with gam chloral liquied for permanent slides. For scanning electron microscopy (SEM), mites were fixed in 99.5% ethanol. Dehydration was conducted with graded ethanol series aceton and pentane. The specimens were placed on aluminum stubs with a double-stick carbon tape and coated with palladium-gold, then studied using Hitachi S3400-N scanning electron microscope. The morphological terminology used below is mostly that developed over many years by Grandjean (see Travé and Vachon, 1975 for references). All measurements are given as a range, with the mean in parentheses. Body length was measured in dorsal or ventral view, from the tip of the rostrum to the posterior edge of the ventral plate. Setal formulas are given as numbers per segment for appendages (from trochanter to tarsus, famuls included) as number per podosomal segment (I–IV).

Type species: Galumna (Cosmogalumna) ornata Aoki, 1988

ZOOBANK: 4DEC9599-7341-45E4-BD48-C1A4F56485E4

Diagnosis — Body length and width: 339 – 356 × 252 – 299 μm. Sexual dimorphism not observed. Sensillus with long stalk and short, rounded distally head with minute spicules. Lamellar setae inserted slightly anteriorly from line L. Dorsosejugal suture well developed. Middle part of notogaster and ventral plate ornamented with polygonal sculpture, remaining part minutely foveolated throughout. Notogastral porose areas with densely spotted surface. Medial pore (mp) on notogaster present. Surface of pteromorph ornamented with conspicuous granules centrally. Genital plates with conspicuous linear sculpture centrally.

Description — Measurements – Body length and width: 339 (344) 356 × 252 (272) 299 μm (n = 9).

Integument (Figs. 1, 2A-B, D, F, 3A–C, E, 4) — Body color brown to dark brown. Body surface minutely punctate. Prodorsum with faint longitudinal striations along its lateral margins. Surface of pteromorph ornamented with conspicuous granules centrally. Middle parts of notogaster and ventral plate ornamented with polygonal network (Figs. 1A-B, 4C-D). All porose areas surface densely spotted. Surface of mentum plate smooth. Genital plate centrally ornamented with conspicuous linear structure as in Figs. 2F and 3E.

Prodorsum (Figs. 1A, 2A, C, 3A, D, 4A) — Rostrum broadly rounded. Lamellar (L) and sublamellar (S) lines distinct, parallell, curving backwards. Rostral setae (ro) (approx. 29 μm) thin, slightly barbed. Lamellar setae (le) (approx. 18 μm) thin, slightly barbed, inserted just anterior to line L. Interlamellar setae (in) minute (approx. 3 μm), thin, smooth, hard to see. Sensillus (ss) with long stalk and short, rounded distally head, covered by minute spicules. Exobothridial setae not observed. Dorsosejugal porose areas (Ad) oval; posterior to seta in. Dorsophragmata (hy) near anterior notogastral margin.

Notogaster (Figs. 1A, 2B, D, 3A, C, 4B-C) — Dorsosejugal suture well developed. Ten pairs of minute (approx. 3 μm) notogastral setae present as Fig. 4B, hard to observe under the optical microscopy. Four pairs of circular porose areas present: Aa (diameter 14–16 μm) larger than others, A2 (diameter 8 – 10 μm) smaller than others, A1 and A3 (diameter 11–12 μm) almost same in size. Four pairs of lyrifissures (ia, im, ih, and ip) present; im anterior to setae lp, surrounded by polygonal network structure. A pair of opisthonotal gland openings (gla) anterior to A2.

Gnathosoma (Fig. 2E) — Morphology of subcapitulum, palp and chelicera typical for subgenus (see Ermilov and Corpuz-Raros 2015). Setation of palp and chelicera typical for subgenus.

Ventral side (Figs. 1B, 2F-G, 3B, E-F, 4D) — Six pairs of thin, short, smooth genital setae (approx. 5 μm); g ₁, g ₂, and g ₃ inserted on anterior margin of genital plate; g ₄, g ₅, and g ₆ arranged longitudinally. One pair of minute aggenital setae (approx. 3 μm) posterior of genital plates. Two pairs of thin, smooth anal setae (approx. 5 μm) arranged longitudinally. Three pairs of minute adanal setae (approx. 3 μm); ad ₁ and ad ₂ posterior to anal plates, ad ₃ situated on lateral side of anal aperture. Adanal lyrifissures iad along edge of anal plate, lateral to ad ₃. Setal formula of epimera 2–0–1–1. Posterior porose area (Ap) large (8 μm wide), oval, posterior to anal plate.

Legs (Fig. 5, Table. 1) — All legs tridactylous. Morphology of leg segments, setae and solenidia generally typical for species of the subgenus Galumna (Cosmogalumna) and other Galumnidae (Engelbrecht 1972; Ermilov and Anichkin 2013). Leg setation (Tr–Fe–Ge–Ti–Ta) including famulus: leg I, (1–4–3–4–20); II, (1–4–3–4–15); III, (1–2–1–3–15); IV, (1–2–2–3–12). Solenidiotaxy (Ge–Ti–Ta): I, (1–2–2); II, (1–1–2); III, (1–1–0); IV, (0–1–0).

Material examined — 12 specimens (two males, six females and four unknown specimens) collected from flourished mosses growing rocks near by the stream in a cryptomeria forest, Misatocho, Tsu city, Mie Prefecture, 34°45'49.8''N, 136°21'11.1''E, 420 m a.s.l., 20 November 2014, by W. Hagino.

Type deposition — Holotype (NSMT–Ac 14208, female) on slide: mosses growth on the rocks by the stream in a Cryptomeria forest, Misatocho, Tsu city, Mie Prefecture, 34°45'49.8''N, 136°21'11.1''E, a.s.l., 419.4 m, 20 November 2014, by W. Hagino. Two paratypes (NSMT–Ac 14209, and 14210, one male and one female) on slide: same data as holotype. The holotype and paratypes are to be deposited in the National Museum of Nature and Science, Tsukuba, Japan Additional non-type specimens from the same locality as holotype, are preserved in the collections of W. Hagino.

Distribution — At present, this species only known from Mie Prefecture, Japan.

Etymology — The species epithet refers to the polygonal sculpturing of the middle part of notogaster and ventral plate.

Remarks — Among the 11 species of Galumna (Cosmogalumna), Galumna (Cosmogalumna) centroclathrata n. sp. most closely resembles G. (C.) praeoccupata Subías, 2004 (=Cosmogalumna imperfecta Aoki and Hu, 1993) from Yunnan Province, China in 1) long sensillus having rounded distally head with minute spicules, 2) polygonal sculpture on the middle part of notogaster and middle part of ventral plate, and 3) presence of medial pore on the notogaster. However, Galumna (Cosmogalumna) centroclathrata n. sp. differs from G. (C.) praeoccupata in having 1) conspicuous granular ornamentation on the whole surface of pteromorph, 2) polygonal sculpture on the dorsal side of notogaster has a form of a pair of weak arches connected in the middle part of notogaster (bended at both lyrifissure im and at the middle point of setae lp) spreaded transversely up to the mid-distance between notogastral setae la and gla at both side of notogaster, while in G. (C.) praeoccupata Subías, 2004, it has a form of straight band terminating on each side with a large cloud-like expansion, spreaded longitudinally between notogastral setae lm and nearby gla, spreaded transversely beyond the mid-distance between notogastral setae la and gla. 3) conspicuous linear sculpture on the genital plates.

Supplementary description — Measurements – Body length and width: 320 (336) 348 × 259 (266) 285 μm (n = 10).

Integument (Figs. 6, 7A–C, E–H, 8A–F) — Body color brown to dark brown. Body surface fully foveolated minutely. Prodorsum with dense granules and striations; especially central part with larger granules, faint longitudinal striations along its lateral margins. Surface of pteromorph fully ornamented with conspicuous granules, with fine granules in anterior part. Notogaster fully ornamented with polygonal network. Surface of all porose areas ornamented with multiple conspicuous granules (approx. 3 μm) (see Aoki (1988), fig. 3). Anterior margin of ventral plate granulated, posterior to genital aperture ornamented with polygonal network except smooth posterior edge. Mentum plate with irregular granules. Each genital plate ornamented with granules, fine wrinkles in its distal edge, and longitudinal striation running nearly parallel with the median border. Surface of anal plate ornamented with irregularly shaped granules.

Prodorsum (Figs. 6A, 7A, D, 8A) — Rostrum broadly rounded. Lamellar and sublamellar lines distinct, parallell, curving backwards. Rostral setae (approx. 26 μm) thin, slightly barbed, hard to observe from dorsal side. Lamellar setae (approx. 15 μm) thin, slightyly barbed, inserted just anterior to line L. Interlamellar setae minute (approx. 2 μm) thin, smooth, hard to discern. Sensillus with long stalk and short, rounded distally head, covered by minute spicules. Exobothridial setae not observed. Dorsosejugal porose areas oval; posterior to seta in. Dorsophragmata near anterior notogastral margin.

Notogaster (Figs. 6A, 7B-C, 8A, C-D) — Dorsosejugal suture well developed. Ten pairs of minute (approx. 3 μm) notogastral setae present as Fig. 8D, hard to observe under optical microscope. Four pairs of circular porose areas present: Aa (diameter 12 – 13 μm) larger than others, A2 (diameter 5 – 6 μm) smaller than others, A1 and A3 (diameter 10 – 11 μm) almost same in size. Four pairs of lyrifissures (ia, im, ih, and ip) present. Opisthonotal gland openings anterior to A2.

Gnathosoma (Figs. 7E-F) — Morphology of subcapitulum, palp and chelicera typical for genus (see Ermilov and Corpuz-Raros 2015). Setation of palp and chelicera typical for subgenus (see Ermilov et al. 2011).

Ventral side (Fig. 6B, 7G-H, 8B, E-8F) — Six pairs of thin, short, smooth genital setae (approx. 5 μm); g ₁, g ₂, and g ₃ inserted on anterior margin of genital plate; g ₄, g ₅, and g ₆ arranged longitudinally. Pair of minute aggenital setae (approx. 3 μm) in posterior region of genital plates. Two pairs of thin, smooth anal setae (approx. 4 μm) arranged longitudinally on anal plates. Three pairs of minute adanal setae (approx. 3 μm); ad ₁ and ad ₂ posterior to anal plates, ad ₃ situated on lateral side of anal aperture. Adanal lyrifissures iad along edge of anal plate, lateral to ad ₃. Setal formula of epimera 2–0–1–1. Posterior porose area oval (5 μm wide), posterior to anal plate.

Legs (Table 1) — All legs tridactylous. Morphology of leg segments, setae and solenidia generally typical for species of the subgenus Galumna (Cosmogalumna) and other Galumnidae (e.g. Engelbrecht 1972; Ermilov and Anichkin 2013). Leg setation (Tr–Fe–Ge–Ti–Ta) including famulus: leg I, (1–4–3–4–20); II, (1–4–3–4–15); III, (1–2–1–3–15); IV, (1–2–2–3–12). Solenidiotaxy (Ge–Ti–Ta): I, (1–2–2); II, (1–1–2); III, (1–1–0); IV, (0–1–0).

Material examined — Five males and five females collected from soil and litter of evergreen forest, Nakanoshima Island, Toshima Village, Kagoshima Prefecture, 29°50'03.5''N, 129°54'01.6''E, 67 m a.s.l., 30 September 2015, by S. Shimano. More than 50 specimens collected from soil and litter of evergreen forest, Takarajima Island, Toshima Village, Kagoshima Prefecture, 29°9'13.5''N, 129°11'53.7''E, 25 m a.s.l., 28 September 2015, by W. Hagino. Two specimens collected from soil and litter of evergreen forest, Mt. Nishime, Okinawajima Island, Okinawa Prefecture, 26°48'14.1''N, 128°15'37.5''E, 302 m a.s.l., 19 April 2006, by S. Shimano.

Distribution — At present, this species is known from Nakanoshima Island, Takarajima Island, Tokashiki Island, Miyako Island, Ishigaki Island, Yonaguni Island, and Okinawa Island in Southwestern Japan (Aoki, 2009).

Two of Cosmogalumna species seem to be endemic to one of the southwestern islands of Japan: G. (C.) hiroyoshii from Ishigakijima Island and G. (C.) yonaguniensis from Yonagunijima Island. In contrast, G. (C.) ornata is recorded commonly, from various localities in southwestern archiperago in Japan, e.g. Nakanoshima Island as type locality, Takarajima Island, Tokashikijima Island, Miyakojima Island, Ishigakijima Island, Yonagunijima Island, and Okinawajima Island (Aoki, 2009). Therefore, this new species of Galumna (Cosmogalumna) found in Mie prefecture is the first record of the subgenus from Honshu Island in Japan, and the northernmost record of this subgenus in the world.

Ermilov and Corpuz-Raros (2015) mentioned “notogaster with 10 pairs of setal alveoli” in their modified subgeneric diagnosis based on Aoki (1988). However, our SEM observation on the specimens of G. (C.) ornata Aoki, 1988 from its type localitiy showed the presence of ten pairs of very short (approx. 3 μm) notogastral setae (Fig. 8D).

Aoki (1988) described lamellar setae as inserted between carinae L and S, however, our observation exhibits that the lamellar setae were inserted slightly anterior to the L lines. Aoki (1988) overlooked the location of setae. Ermilov and Corpuz-Raros (2015) mentioned “lamellar setae inserted usually between lamellar and sublamellar lines, rarely between lamellar lines” and our observation supports their modified subgeneric diagnosis. These corrections should be considered in any future identification of the species.

We thank Dr. Satoshi Kagiwada (Faculty of Life Science, Hosei University) for supporting SEM observation, Dr. Atsushi Takashima (The Yona Field, Faculty of Agriculture, University of the Ryukyus) and Dr Takeshi Sasaki (The University Museum Fujukan, University of The Ryukyus) for enormous help to sampling in Mt. Nishime, Dr. Shimpei Hiruta (Department of Science, Hokkaido University) for heartfelt help during sampling tour in Tokara Islands. And we also thank to Dr. Hiroshi Kajihara (Department of Science, Hokkaido University), and Dr. Jun-ichi Aoki (Professor Emeritus, Yokohama National University), for their valuable comments were constructive help to us.

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