Metonomastus petrovi, Antic, Dragan, Vagalinski, Boyan, Stoev, Pavel & Golovatch, Sergei, 2018

Antic, Dragan, Vagalinski, Boyan, Stoev, Pavel & Golovatch, Sergei, 2018, Two new species of the millipede genus Metonomastus Attems, 1937 from the Balkan Peninsula (Diplopoda, Polydesmida, Paradoxosomatidae), ZooKeys 786, pp. 43-57 : 43

Metonomastus petrovi sp. n. Figs 1, 2, 3, 4

Material examined.

Holotype male (NMNHS), Bulgaria, Western Rhodopi Mts., Satovcha District, Cave Stapalkata, 650 m a.s.l., clay-guano, 17.VI.2006, B. Petrov & P. Stoev leg.

Paratypes.

2 males, 5 females (NMNHS), same data as holotype.

Additional material.

2 females, 1 juvenile (NMNHS), Bulgaria, Western Rhodopi Mts., Pazardzhik District, Peshtera town, Cave Snezhanka, 19.IV.2009, P. Beron leg.; 1 male, 1 female (NMNHS), Bulgaria, Plovdiv, Bunardzhik Hill, under decaying wood, 10.IV.2018, P. Mitov leg.

Etymology.

The species is named after Boyan Petrov, a renowned Bulgarian mountaineer, a dear friend and colleague zoologist from the National Museum of Natural History, Sofia, who disappeared in Tibet in May 2018 during the ascent of his 11th eight-thousander, Shishapangma. Boyan was one of the collectors of this new species. Noun in genitive case.

Diagnosis.

The new species belongs to the Metonomastus group of species with three acropodital branches, but clearly differs from both previously described species in this group, M. strasseri Hoffman & Lohmander, 1968, and M. pomak Golovatch & Stoev, 2004, by the presence of a strongly developed, beak-shaped solenomere, by the completely reduced solenophore and by the development of a strongly arched, microspiculate, ventromesal, acropodital process.

Description.

Length 4.4-4.8 mm (males), 4.2-5.5 mm (females). Width of midbody rings 0.31-0.37 and 0.33-0.42 mm (males), 0.35-0.42 and 0.42-0.47 mm (females) on pro- and metazonae, respectively. Holotype male 4.8 mm long, 0.37 and 0.42 mm wide on midbody pro- and metazonae, respectively.

Body moniliform (Figure 1A), with 19 segments in both sexes. Colouration entirely pallid. Texture microreticulate throughout (Figure 2A, B).

Head densely pubescent throughout, clypeolabral region densely setose. In males, width of head (0.41-0.5 mm broad) >> collum ≤ ring 2 ≤ 3 ≥ 4 <5 ≥ 6 = 17; thereafter body gradually, but significantly tapering. In females, width of head (0.42-0.5 mm broad) >> collum = ring 2 <3 = 4 <5 = 17; thereafter body rather rapidly tapering; in larger females, ring 5 = 14 <15 = 17.

Antennae (Figure 2C, D) long, clavate, in situ reaching behind ring 2 when stretched dorsally. Antennomere length 2 = 3 = 6> 4 = 5 = 7> 1, 6th being the thickest, both 6th and 5th each with a compact group of bacilliform sensilla dorso-apically. Interantennal isthmus ca 0.7 times as broad as diameter of antennal socket.

Collum with 3 rows of setae; two rows of similar setae per postcollum metatergum: one frontally, the other caudally, setae long and simple. Metaterga (Figure 2A, B) with a weak, mid-dorsal, transverse sulcus on rings 5 to 17; sulcus absent from 18th. Paraterga (Figure 2A, B) laterally extremely poorly developed, being very faintly delimited by a shallow sulcus only dorsally. Certain midbody rings occasionally with visibly more or less strongly developed paranota compared to neighboring rings. Ozopores indistinct, located near posterior margin of paraterga; pore formula normal. Strictures between pro- and metazonae very faintly striolate, deep and narrow. Pleurosternal carinae present on ring 2 as small lobes, thereafter missing. Limbus faintly microcrenulate. Epiproct long, slender, nearly half as long as telson height. Hypoproct semi-circular, 1+1 strongly separated caudal setae borne on minute knobs. Sterna broad and weakly impressed.

Legs (Figure 2B) about 1.1-1.2 times as long as midbody height in males, 0.8-0.9 times in females, without modifications, only pregonopodal male prefemora slightly bulged dorsally (Figure 3A, B).

Gonopods (Figs 3C, 4): Coxite (cx) massive, moderately long, dorsolaterally very sparsely setose. Prefemorite (pf) somewhat longer than acropodite, densely setose ventrally. Postfemoral sulcus distinct, short, traceable on median and, partly, ventral sides. Acropodite consisting of three branches: mesal process (ss) curved and saddle-shaped, ventromesal process (vm) more strongly arched, its outer surface microspiculate (Figure 4F), solenomere (sl) robust, blunt, somewhat beak-shaped, ventrolaterally with a deep and broad transverse groove. Seminal groove running on mesal side all along prefemorite, then shifting dorsally on acropodite, terminating ventromesally on solenomere.

Remarks.

This species is known both from caves and from an epigean environment. Like some other representatives of the genus, this new species can be considered a troglophile.