Sinostoma, Martens, Jochen, 2016

Martens, Jochen, 2016, Sinostoma yunnanicum, the first nemastomatine harvestman in China (Arachnida: Opiliones: Nemastomatidae), Zootaxa 4126 (3), pp. 444-450 : 445

Sinostoma n. gen.

Type species: Sinostoma yunnanicum n. sp. (by original designation).

A genus of Nemastomatidae within the subfamily Nemastomatinae as here defined and comprising one species. Gender of name is neuter.

Genital morphology: Penis characterized by rather unspecialized truncus, moderately slender, slightly inflated distally; the muscle-bearing basal bulb large, markedly inflated but rather compact, truncus a straight continuation of bulb, the latter not incised medially. Glans small, inconspicuous, short, not well separated from truncus; armament of glans simple with a few stiff spines in a dorsally and ventrally symmetrical arrangement, stylus short and straight.

Cheliceral apophysis of basal article well-marked but low with a distal-directed hook, secretion area a bowllike excavation on the medial side of the apophysis.

Body armed with rows of anvil-like tubercles on the dorsal side.

Distribution. Only one species known from a single locality in northern Yunnan, SW China and described below.

Name. Sin- refers to China, stoma Greek mouth; this combination alludes to Nemastoma , the name-giving genus of Nemastomatidae ; nema Greek thread, refers to the longish unarmed pedipalps of most species of this family which originate close to the mouth.

Relations. Rows of anvil-like tubercles forming lines and encircling the dorsal scutum magnum and all or parts of the dorsal scutal areas, probably corresponding to “segments”, are present in several nemastomatine genera and have been documented in Mitostoma Roewer, 1951 , Carinostoma Kratochvíl, 1958 ( Martens 1978) and Acromitostoma Roewer, 1951 ( Rambla 1983) and are excessively developed in all New World ortholasmatines. Apparently, these dorsal ornaments represent independent developments, at least when following the (still incomplete) molecular-genetic results of Schönhofer & Martens (2012). Two of the relevant genera analyzed are placed at different branches of the molecular-genetic tree and are not closely related.

Alternatively, this dorsal armament may have been lost at various stages of nemastomatine evolution. This view is backed by the fact that nearly all ortholasmatine genera and species exhibit rich and even more elaborate scutal ornamentation, which is much reduced or even lacking in the few Asian species except for Cladolasma damingshan Zhang & Zhang, 2013 ( Shear & Gruber 1983, Shear 2010, Zhang & Zhang 2013). Thus, rows of anvil-shaped tubercles may represent a plesiomorphic character of nemastomatid morphology. In addition, equally shaped thorns turn up as coxal-rim denticles in most species. Consequently, this character is not useful to infer phylogenetic relationships.