Marayniocus, Acosta, 2006

Acosta, Luis E., 2006, Marayniocus martensi, a new genus and a new species of Peruvian harvestmen (Arachnida: Opiliones: Gonyleptidae), Zootaxa 1325, pp. 199-210 : 201-202

Marayniocus gen. n.

Acrographinotus: Roewer 1959: 74 (in part).

Type species: Marayniocus martensi sp. n., here designated. Genus currently

monotypic.

Etymology: The generic name is derived from the Peruvian locality where the genus was collected (Hacienda Maraynioc, Departamento Junín); grammatical gender masculine.

Distribution: Central Peru, eastern Andean slopes, near the Chanchamayo valley, in high altitude grasslands of “eastern Puna”.

Diagnosis: Medium­sized Gonyleptidae (Pachylinae) , of robust habitus. Ocular mound with unpaired armature (median acute apophysis). Scutum unarmed and smooth, except for a pair of aligned paramedian granules in areas I–IV; area V and lateral areas with a row of granules. Free tergites I–II unarmed, with granulation similar to that of area V; free tergite III with a strong median apophysis (in ♂ larger than in ♀) and a row of smaller apophyses on each side. Dorsal anal plate unarmed, with a few granules. Pedipalpal femur unarmed (i.e. without prolateral subapical spine); tibia slightly dilated. Leg IV of ♂♂ with large apophyses on coxa, trochanter, femur, patella and tibia, the latter with a strong retroventral apophysis; leg IV in the ♀ with a spiny appearance due to numerous small, acute apophyses on femur, patella and tibia. Tarsal formula 6:8–9:7:7. Penis: subproximal portion of glans dilated; VPS fan­shaped, with dorsal concavity and an acute ventral projection .

Comparisons: Marayniocus gen. n. shares with Acrographinotus Holmgren, 1916 the "Roewerian" features: Tarsal formula 6:n:7:7, unpaired armature of ocular mound, scutum “unarmed” (at least, in the Roewerian sense!), and armature of free tergite III. This combination of character states is quite frequent among Andean pachylines of Peru: An identical characterization corresponds to the genus Junicus Goodnight & Goodnight, 1947 , and, except for the tarsal formula, also to Punagraphinotus Soares & Bauab, 1972 (5:n:6:6 tarsomers). The habitus of Acrographinotus intuitively allows a separation, considering the less developed coxal apophyses of the latter, and especially its more diagonal (and sideways) articulation of the ♂ trochanter IV ( Acosta 2001). In addition, no Acrographinotus species has a strong retroventral apophysis on tibia IV. In turn, the only named species of Junicus bears a distinct apophysis in an equivalent position on tibia IV ( Goodnight & Goodnight 1947; Mello­Leitão 1949; Roewer 1957; Soares & Bauab 1972), what undoubtedly led Roewer (1959) to confuse this material with Acrographinotus luteipalpis . The new genus shows some exomorphological similarities with the central Peruvian genera Palcapachylus Roewer, 1952 and Tarmapachylus Roewer, 1956 , both with species in the neighboring Tarma valley, upper Chanchamayo basin. These genera were described as bearing small tubercles in scutal areas III–IV ( Roewer 1952, 1956), which recall the paramedian granules of Marayniocus gen. n. The tarsal formula is also identical and the femoral armature of ♂♂ of the two known Palcapachylus species depicts a pattern similar to that of the new genus. However, both Palcapachylus and Tarmapachylus lack any kind of armature on free tergite III.

As stressed previously ( Acosta 2001, 2002), the most reliable features defining genera of Andean pachylines refer to the male genitalia, in particular the differently shaped VPS. In that character Marayniocus gen. n. shows the sharpest distinction, its flabelliform process being so far unique. In Acrographinotus the VPS consists of a slightly dilated portion, covered with an apical laminar expansion, and bearing a long ventral projection (the whole described as having the shape of a “combed ibis head”, see Acosta 2001). The VPS of Punagraphinotus resembles that of Acrographinotus , bearing a kind of ventral projection but without a "comb" ( Soares & Soares 1979). Junicus has a VPS strongly dilated, almond­shaped and dorsally oriented (also illustrated in Acosta 2001). The genital morphology of most remaining Andean pachylines has not been published yet, but all were examined by me. Penes of Palcapachylus , Tarmapachylus and Biconisoma Roewer, 1936 , all closely related to each other, are roughly similar to that of Junicus and thereby clearly different to Marayniocus gen. n. In contrast, Pichitus Roewer, 1959 , with a quite distinct external morphology, especially regarding the armature of femur IV in the ♂, as well as the curious and complex armature of the dorsal anal plate (see Roewer 1959), shows a surprising genital similarity with the “ Acrographinotus pattern”: The VPS of Pichitus bears an acute downward­pointing projection, but instead of having a membranous comb, the tip has lateral umbrella­shaped expansions. At the present state of knowledge it is very difficult to assess the actual affinities of Marayniocus gen. n., but the acute ventral projection of the flabelliform process might prove to be homologous to equivalent structures in Acrographinotus , Punagraphinotus and Pichitus . Other Andean pachyline genera (e.g. Polyacanthoprocta Mello­Leitão, 1927 and Punrunata Roewer, 1952 ) appear to be much more distant (Acosta, unpubl. data).