Acanthopachylus Roewer, 1913

Acosta, Luis E., 2021, The return of a forgotten harvestman: revalidation of Gonyleptes robustus Holmberg, 1876, as the second species of Acanthopachylus Roewer, 1913 (Arachnida, Opiliones, Gonyleptidae), Zootaxa 5040 (3), pp. 428-438 : 428-438

Acanthopachylus Roewer, 1913

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Gonyleptes: Kirby 1819: 450 (in part); Holmberg 1876: 28 (in part).

Pachylus: Holmberg 1878: 70 (in part); Sørensen 1884: 639 (in part).

Acanthpachylus Roewer 1913: 50 (in part). Incorrect original spelling (see below).

Acanthopachylus: Roewer 1923: 411 (in part); Ringuelet 1959: 274 [synonymy]; Kury 2003: 153 [synonymy].

Type species. Gonyleptes aculeatus Kirby, 1819 , by original designation.

Included species. Acanthopachylus aculeatus ( Kirby, 1819) and A. robustus ( Holmberg, 1876) comb. nov. ( Figs. 1–2 ).

Excluded combinations. Acanthopachylus butleri ( Thorell, 1877) : Roewer 1913 (nowadays assigned to genus Pachyloidellus Müller, 1918 : Acosta 1993); Acanthopachylus crassus ( Roewer, 1943) : Capocasale & Bruno Trezza 1964 (currently in Pachylus Koch, 1839a : Acosta 1993, 2021).

Note on the genus spelling. In the original publication, Roewer (1913) consistently spelled the genus name as Acanthpachylus [ NZ, 1: 22]; 10 years later he emended it by inserting a missing “o”, to get the current spelling Acanthopachylus . Although Roewer (1923) does not explain the reasons for the change, according to ICZN Art. 33.2.1. this action is clearly intentional (i.e., the original and the modified spellings are both cited by Roewer 1923), what constitutes primarily an unjustified emendation [cf. NZ, 1: 17]. Moreover, the original spelling Acanthpachylus cannot be interpreted as an inadvertent error, since this category is not met by the incorrect use of connecting vowels in forming a name (ICZN, Art. 32.5.1.). In any case, the emended spelling Acanthopachylus gained prevailing usage (cf. synonymy in Kury 2003), so it became by force of use a “justified emendation” (ICZN Art. 33.2.3.1.), i.e., with no separate authorship and date, rendering Acanthpachylus as the “incorrect original spelling”.

Distribution. Acanthopachylus aculeatus auct. has been deemed to be one of the most widespread harvestmen in South America. It was cited from Cayenne in the French Guiana (presumed “ types ” of Gonyleptes acanthurus , according to Roewer 1923: 413) up to the Strait of Magellan, in the southernmost tip of the continent ( Roewer 1929: 190, one female). Mello-Leitão (1939) argued that the species spreads over “toute l’Amérique du Sud, du coté atlantique”, an exaggerated assertion repeated by B. Soares & H. Soares (1954). Eisner et al. (2004), citing Capocasale & Bruno Trezza (1964), still claimed that the species extends from the Guianas to Argentina. The only well documented records of Acanthopachylus , however, come from southern Brazil (Rio Grande do Sul State), Uruguay and Argentina ( Ringuelet 1959; Capocasale 1968; H. Soares & B. Soares 1986; Kury 2003). Despite this restriction, the genus distributes over an extensive range on grassland-type biomes (Pampas in Argentina, similar savanna environments in Uruguay and Brazil; Acosta 2002), along with some peripheral records in neighboring ecoregions ( Fig. 3 ). Both species have marked synantropic habits.

Figures

FIGURE 1. Live males of Acanthopachylus aculeatus (A–B: El Caracol, Departamento Rocha, Uruguay; photos by Javier A. Canteros), and Acanthopachylus robustus comb. nov. (C–D: Lago Lugano, Buenos Aires, Argentina; photos by Ricardo A. Palonsky—RAP).All photos used with permission of the authors.

FIGURE 2. Diagnostic characters to distinguish male Acanthopachylus aculeatus (A–B) (MHNM, Departamento Lavalleja, Uruguay) and Acanthopachylus robustus comb. nov. (C–D) (LEA 000.428, Sierra de la Ventana, Buenos Aires Province, Argentina). A, C: dorsal scutum, coxae, trochanter and femur IV, dorsal view; B, D: coxa (with rear end of body), trochanter, femur and patella IV, prolateral view. Scale bars: 1 mm.

FIGURE 3. Geographical distribution of Acanthopachylus aculeatus (Kirby) (blue dots) and A. robustus (Holmberg) comb. nov. (red dots) in Argentina, Uruguay and southern Brazil. Records with verified taxonomic identity are denoted with full color symbols, small white dots represent literature citations not checked as yet. Ecoregions according to Olson et al. (2001); both grassland-type ecoregions (Humid Pampas on the Argentinean side, Uruguayan Savanna in Uruguay and southern Brazil) are given the same color (light yellow). APAF: Alto Parana Atlantic Forests; HCH: Humid Chaco; MS: Southern Cone Mesopotamian Savanna; ESP: Espinal. Inset (bottom right): location of the area represented in South America.