Acanthopachylus robustus ( Holmberg, 1876 ) Acosta, 2021

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 robustus ( Holmberg, 1876) comb. nov., revalidated

( Figs. 1C–D , 2C–D )

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Gonyleptes robustus Holmberg 1876: 29 . Type: one male, “near Palermo, Collection of the author”, lost.

Pachylus robustus: Holmberg 1878: 71 .

Pachylus mesopotamogalis Weyenbergh 1878: 316 . Types: ♂ ♀ lost. Syn. nov. (formerly under A. aculeatus: Ringuelet 1959 ).

Pachylus aculeatus: Sørensen 1884: 641 (in part) [= Gonyleptes robustus , synonymy incorrect].

Acanthpachylus aculeatus: Roewer 1913 (in part): 51; figs. 19, 20 are A. robustus comb. nov.

Acanthopachylus aculeatus: Roewer 1923 (in part): 412, figs. 507, 508 (drawings are A. robustus comb. nov., but materials are mixed); B. Soares & H. Soares 1954: 233 (in part.); Ringuelet 1953 (in part): 161 [= Heteropachyloidellus serrulatus ]; 1955 (in part): 283–288 [= Heteropachyloidellus dimorphicus = H. paucigranulatus = H. marginatus = Pachyloidellus tricalcaratus = Pachyloidellus fuscus , the latter synonym of Pachyloidellus butleri: Acosta 1993 , = H. robustus , actually referable to A. aculeatus comb. nov.]; 1959 (in part): 275 [= Pachylus mesopotamogalis , actually refers to A. robustus comb. nov.] [all illustrations depict A. robustus comb. nov.]; H. Soares & B. Soares 1986: 87, figs. 1, 2 (in part) [= Guascaia ypsilonota ]; Acosta & Maury 1998: 580; Acosta 2002: 81 (new material of A. robustus comb. nov. cited as A. aculeatus ); Kury 2003: 154 (in part).

Pachyloidellus tricalcaratus Roewer 1923: 448 , fig. 564 [Types: SMF, ♀ Buenos Aires, examined]. Syn. nov. (formerly under A. aculeatus: Ringuelet 1955 ).

Heteropachyloidellus dimorphicus Mello-Leitão, 1927: 15 [Types: MNRJ, ♂ ♀ probably Rio Grande do Sul, examined]. Syn. nov. (formerly under A. aculeatus: Ringuelet 1955 ).

Heteropachyloidellus paucigranulatus Mello-Leitão, 1931: 88 [Types: MACN, MNRJ, ♂ ♀ Carmelo, Uruguay, examined]. Syn. nov. (formerly under A. aculeatus: Ringuelet 1955 ).

Heteropachyloidellus serrulatus Mello-Leitão, 1931: 88 , fig. 5 [Types: MACN, MNRJ, ♂ ♀ Entre Ríos, examined]. Syn. nov. (formerly under A. aculeatus: Ringuelet 1953 ).

Heteropachyloidellus marginatus Mello-Leitão, 1932: 150 [Type: MNRJ, ♀ Rio Grande do Sul, examined]. Syn. nov. (formerly under A. aculeatus: Ringuelet 1955 ).

Guascaia ypsilonata vel ypsilonota Mello-Leitão, 1935a: 1 , 3, fig. 1 [Types: MNRJ, ♂ ♀ Porto Alegre, Rio Grande do Sul, examined—two original spellings, ypsilonota selected by Mello-Leitão, 1935b: 101, acting as first reviser: ICZN Art. 24.2.4.]. Syn. nov. (formerly under A. aculeatus: H. Soares & B. Soares, 1986 ).

Identification. Holmberg’s (1876) description contains unequivocal hints of the identity of this species, very especially the strong S-curvature of femur IV ( Figs. 1D , 2D ), and the basal truncated apophysis in the same leg segment ( Fig. 2C ). The locality “near Palermo”, now embraced within the urban area of Buenos Aires city, is fully consistent with the known distribution of A. robustus comb. nov.

Type locality. Buenos Aires, near Palermo , Argentina .

Distribution. Widespread in Argentina (provinces Buenos Aires, La Pampa, Córdoba, Santa Fe, Entre Ríos, Corrientes and Misiones), Uruguay (Departamentos Colonia, Rio Negro, Paysandú, Rivera, Cerro Largo, Treinta y Tres) and southern Brazil (Rio Grande do Sul State) ( Fig. 3 ).

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.