Gonyleptes bicornis, Gervais, 1849

Acosta, Luis E., 2025, Deciphering a Chilean harvestmen enigma: what is Parabalta bicornis (Gervais, 1849) comb. nov. (Opiliones: Gonyleptidae: Pachylinae), Zootaxa 5563 (1), pp. 193-208 : 195-197

Revalidation of Gonyleptes bicornis

Pessoa-Silva et al. (2021: 105) proposed the synonymy of Gonyleptes bicornis under Sadocus asperatus , seemingly based on Roewer (1913) (they cite ‘fig. 4a–b’ in their synonymy; also a non-existing ‘fig. 4–4b’ in the entry for Sørensen 1902). Pessoa-Silva et al. (2021) based their conclusion on both the original description and the supposed drawings of G. bicornis , i.e., adopting the prevailing usage of considering Gervais’ (1854) fig. 4 as referable to this species. As key features from the original description of G. asperatus (cf. Gervais 1847), to support the synonymy Pessoa-Silva et al. (2021) mention (a) ‘the spines on the free tergite’, (b) ‘the two apical apophyses on the TrIV’, and (c) ‘uneven spines in the inner part of the “leg” (referring to FeIV)’. The comparison between the descriptions of G. asperatus (both the original one, Gervais 1847, and the redescription of Gervais 1849) and that of G. bicornis ( Table 2) yielded the following outcomes:

(a) Spines on free tergites are described only for G. asperatus ; just weak tubercles exist in G. bicornis .

(b) The description of Gervais (1847) of G. asperatus does not give enough detail about apophyses on TrIV, and only some resemblance could be extrapolated if Gervais’ (1854) fig. 9 and the description of G. bicornis were taken into account.

(c) About FeIV, Gervais’ (1847) description of G. asperatus and Gervais’ (1854) fig. 9 agree in the inner border being armed with strong apophyses; but comparison with G. bicornis is inconclusive. Incidentally, Pessoa-Silva et al. (2021) misinterpreted the word ‘leg’ (‘pierna’ in the Spanish text) assuming that Gervais (1849) referred to the femur, when the tibia was actually meant. As a matter of fact, apophyses on ‘leg’ (tibia) IV provide the best diagnostic feature to assess that G. bicornis is a member of Parabalta . This feature is only indicated in the description of G. bicornis and clearly shown on Gervais’ (1854) fig. 10.

Many items exhibit a decided mismatch between the descriptions of G. asperatus and G. bicornis ( Table 2); in other features comparison resulted inconclusive (?), and only the paired armature on the ocular mound and the bifid apophysis of CxIV look similar in both (by the way, both character states are actually quite widespread in the family). In sum, G. bicornis did not prove to be a junior synonym of G. asperatus , and has to be revalidated and transferred to Parabalta instead.

bicornis . Features invoked by Pessoa-Silva et al. (2021) to support their synonymy proposal are underlined.