Parabalta bicornis ( Gervais, 1849 ) Acosta, 2025

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 : 200-205

Parabalta bicornis ( Gervais, 1849) comb. nov., revalidated urn:lsid:zoobank.org:act:3353AFE9-7113-4E68-ADD8-01EEF8CFAD5C

Figs. 1A–F , 2A–C

Gonyleptes bicornis Gervais 1849: 21 ; Butler 1873: 114 (species list). Type (s) unknown.

Gonyleptes acanthops Gervais 1854 (in part): Atlas, Arachnídeos , pl. 1, fig. 4b—NEC Gervais, 1849: 22 (description corresponds to G. acanthops ; only fig. 4b to G. bicornis ).

Gonyleptes planiceps : Gervais 1854: Atlas, Arachnídeos , pl. 1, fig. 10—NEC Gervais 1849: 24 (description corresponds to the true G. planiceps ; fig. 10 to G. bicornis ).

Lycomedes (?) planiceps [sic]: Sørensen 1902: 21 (in part?—he draws attention to the mismatch between description and fig. 10 of Gervais, 1849: ‘Descriptio enim et figura, a Gervais datae, nullo modo congruunt’ —unable to identify the species).

Lycomedes planiceps : Roewer 1913: 127, 134, figs. 60, 61 (misidentification, based on a MNHN specimen he wrongly believed to be Gervais’ type —it matches fig. 10 of Gervais 1854!) .

NEC Lycomedes bicornis : Sørensen 1902: 20 [‘descriptio G. bicornis fìguris 4 congruit’ = he wrongly assumes that figs ‘ 4♂, 4♀ and 4b’ of Gervais 1854 refer to L. bicornis ]; Roewer, 1913: 136, fig. 62 [species considered “unsichere Art”; follows Sørensen 1902, and reproduces fig. 4♂ of Gervais 1854].

Lycomedicus planiceps : Roewer 1923: 442, 445, figs. 559, 560 (misidentification, probably based on the same specimen, now in Coll. Roewer—although the supposed Gervais’ type from MNHN is still cited, both ‘specimens’ may be the same); Soares & Soares 1954: 271 (in part; they adopted Roewer’s criteria); Cekalovic 1968: 8 (in part; wrong date), 1976: 26 (in part; some mistaken localities), 1985: 19 (in part); Acosta 1996a: 224 (SMF, RI/795).

Lycomedicus bicornis : Canals 1936: 69 [species list]; Cekalovic 1968: 8; 1985: 18 (in part)—NEC Roewer 1923: 445, fig 561 [species listed as “unsichere Art”; figs 4, 4a, 4b of Gervais 1854 are wrongly assumed to correspond to L. bicornis ]; Soares & Soares 1954: 270 [the same about figs 4, 4a, 4b of Gervais 1854].

Sadocus bicornis : Kury 2003: 191 (in part, refers to figs 4, 4a–b) [proposal of new combination].

Sadocus asperatus : Pessoa-Silva et al., 2021: 104 (in part, refers to figs 4, 4a–b) [synonymy proposal].

Type material. Neotype ♂ ( MACN-Ar 46511 ): CHILE, Coquimbo Region, Choapa Province, Cuesta Cavilolén , 30 km NE Los Vilos, 12 November 1987 (E.A. Maury leg.), hereby designated.

Qualifying conditions for neotype designation (as required by the ICZN, Art. 75.3). This designation is purposed to guarantee the nomenclatural stability of the revalidated binomen Gonyleptes bicornis , considering that the taxon was repeatedly misidentified by all authorities for more than 170 years, and also affected the taxonomic knowledge of other species treated by Gervais (1849). The analysis of the most significant interpretations (e.g., Sørensen 1902, Roewer 1913, Pessoa-Silva et al. 2021) is given in detail above, where the ‘exceptional need’ for a neotype is endorsed. The diagnostic features on which the preceding assessment of the description and figures of Parabalta bicornis focused (see e.g., Tables 2–3) are readily recognizable in the material studied and in the redescription below, thus giving ‘evidence that the neotype is consistent with what is known of the former namebearing type from the original description’, as ruled in Art. 75.3.5. Gervais (1849) did not provide a precise original locality, but merely stated ‘it is found in humid places of the [Chilean] Republic’. However, it is worth noting that one of Claude Gay’s many exploratory trips across the country took him very close to the modern records of P. bicornis in southern Coquimbo (cf. Sagredo Baeza 2010: xix, xxiii and Fig. 3 ). No author (not even Gervais 1849) stated the existence of types or the location of original specimens of G. bicornis , and my own searches in European collections ( NHMUK, MNHN, NHMW, SMF, ZMC, among the most relevant) also resulted negative. The neotype is lodged in MACN-Ar, an outstanding biodiversity collection in South America (fulfilling Art. 75.3.7.).

Other materials studied. CHILE, Coquimbo Region, Choapa Province: Cuesta Cavilolén, 30 km NE Los Vilos, 12 November 1987 (E.A. Maury), 7 ♂, 2 ♀, 2 juv. ( MACN-Ar 46512), 1 ♂, 1 ♀ ( CDA 000.069); same loc., 7 November 1988 (E.A. Maury), 1 ♂, 2 ♀, 2 juv. ( MACN-Ar 46513); Quebrada Playa Agua Dulce, 46 km N Los Vilos, 5–6 November 1988 (E.A. Maury), 1 ♂, 1 ♀ ( MACN-Ar 46514); “Chile”, 1 ♂ “ Type ex Mus. Paris” ( SMF RI/795) - Lycomedes planiceps det. Roewer 1913), not a type indeed ( Acosta 1996a).

Type locality. Cuesta Cavilolén , 30 km NE Los Vilos, Province Choapa, Chile (ca. 31°46.26’S 71°18.95’W) .

Distribution. Chile, Coquimbo Region: Choapa Province. Records of this species represent the northernmost ones in the genus ( Fig. 3 ).

Diagnosis and comparisons. Male Parabalta bicornis comb. nov. are recognized by having a bifid apophysis on CxIV; armature of TrIV consisting of an apical prodorsal finger-like apophysis pointing upwards, and a small ax-like one on the prolateral side; a row of small apophyses following the dorsomedial one on FeIV; two large acute ventral apophyses on patella IV, and the absence of large ventral apophyses between the basal one and the distal group on TiIV. A detailed comparison with Parabalta reedii + P. cristobalia is shown in Table 4 (these two nominal species are closely allied, if not synonyms, so they are entered together in the table).

Redescription. Measurements and meristics. DS length: ♂ 7.0–8.0 mm (mean= 7.5 mm, n= 11), ♀ 7.0–7.9 mm (x= 7.5 mm, n= 6). Detailed measurements of the neotype ♂ and a selected ♀: Table 5. Tarsal formula: ♂ 6:8–9:6:6 (neotype with 6:8:6:6), selected ♀ 6:7–8:6:6.

Coloration in ethanol 70%. General color yellowish to brownish cinnamon, CxIV, TrIV and FeIV of males darker (somewhat more reddish).

Males: Dorsum. DS type γR (gamma rotund, coda unrecognizable, embodied by the large, round mid-bulge; Fig. 1A ). Ocular mound with a pair of tall, acute apophyses ( Fig. 1E ). Front border with conic granules in a row, scattered on the frontal hump, which is lower than the ocular mound ( Fig. 1F ); scutum margin with a row of small round granules from the ozopore up to constriction 1, then vanishing towards area I. Lateral areas elevated, practically smooth beyond area I. Otherwise DS unarmed ( Fig. 1A ), faintly rugose on carapace, smooth and shiny on the rest; area I divided, areas I–IV entire. Area V, FT and dorsal anal plate have a row of flat, very faint granules, the paramedian pair slightly larger than the rest (still flat). In some specimens there is a pair of tiny and inconspicuous paramedian granules on areas III–IV as well.

Venter ( Fig. 1B ). Posterior margin concave; genital and stigmatic segments delimited by faint tegumentary borders, better defined in small specimens and difficult to see in larger ones (as in the Neotype); the genital part, smooth, depressed and lighter in color. Free sternites almost smooth, with row of minute granules, except for the last sternite and the ventral anal plate, which bear round granules, larger on the laterals.

Chelicerae. Unarmed, finely rugulose, posterior side of bulla slightly granulous.

Pedipalps. Weak, dorsal tegument tenuously rugose. Ventral setigerous tubercles on Tr (one) and Fe (one basal, followed by a row of blunt ones); Fe with a small medial subapical spine. Pedipalp spination: LAT: Ti i_[Ii•], Ta IiIi – MED: Ti IiIi, Ta IIi.

Legs I–III. Unarmed, tegument finely granulous; only a few large proventral apical granules on FeIII.

Leg IV. CxIV ( Figs. 1A–C ) smooth to very finely granular, with a strong prolateral apophysis directed diagonally (back– and sideward); it is bifid-tipped, with dorsal branch longer, acute and posteriorly inflected, ventral branch tuberous; on the same ridge as the latter, a ventro-medial basal tuberosity. Minute conic retrolateral apophysis, not easily discernible in some larger specimens.

TrIV ( Figs. 1A, C ) elongated, armed with a strong apical prodorsal apophysis, pointing upwards, S-curved medially and anteriad; a small ax-like prolateral apophysis on the proximal third; retrolateral surface granulous.

FeIV ( Figs. 1A–C ) granulous, gradually wider from base to apex; substraight with a slight, abrupt inflection between the first and second third. One large acute apophysis, ventro-proximal, inclined to the median line. A prodorsal row limited to the basal third formed by one (single or bifid) or two upwards pointing, moderate apophyses followed by tall granules. Upon the femur inflection, a large retrodorsal apophysis, somewhat shifted medially and slightly diagonal, either horizontal or gently curved downwards; it is continued after a small gap by a variable row of decreasing apophyses, which turn into granules up to an apical, small conic apophysis. Along the distal two thirds of FeIV, pro- and retroventral rows of tubercles to small apophyses, the former ending in a large apical unciform apophysis, the latter in a smaller one.

PaIV, ventral side with blunt grains and two apicoventral acute apophyses, the largest one placed on the midline.

TiIV sigmoid in lateral view (more accentuated and more slender in larger specimens), it bears a strong basal apophysis, slanted medially, and a distal group of three apophyses arranged in a triangle; in between 2–3 minute intermediate tubercles may exist, otherwise there is a large smooth gap ( Figs. 1C–D ).

MeIV straight, smooth, fairly thicker than tarsus.

Penis ( Figs. 2A–C ). Trunk subterminally swollen (wider than high), with glans articulated in the same axis. VP sub-rectangular, front margin straight; it is quite flat in lateral view. Lateroapical group of 3–4 macrosetae C. Basal group displaced to the swollen sector of trunk, consisting of two large setae (A1–A2) arranged longitudinally and a small B1 more ventrally. D1 and E1–E2 minute. Glans with ‘columnar’ look, it has membranous expansions on the sides; a thick, finger-like DPG curved towards the stylus, as diagnostic for the genus ( Acosta 1996b). Stylus simple and straight, diagonal, devoid of any spination; VPS of similar length and orientation, its tip abruptly bent downwards in a spiny flat expansion.

Variability of ♂ (condition found in the neotype marked as *N). FeIV (n=20): Sub-basal, prodorsal armature with a single conic apophysis (11/20, *N- left), two contiguous (3, *N- right), one bifid (5) or several fused in a tuberous stem (1); the brief row of smaller apophyses/tall granules that follows distad is highly variable, decreasing in size either in regular (*N) or irregular fashion; only rarely (3/20) a few conic grains proximal to the large apophysis. FeIV (n=20): Large retrodorsal apophysis, either slender (16/20, *N), very thick (2) or smaller than the row that follows (2); it is normally simple (18, *N) or may bear a small subapical branch (2); there are seldom (6/20, *N-right) one or more acute granules basal to it. TiIV (n=20): gap between ventro-basal and distal apophyses either smooth (14/20) or with 2–3 vestigial tubercles (6/20, *N). Some specimens examined of P. bicornis , like SMF RI/795 though likely not that depicted in fig. 10 (Gervais 1854), bear a pair of minute, quite imperceptible paramedian granules on areas III–IV, easier to discover in lateral view (in dorsal view they may appear not much as lighter dots). In *N these granules are overly undersized, only visible with DS completely dried out ( Fig. 1A ). In Roewer’s (1913) redescription and illustration of Lycomedes planiceps the development of those granules was overstated, showing them as conic tubercles. This was much probably to justify the inclusion of the species in Lycomedes (later Lycomedicus ), which was diagnosed with area III ‘armed’.

Females: DS type α-K (alpha-keyhole, coda with divergent sides), unarmed. Lateral areas with a marginal row of round flat granules up to constriction 2. Granules on area V and FT larger than in male; on FT-I a pair of larger paramedian flat granules, on FT-II–III they become small acute apophyses (larger on FT-III). CxIV with small acute prolateral apophysis, diagonally divergent; a small retrolateral one hinders the coxal base to completely fuse with the stigmatic segment, leaving a gap. Stigmatic and genital segments clearly delimited by a tegumentary ridge. Free sternites with a row of round granules, larger than in male, especially on the laterals. TrIV with retrolateral side covered by granules. FeIV slightly curved, granose, with a small apical proventral apophysis. PaIV unarmed; TiIV straight, club-shaped, with a minute apical retroventral, spine-shaped apophysis.

On the publication dates. Following the current use, the date printed on the front page of volume 4 of the Historia Física y Política de Chile (1849) is here accepted as valid for Gonyleptes bicornis . It should be warned that volumes were not printed and delivered to subscribers in full; instead, tomes were issued in parts as soon as these were ready, meaning that every single part has its own effective date of publication. Parts are what Gay called ‘entregas’ (=livraisons, releases), consisting of a number of successive gatherings under a temporary cover, intended to be bound later in the final volume. Signatures, i.e., the marks printed to aid the binder in arranging the gatherings in the correct order, can be recognized on the bottom of the first page of each sheet. As a rule, covers of entregas were removed upon binding, save a few exceptional cases in which they were conserved ( Johnston 1941). Almost all zoological volumes consisted of four entregas, except for volumes 2 and 4, each formed by three (N. Evenhuis, unpublished, in litt. 2024). For the botanical part, Johnston (1941) determined that the date on the title page on each volume represents the year when the printer began to work on it, not necessarily the date in which it became available; anyway, in most cases the printed year coincides with the date of at least the first entrega ( Johnston 1941). This procedure can be generalized to the zoological part as well ( Evenhuis 2015). The description of Gonyleptes bicornis , published on pages 21–22, falls within the first entrega of volume 4, which spans from page 1 to 188 and comprises 12 gatherings (N. Evenhuis, in litt. 2024). Thus, in this case we can be confident that the date printed on the front matter (1849) is that of G. bicornis ; the year is also endorsed by dates extrapolated from other sources by N. Evenhuis (unpublished, in litt. 2024).

Dating of plates proved to be especially challenging ( Johnston 1941). They were also issued individually, to be bound together at the end, making up the two volumes of the Atlas ( Sagredo Baeza 2010) . Although plates were delivered together with the entregas, they were not necessarily synchronous with their reciprocal part of text ( Johnston 1941). For example, the very first entrega, corresponding to the historical section, was delivered in 1844 along with two zoological plates ( Sagredo Baeza 2010), whereas the zoological text itself started being issued just in 1847. As the precise date of plates remains unknown (N. Evenhuis, in litt. 2024), the only choice is to adopt the date printed on the title page of the Atlas (1854). It has been emphasized that the Atlas reveals several inconsistencies, with some copies available in libraries lacking one or more plates, or containing duplicate ones; in some instances, incongruence between the reference in the text and the labels on the plate has been detected ( Stuardo Ortiz 1953), as is the case of Gervais’ (1854) ‘Arachnideos N° 1’. Readers should be also aware of the existence of a second, cheaper edition of the whole work, issued in 1866, in which all plates were printed in black, i.e., no figure was colored.

Figures

FIGURE 1. Parabalta bicornis (Gervais, 1849) comb. nov. A–F: Neotype ♂ (MACN-Ar 46511). A. Dorsal scutum, free tergites, coxae IV (arrow: ventro-medial tuberosity at the base of coxal apophysis), right trochanter and femur IV, dorsal view. B. Venter, with ventral view of coxae IV, genital and stigmatic segments, free sternites, ventral anal plate, right trochanter and femur IV. C. Right coxa, trochanter, femur, patella and tibia IV, prolateral view. D. Right patella, tibia, metatarsus and tarsus IV, retrolateral view. E–F. Ocular mound, E. posterior view, F. lateral view with anterior border of prosoma and frontal hump. Scale lines: 2 mm.

FIGURE 2. Parabalta bicornis (Gervais, 1849) comb. nov., distal end of penis (MACN-Ar 46514). A: dorsal view; B: lateral view; C: detail of VPS (rotated). Scale lines: 0.1 mm.

FIGURE 3. Records of Parabalta bicornis (Gervais, 1849) comb. nov. (red dots), along with other localities studied of genus Parabalta in central Chile (blue dots). Administrative Regions (thick solid boundaries) are labeled on the right. Only relevant provinces are given flags: Choapa, Petorca, Quillota (QUILL.), Los Andes, Santiago (SANT.). Color gradient: elevation below (light brown) and above (darker brown) 1000 m a.s.l. Gray: major urban areas. Inset: location of the represented area in Chile.