Introduction

The family Stynopsidae S͕ørensen, 1932, currently contains 26 genera and 76 described species, distributed mainly in Mexico. The family is composed by two subfamilies: Stygnopsinae S͕ørensen, 1932 and Karosinae Cruz-López & Francke, 2017, the latter with nine genera and 28 species (Cruz-López, 2021; Cruz-López & Francke, 2015, 2017, 2019b, 2020).

Among karosine harvestmen, the genus PotosaGoodnight & Goodnight, 1947 is one of the most enigmatic taxa. It comprises three species; females are known only in Potosa reddelliCruz-López & Francke, 2015. Its geographical distribution spans approximately 40 Km in the central portion of the Huasteca Region, between San Luis Potosí and Hidalgo states, Mexico. Members of this genus are distinguished by the synapomorphy of presence of ventral glandular opening in the middle portion of swollen metatarsus I in males (Cruz-López & Francke, 2015; Cruz-López, 2018).

The taxonomic history of the genus, although brief, has been inconstant over the years, going from being part of the Phalangodidae, later considered a synonym of the genus Karos Goodnight & Goodnight, 1944, and finally transferred to its current family placement within Stygnopsidae, until its revalidation and current taxonomic position (Goodnight & Goodnight, 1953; Cruz-López & Francke, 2015; Cruz-López, 2018).

Between 2011 and 2015, Cruz-López (2018) conducted several field trips to collect fresh material of the type species, as well as additional material of Potosa elsantoCruz-López, 2018 in their respective localities where both species had been reported. Despite this, only two males of P. elsanto were collected during this period, demonstrating that this group is one of the most difficult to obtain in the field using conventional methods for harvestmen studies.

During the revision of the Opiliones deposited at Collection of Arachnology (CARCIB), from the Centro de Investigaciones Biológicas del Noreste, S. C. (CIBNOR), I found a vial with two males and one female of a new species of Potosa, which is described herein.

Materials and methods

Types are deposited at CARCIB, CIBNOR, La Paz, Baja California Sur, Mexico. Photographs were taken using a Color CMOS C-Mount Microscope Camera attached to a Jewelry Zoom Stereo Microscope, using the software AmScope v. 3.1. Male genitalia photos were taken using the same camera but attached to compound microscope Iroscope U-THC. Photographs at different depths were staked using the software Helicon Focus v. 6.7.1., male genitalia drawings were handmade, later vectorized using Concepts App for IOS v. 5.8.7. Morphological nomenclature follows Cruz-López & Francke (2015, 2017), dorsal scutum nomenclature according to Kury & Medrano (2016), pedipalpal armature follows Acosta et al. (2007), and macrosetal nomenclature of male genitalia according to Kury & Villarreal (2015), with specific modifications to Stygnopsidae proposed by Cruz-López & Francke (2017).

Results

Potosa pisaflores Cruz-López, sp. nov.

urn:lsid:zoobank.org:act:234367A2-4DC8-4499-BC89-78A09CE16739

(Figs. 1-3)

Type locality: Mexico: Hidalgo, municipality of Pisaflores, Cueva del Caracol, 1.5 Km SE from El Caracol (21.2083°N, -98.9558°W, 880 masl).

Type material. Male holotype (CARCIB-Op-H-0001) with red label: Mexico: Hidalgo, municipality of Pisaflores, Cueva del Caracol, 1.5 Km SE from El Caracol (21.2083°N, -98.9558°W, 880 masl), May 25, 2018, Cols. A. Valdéz, P. Solís, A. Cabrera, J. Valerdi and I. Navarro. Male and female paratypes (CARCIB-Op-Pa-0001) with yellow label, with the same data as the holotype.

Etymology. Toponymic in reference to the municipality where this species was collected.

Diagnosis. Potosa pisaflores sp. nov., is recognizable by: ocularium with sharp medium spine (Fig. 1), distitarsus II of leg II with similar length as the distitarsus I, leg II with 7/8 tarsomeres (Fig. 2B), femur IV straight and not swollen apically, base of pars distalis swollen in a dorsoventral view, and presence of two pairs of additional macrosetae E (Fig 3).

Figure 1
Habitus of Potosa pisafloressp. nov. (A) and (B) dorsal and lateral, holotype; (C) dorsal female paratype. Scale bar: 1.5 mm for all figures.

Figure 2
Legs, chelicera and pedipalp of male paratype of Potosa pisafloressp. nov. (A) retrolateral view of leg I, (B) retrolateral view of metatarsus and tarsus II, (C) frontoventral view of chelicera, (D) ventromesal view of pedipalp. Arrow on (A) indicates the ventral glandular opening. Roman numerals in (B) indicates the number of each tarsomere. Ellipse in (C) indicates the cheliceral comb. T1-T3 on (D) indicate the major setiferous tubercles on tibia. Scale bars: (A) = 2.0 mm, (B) = 1.5 mm, (C) = 0.5 mm, (D) = 1.0 mm.

Figure 3
Penis of male paratype of Potosa pisafloressp. nov. (A) dorsal, (B) ventral. Macrosetal groups are indicate on each figure. Scale bar: 0.1 mm for both figures.

Description. (Male holotype CARCIB-Op-H-0001). Scutum length: 3.0 mm. Scutum width in the middle portion: 2.5 mm. Color reddish yellow in 80% alcohol, uniform throughout the entire body, tarsi lighter.

Dorsal scutum (Fig 1). Gamma type, with median bulge swelling, well-marked, covering almost the entire length of the lateral margins. Constriction I rounded and deep, constriction II softly marked, contiguous with the coda. The central portion of lateral margins at level of mesotergal area I with the presence of a pair of rounded lateral clear areas, just over the area of lateral channels. Prosoma rectangular shape, slightly wider at the level of ozopores. Ocularium in the middle of prosoma, small, triangular shaped, with an apical spine about 1.5 times higher than the ocularium, tip slightly pointing backward. Frontal bulge of prosoma barely developed. Mesotergum with five areas, boundaries between them shallow. Area I larger than the rest, areas II, III, and IV with similar size. Area I with a transversal row of few small spiniform tubercles, forming an irregular row. Mesotergal areas II and III with a transversal row of few spiniform tubercles, the central ones prominent, with the middle tubercle of the area III the most prominent. Mesotergal area IV with only a transversal row of few tubercles. Free tergites with a transversal row of spiniform tubercles, similar to those on the dorsum; lateral apices with rounded clear lateral areas, similar to those on the middle portion of lateral channels.

Chelicera (Fig. 2C). Sexually monomorphic, small, bulla beak, fixed cheliceral finger with two small teeth in the middle, movable finger with two irregular median teeth. Fixed finger with ventral comb.

Pedipalp (Fig. 2D). Femur rectangular in cross section, slightly curved; ventrally with a row of five spiniform setiferous tubercles, the two basalmost being larger than the rest. Femur with a long setiferous tubercle in the meso-apical surface. Patella cylindrical, with few and small tubercles dorsally; with two long setiferous tubercles on mesal face. Mesal face of tibia with the three typical setiferous tubercles (T1-T3), between T1 and T2, with additional short setiferous tubercles as follows IiIi (3>1=4>2); ectal margin with only two major setiferous tubercles, T1 and T3: ii (1=2). Tarsus with three setiferous tubercles on both margins. Pedipalpal claw shorter than the tarsus.

Legs (Figs. 2A, B). All legs are slender and covered by small tubercles not arranged in rows, tubercles present from trochanters to metatarsi. Tarsi covered only by small setae. Metatarsus I swollen at the base, with the typical glandular opening in the middle, dome-shaped. Distitarsus I-III (tarsal segments VI-VIII) similar in size, not swollen, distitarsus II slightly longer than I, and disitarsus III slightly longer than II. Femur IV covered by small spiniform tubercles, slightly pronounced on the ventral side, not forming rows; femur slightly curved in the middle. Tarsal count: 4(2):7/8(3):6:6.

Penis (Fig. 3). Pars distalis flattened dorsoventrally, apical portion of the flimsy lamina slightly rolled ventrally, with the margin slightly dentate near the apices; at the base, the pars distalis is swollen, at level of the macrosetae A. The follis is exposed, originates from the middle of pars distalis, at level of the macrosetae C3. Follis long, apically with two lateral lobes, interno-apical surface of it covered by minute spiniform projections. Stylus originated from the internal follis and with apical bristles. With three pairs (C2 absent on one side) of macrosetae C located laterally on the pars distalis, at the same level at the follis. With a pair of macrosetae A in the basalmost portion of par distalis, just on the swollen area. Two pairs of macrosetae D located at the lateral sides of the follis, in a longitudinal axis respect to the penis. With four pairs of small macrosetae E, the typical E1 (absent on one side) and E2 located as follows: E1 between C1 and the apical margin; and E2 between C1 and C2. Additional macrosetae E3 between C2 and C3 and, the basalmost pair E4 in the swollen portion, at the same level of the macrosetae A.

Female (Fig. 1CC. The unique specimen is very similar to the male, with the absence of the ventral glandular opening on metatarsus I. Tarsal count: 4(2):8(3):6:6.

Natural history. The specimens were collected under rocks, in the middle section of the cave (Fig. 4B).

Geographical distribution. This species is endemic, only known from the type locality (Fig. 4).

Figure 4
(A) Panoramic view from the entrance of the Cueva del Caracol. (B) Photo of entrance of the cave from the first 50 meters inside. Both photographs courtesy of A. Valdéz-Mondragón.

Discusion

Although only eight male specimens are known of the genus, it is interesting that they exhibit irregularities or asymmetries in the number of pairs of penial macrosetae. In the case of P. pisafloressp. nov., there are incomplete pairs of macrosetae C2 and E1. The remaining species also exhibit incomplete pairs, which are not due fractures or breaks during handling of the male genitalia. This condition is not common in other stygnopsids, are not even reported frequently among Laniatores.

The presence of sexually dimorphic glandular openings on legs in Laniatores is generally related to intraspecific chemical communication; however, in the great majority of species that possess them, the behavior mechanisms are unknown (Willemart et al., 2010). These kinds of glandular openings generally are associated with some enlarged or swollen portion on some segments of legs. Among stygnopsid harvestmen, a few genera have some portions of their legs enlarged, suggesting that there are possible glandular openings in the respective segments. In addition to Potosa, two genera with modifications are Mexotroglinus Šilhavý, 1977 and HuastecaCruz-López & Francke, 2015, with apical tibia II, and patella with basal tibia II swollen, respectively. Cruz-López & Francke (2017, 2019a), showed that those modifications on Mexotroglinus and Huasteca are not associated with any kind of glandular opening, and it is possible that they are not related with chemical communication.

As mentioned above, Potosa is the most enigmatic genus of the family, with very few specimens of the four species known. However, they can be easily recognized and diagnosed from each other, and identification key is provided below.

Updated key to the species of Potosa based on males, modified fromCruz-López (2018)

1. Ocularium without medium spine ………..……………..…… Potosa redelliCruz-López & Francke, 2015

1’. Ocularium with medium spine ..………………………………………………...…………………………………………….. 2

2. Distitarsus II of leg II noticeably longer than distitarsus I ………………... P. elsantoCruz-López, 2018

2’ Distitarsus II of leg II with similar length as distitarsus I …………………………………………..….................. 3

3. Leg II with 7/8 tarsomeres, base of pars distalis swollen, with two pairs of additional macrosetae E … …………………………………………………………………………………………………………. Potosa pisaflores sp. nov.

3’. Leg II with 5 tarsomeres, base of pars distalis not swollen, with one pair of additional macrosetae E … ………………………………………………………………………………….. P. dybasiGoodnight & Goodnight, 1947

Acknowledgments

I thank to Alejandro Valdéz-Mondragón (CIBNOR) for the loan of the specimens for the description. Specimens were collected under the Scientific Collector Permit FAUT-0309 from the Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT), Mexico, granted to A. Valdez-Mondragón. The financial support was possible through the project of Ciencia Básica 2016 No. 282834, granted by the Consejo Nacional de Ciencia y Tecnología (CONACYT), currently the Secretaría de Ciencia, Humanidades, Tecnología e Innovación (SECIHTI), Mexico.

Literature cited

Acosta, L. E., Pérez-González, A., Tourinho, A. L. (2007) Methods for taxonomics study p. 494-505. In: R. Pinto-da-Rocha, G. Machado, G. Giribet (Eds.). Harvestmen: The Biology of Opiliones. Massachusetts and London: Harvard University Press, USA.

Cruz-López, J. A. (2018) Potosa elsanto sp. nov., the third species of the genus Potosa (Opiliones: Stygnopsidae: Karosinae). Revista Mexicana de Biodiversidad, 89, 79-86. https://doi.org/10.22201/ib.20078706e.2018.1.2074

Cruz-López, J. A. (2021) Two new genera and two new species of troglobitic harvestmen of Stygnopsidae (Opiliones, Laniatores, Gonyleptoidea) from Oaxaca, Mexico, with notes on selected morphological characters. Zoosystema, 43, 101-112. https://doi.org/10.5252/zoosystema2021v43a5

Cruz-López, J. A., Francke, O. F. (2015) Cladistic analysis and taxonomic revisión of the genus Karos Goodnight & Goodnight, 1944 (Opiliones, Laniatores, Stygnopsidae). Zoological Journal of the Linnean Society, 175, 827-891. https://doi.org/10.1111/zoj.12299

Cruz-López, J. A., Francke, O. F. (2017) Total evidence phylogeny of the North American harvestman family Stygnopsidae (Opiliones: Laniatores: Grassatores) reveals hidden diversity. Invertebrate Systematics, 31, 317-360. https://doi.org/10.1071/IS16053

Cruz-López, J. A., Francke, O. F. (2019a) New species of the cave-dwelling genus Huasteca (Opiliones: Stygnopsidae: Karosinae), from Northern Oaxaca, Mexico, with a SEM survey of the sexually dimorphic areas on legs and structures related to chelicera in the genus. Journal of Natural History, 53, 1451-1464. https://doi.org/10.1080/00222933.2019.1657194

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Cruz-López, J. A., Francke, O. F. (2020) Two new genera of epigean harvestmen (Opiliones, Stygnopsidae) from Oaxaca, Mexico, with an identification key for the stygnopsine genera. Zootaxa, 4748, 431-454. https://doi.org/10.11646/zootaxa.4748.3.2

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Kury, A. B., Villarreal, O. (2015) The prickly blade mapped: establishing homologies and a chaetotaxy for macrosetae of penis ventral plate in Gonyleptoidea (Arachnida, Opiliones, Laniatores). Zoological Journal of the Linnean Society , 174, 1-46. https://doi.org/10.1111/zoj.12225

Kury, A. B., Medrano, M. (2016) Review of terminology for the outline of dorsal scutum in Laniatores (Arachnida, Opiliones). Zootaxa , 4097, 130-134. https://doi.org/10.11646/zootaxa.4097.1.9

Willemart, R. H., Pérez-González, A., Farine, J. P., Gnaspini, P. (2010) Sexually dimorphic tegumental gland openings in Laniatores (Arachnida, Opiliones), with new data on 23 species. Journal of Morphology, 271, 641-653. https://doi.org/10.1002/jmor.10822

Notes

Author notes