Two new genera and two new species of troglobitic harvestmen of Stygnopsidae (Opiliones, Laniatores, Gonyleptoidea) from Oaxaca, Mexico, with notes on selected morphological characters

ABSTRACT Two monotypic and troglobitic genera of harvestmen are described from caves in Oaxaca, Mexico: The Karosinae Cruz-López & Francke, 2017 Brujita chapulapa n. gen., n. sp. and the Stygnopsinae Sørensen, 1932 Toojah cimutaa n. gen., n. sp., both based on males only. Also, based on the examination of the male holotype of Hoplobunus planus Goodnight & Goodnight, 1973, the new combination is proposed: Mictlana plana (Goodnight & Goodnight, 1973) n. comb., proposing an emended diagnosis for Mictlana Cruz-López & Francke, 2015, including an analysis of the dilemma of the position of the ocularium and observations on selected homoplastic characters. Finally, on the regard of troglobitic stygnopsids, a review of the exclusive morphological traits exhibit by some representatives of the family is addressed, discussing on the putative synapomorphies of each subfamily.


INTRODUCTION
Mexico has one of the most diverse troglobitic faunas due to its extensive and complex cave systems throughout the entire territory (Reddell 1981). In a review of cave fauna from Mexico, Guatemala and Belize, Reddell (1981) reported at least 279 troglobitic metazoan especies in these countries, the great majority in Mexico. Regarding Opiliones Sundevall, 1833, Kury & Cokendolpher (2000) supposed that almost 20% of the Mexican fauna are troglobites or troglophiles, and then 46% of total undescribed species in the genera Hoplobunus Banks, 1900and Karos Goodnight & Goodnight, 1944, [both sensu Goodnight & Goodnight (1953] are predominant troglophilic or troglobitic. The current knowledge on the systematics of Stygnopsidae Sørensen, 1932 has been studied using a phylogenetic framework (Cruz-López & Francke 2015, 2017. These studies clarified the phylogenetic position of many troglobitic and troglophilic taxa previously recognized as part of Hoplobunus and Karos (Cruz-López & Francke 2015, 2017. Troglobitic stygnopsids exhibit different degrees of troglomorphisms, i.e. depigmentation of cuticle, elongation of appendages, elevated tarsal count and reduction or total lack of eyes (Table 1). However, only six species are completely blind: Chinquipellobunus madlae (Goodnight & Goodnight, 1967), Hoplobunus planus Goodnight & Goodnight, 1973, Mexotroglinus sbordonii Šilhavý, 1977, Mictlana inops (Goodnight & Goodnight, 1971, Serrobunus paulbryanti Aguiñaga & Cruz-López, 2019 and Troglostygnopsis anophthalma Šilhavý, 1974, calling attention that all of them belong to different genera and both Mexotroglinus Šilhavý, 1977 andTroglostygnopsis Šilhavý, 1974 are monotypic. In the present contribution, two new and monotypic genera of eyeless stygnopsids are described: Brujita chapulapa n. gen., n. sp. and Toojah cimutaa n. gen., n. sp. from different caves in Oaxaca state, Mexico. These new genera can be recognized from other troglobitic stygnopsids mainly by combination of character of external morphology and male genitalia. Based on the revision of the holotype of H. planus, the new combination Mictlana plana (Goodnight & Goodnight, 1973) n. comb. is proposed, with an emended diagnosis of the genus Mictlana Cruz-López & Francke, 2015. Finally, a discussion on the putative synapomorphies for both subfamilies and a discussion of some conflictive characters as the correct ocularium position in Mictlana and Brujita n. gen. are addressed.

MATERIAL AND METHODS
Type material examined in this work are deposited in two collections (see Abbreviations). Male genitalia were prepared for scanning electronic photographs (SEM) following the procedure described in Acosta et al. (2007). SEM photographs were taken in a Hitachi S-2460N microscope in the Laboratorio Nacional de Biodiversidad (LaNaBio), in the Instituto de Biología, UNAM (IB-UNAM). Images were assembled into plates using Photoshop CS5. Nomenclature of scutum follows Kury & Medrano (2016), pedipalpal armature follows Acosta et al. (2007) with additional annotations on the armature taken from Aguiñaga & Cruz-López (2019), for macrosetae and microsetae on penis according respectively to Kury & Villarreal (2015) and Kury (2016). Additionally, I will adopt the term flimsy lamina referring to the undeveloped ventral plate of penis, which is a synapomorphy of Stygnopsidae according to Cruz-López & Francke (2017). emended diAgnosis. -Troglobitic karosins, eyeless, with two dorsal lobes on the prosoma, the small one located in the middle and the anterior one larger and rounded. Scutum rectangular, type iota (i) with the lateral clear areas well marked. Chelicera with heterogeneous dentition, movable finger with a basal triangular tooth. Penis with the pars distalis spear-shaped, with two short pairs of MS C and two pairs of MS A, both contiguous and forming a lateral row.

AbbreviAtions
remArKs Cruz-López & Francke (2015) recovered Karos Goodnight & Goodnight, 1944 genera-group clade (currently Karosinae) with nine synapomorphies: mesotergal areas not completely covered with tubercles, ocularium in the middle of prosoma, ocularium small, cheliceral dentition homogeneous, no sexual dimorphism on chelicera size, males with chelicera small, follis of penis not on apical depression, pedipalpal femur with a mesodistal setiferous tubercle and pedipalpal patella with mesal armature. At that moment, Cruz-López & Francke (2015) considered that the anterior rounded lobe on prosoma of Mictlana inops was the ocularium due to the size of the structure, being in this way a reversion from the synapomorphy "ocularium in the middle" to the anterior position on prosoma in this species. Later, Cruz-López & Francke (2017) postulated the possibility that the small lobe on the middle of the prosoma could be the ocularium by comparison of this structure with the true ocularium of other karosins, and then, the anterior lobe would be a developed frontal bulge, structure widely found in other karosins but poorly studied; without evidence of eyes position, this supposition is uncertain. Clear figures of the frontal bulge are available in the description of Karos morronei Cruz-López, 2018 (Cruz-López 2018a: figs 5-7). Similar problem determining the position of the true ocularium was detected by Cruz-López et al. (2016) on the troglobitic Belizean Jarmilana pecki (Goodnight & Goodnight, 1977), a pyramidopid harvestman without eyes or retina evidence, and with two dorsal lobes on prosoma.
The character "Chelicera with homogenous dentition", another synapomorphy of Karosinae, was recovered as a reversion to the plesiomorphic state, heterogeneous dentition, in M. inops in Cruz-López & Francke (2015). In a broader phylogeny of Stygnopsidae, cheliceral dentition is a homoplastic character through the family, causing conflict to a  (2017), Mictlana was recovered as monophyletic with high support (posterior probability 0.91), including a putative female and uncertain immatures of H. planus. Now with the inclusion of H. planus in Mictlana, the presence of a large rounded anterior lobe on prosoma could be considered a putative synapomorphy of this genus, regardless whether or not it is the ocularium or the anterior bulge. (Goodnight & Goodnight, 1973) n. comb.  remArKs During the revision of stygnopsid types deposited at the AMNH, penises of some of them were found lost. Even though the penis of Hoplobunus planus is quite damaged, penial morphology was clear, with two pairs of short MS C and A on lateral margins, remarkably similar to those on M. inops. Also, both lobes on prosoma are present, but in M. plana n. comb the middle one is barely noticeable.

Body (Figs 1; 2)
Scutum type zeta (ζ) with constriction 1 shallow, constriction 2 not marked, posterior margin wider than mid-bulge area. Ocularium at the frontal margin of scutum, base cylindrical, apically rounded, with no eyes. With lateral clear areas teardrop-shaped, at level of mesotergal area II. Dorsum smooth, with few and very small tubercles in the middle of each mesotergal areas. Sulcus I well marked, sulci II-IV shallow. Free tergites without ornamentation. Coxae I-IV simi-lar in size ventrally, ornated with long spiniform setiferous tubercles, larger on coxae I and II. Stigmatic area triangular, spiracles hidden between coxae IV and stigmatic area. Free sternites without ornamentation.
Chelicera (Fig. 3A, B) Basichelicerite elongated, with bulla well marked and ornated with spiniform tubercles dorsally and ventrally. Cheliceral hand swollen, covered with many setae. Fixed cheliceral finger with five teeth, the second bifid. Movable finger with four teeth, the basalmost blunt and larger than the others.

Body (Figs 5; 6)
Scutum type zeta (ζ) with the mid-bulge not marked, lateral margins straight, posterior margin of scutum wider than midbulge section giving the appearance of trapeze; ocularium at the frontal margin, wide and rounded, no eyes. Lateral clear areas teardrop-shaped, at level of mesotergal area II. Sulcus I very deep, sulci II-IV shallow. Coxae I and II with similar size, coxae III and IV similar in size and slightly larger than coxae I and II. Coxae I and II ventrally ornated with a row Table 2. -Pedipalpal and leg measurements in mm of the holotypes of Brujita chapulapa n. gen., n. sp. and Toojah cimutaa n. gen., n. sp. Abbreviations: Tr, trochanter; F, femur; P, patella; T, tibia; M, metatarsus; T, tarsus; LI-IV, legs I to IV.

Species Appendage Tr F P T M T
Brujita chapulapa n. gen., n. sp. of long spiniform setiferous tubercles; coxae III and IV with a row of widely spaced tubercles. Stigmatic area reverse "T" shaped, spiracles not hidden.
Chelicera (Fig. 7A, B) Basichelicerite with long bulla, covering almost all segment. Cheliceral hand swollen, fixed finger with seven teeth, the first and the sixth larger, movable finger five teeth, the basalmost larger and blunt.
Pedipalp (Fig. 7C, D) Trochanter with two large spiniform setiferous tubercles on ventral side, the distalmost larger; femur slightly compressed laterally, with a ventral row of seven spiniform setiferous tubercles, the first three larger and decreasing in size slightly; patella unarmed; tibia with IIi (1 = 2 > 3) and iiIi (3 > 1 = 2 = 4), major SST on mesal and ectal sides indicated on the figure, tarsus with II (1 > 2) on both sides, first setiferous tubercle on mesal margin very large, almost the same length than tarsus. Tarsal claw of the same size that tarsus.
Legs (Table 2) Trochanter III rounded, longer than other trochanters. All segments without armature, except apical portion of femur IV with two ventral rows of reduced tubercles. Tarsal  allocated into Stygnopsinae. Because of this, diagnostic characters of both subfamilies are mainly homoplastic, such as the heterogeneous cheliceral dentition mentioned below, and the uncertain position of the ocularium exhibit by Mictlana.
Regarding putative synapomorphies of both subfamilies, Cruz-López & Francke (2017, 2020 have remarked that despite the complex morphology of Mexotroglinus, "straight mesotergal sulci" is the only character common in all members of Stygnopsinae, while "sinuous mesotergal sulci" is present in all Karosinae. However, this character is somewhat difficult to see, especially on the small species and on those troglobitic species with shallow mesotergal sulci, because it is necessary to use tools such as the scanning electron microscopy to see details of microsculpture of mesotergum (Cruz-López & Francke 2019a, b). In the same way, the presence of cheliceral comb could be another putative synapomorphy of Karosinae (Cruz-López & Francke 2019a), however, SEM is necessary to observe this structure in small species.
As mentioned above, Brujita n. gen. has sinuous mesotergal sulci and cheliceral comb, but unfortunately, these characters could not be illustrated using SEM photos in this work because there are only two specimens of this species. On the other hand, the uncertain identity of the lobe on prosoma that could be interpreted as either the ocularium or the frontal bulge, and also, the heterogeneous dentition, make this new genus another aberrant taxon with a mix of morphological traits of both subfamilies, such as Mexotroglinus and Mictlana. Further morphological characters to reaffirm subfamilial assignment of Brujita n. gen. into Karosinae are: pedipalpal femur and patella with mesal armature, pars distalis of penis compressed, with the flimsy lamina thin, MS A, B and C together forming a lateral row, and follis many times longer than wide.
The subfamilial assignment of Toojah n. gen. is less complex. This genus is easily assigned to Stygnopsinae based on the combination of the following features: mesotergal sulci straight, a frontal lobe on prosoma (probably the ocularium), chelicera wide (probably sexually dimorphic) with heterogeneous dentition, absence of mesal armature on pedipalpal femur and patella, pars distalis not compressed, with the flimsy lamina wide and macrosetal groups A, B, C and E separated from each other. Additionally, MS D on Stygnopsinae generally are one pair of small setae, sometimes two pairs. With the addition of Toojah n. gen. to the subfamily, there are two genera without MS D, i.e. Toojah n. gen. and Iztlina Cruz-López & Francke, 2017.
Cruz-López & Francke (2019b) discussed on the broad assortment of epigean, troglophilic and troglobitic representatives of Stygnopsidae, as this family is one among related families of Gonyleptoidea which has conquered both epigean and hypoean habitats. Also, the previous perception of the troglobitic nature of the family considered by Mendes & Kury (2007) has changed with the discovery of many epigean representatives during the last years (Cruz-López & Francke 2019b). In this way, it is remarkable that nine genera of this family are monotypic; among these nine, six are troglobitic, and among these six, only four are completely blind: Brujita n. gen., Mexotroglinus, Toojah n. gen. and Troglostygnopsis. Also, these genera show morphological traits that complicate their subfamilial allocation, as mentioned above. Their peculiar morphological characters (autapomorphies) have been probably acquired during the caves colonization. housing of L. Prendini and P. Colmenares (AMNH) during a fellowship research at the Museum. Thanks in advance to B. Mendoza (LaNaBio) for her assistance on Electronic Microscope. Many thanks to my friends and colleagues Rodrigo