On the trapdoor spiders of Mexico: description of the first new species of the spider genus Aptostichus from Mexico and the description of the female of Eucteniza zapatista (Araneae, Mygalomorphae, Euctenizidae)

Abstract A new species of the spider genus Aptostichus Simon, 1891 is described from a cave in Huautla de Jiménez, Oaxaca, Mexico: Aptostichus sabinae sp. n. This species represents the first new species described from Mexico and the southernmost record in North America for the genus so far. Aptostichus sabinae sp. n. represents the forty-first species described for the genus, which has the highest species diversity in the family Euctenizidae. Eucteniza zapatista is redescribed based on five new males and the first known female from the Parque Nacional La Malinche (PNLM), Tlaxcala Mexico. Eucteniza zapatista is the fourth species of the genus where a female is known, and one of fourteen species described for the genus to date.


Introduction
Discovery.V8 stereoscope. A Zeiss Axiocam 506 color camera attached to a Zeiss AXIO Zoom.V16 stereoscope was used to photograph the different structures of specimens. All structures photographed under the stereoscope were submerged in gel alcohol (available commercially as a hand cleaner). The firm consistency of the gel allows for the immobilization and positioning of the structure to be photographed. The structure suspended in the gel alcohol was covered with 80% liquid ethanol to minimize diffraction during examination and photography. All measurements in the descriptions are in millimeters (mm). Photographs were edited with Adobe Photoshop CS6.
The holotype specimen of Aptostichus sabinae sp. n. is deposited with its collection code in the Colección Nacional de Arácnidos (CNAN) of the Instituto de Biología UNAM (IBUNAM), Mexico City. The holotype of Eucteniza zapatista Bond & Godwin, 2013 was previously deposited in the American Museum of Natural History (AMNH), New York, U.S.A. The specimens of E. zapatista used for this work, are deposited with their collections codes in the collection of the Laboratory of Arachnology (LATLAX), Laboratorio Regional de Biodiversidad y Cultivo de Tejidos Vegetales of the Instituto de Biología UNAM (IBUNAM), Tlaxcala City. Morphological nomenclature and measurements follow Bond (2012) and Bond and Godwin (2013).
Abbreviations used in the description are: B bulb; Cl, Cw carapace length and width (widest part); Cy cymbium; E embolus; LBl, LBw labium length and width taken from the longest and widest points, respectively; PTl, PTw male palpal tibia length and width (widest part in dorsal view); STRl, STRw sternum length and width (widest part); v ventral; p prolateral.
Female. Unknown. Remarks. Aptostichus sabinae sp. n. resembles Aptostichus asmodaeus (Bond 2012: figs 127-132), from Contra Costa County, Mount Diablo State Park, California mainly in the shape of the retrolateral-ventral small finger-shaped projection on metatarsi I (arrows Figs 17, 18; Bond 2012: fig. 128). However, the spination pattern in leg I, the embolus and bulb shape (Figs 10, 12), the spination pattern on the ventral and prolateral part of palps tibiae (Fig. 11) (absent in A. asmodaeus; Bond 2012: figs 131, 132), and the opisthosoma dorsal pattern differ in both species (Bond 2012: figs 127-132). Following Bond (2012) and the synapomorphies that support each species groups, Aptostichus sabinae sp. n. does not fit into any of the groups. The sierra species group composed by four species is supported by two synapomorphies: long sternum and a long male metatarsus I (Bond 2012: figs 337, 338, 340), in A. sabinae the sternum is nonagonal shaped (Fig. 4) and the male metatarsus I is shorter (Figs 13, 14). The simus species group composed by eight species and supported by six synapomorphies: 1) absence of cuspules on male endites, present in A. sabinae (Fig. 7); 2) male palpal tibia stout (Bond 2012: figs 278, 287), in A. sabinae the palpal tibia is thinner (Figs 8,9); 3) male palpal tibia spines short and positioned retrolaterally (Bond 2012: figs 278, 287), in A. sabinae the palpal tibia spines are long, scattered and positioned prolaterally (Figs 8,9); 4) stout embolus (Bond 2012: figs 277, 306), A. sabinae has a long and thin embolus (Figs 10, 12); 5) embolus is dorsalventrally compressed (Bond 2012: figs 277), in A. sabinae is not (Figs 8,9,10,12); and 6) retrolateral, distal most aspect of the cymbium formed as a distinct process (Bond 2012: fig. 277), absent in A. sabinae (Fig. 10). The hesperus species group, composed by thirteen species, is supported mainly by an offset retrolaretal rastellar spine (Bond 2012: fig. 189), which is absent in A. sabinae (Fig. 5). Also, four characters support the monophyly of this species group: 1) lighter carapace and 2) abdominal coloration, whereas in A. sabinae both colorations are darker than the other species of the group (Figs 1, 3); and 4) long and 5) sinuous spermathecal stalk, is unknown in A. sabinae. Finally, the atomarius species group, the most diverse and composed by fifteen species, is supported by three weak synapomorphies: 1) heavy carapace pubescence (Bond 2012: figs 101, 113), 2) dense female tarsal scopulae (38) and a distinct secondary spermathecal bulb. However, the carapace of A. sabinae has a slight carapace pubescence (Fig. 3), and the spermathecal bulb is unknown so far. Because to the synapomorphies explained above and mostly of them absent in A. sabinae, its placement within any of the species group proposed by Bond (2012) is uncertain. For that reason, we consider this new species as inserta sedis until the female of the species and more data and mainly new species from Mexico can be collected.
Natural history. The holotype specimen was hand collected inside a cave, in a temperate forest at 1919 m of elevation. Although the specimen was collected in a cave, it does not present any troglomorphism or adaptation to cave life, and so might be considered a trogloxene.
Natural history. All specimens examined were collected in the PNLM, a temperate pine-oyamel forest at 3000-3250 m of elevation (Fig. 52). The four specimens (LATLAX-Ara0031) were collected using pitfall traps in a pine forest (Fig. 52). The specimen (LATLAX-Ara0033) was hand collected walking on the ground. The female (LATLAX-Ara0032) was hand collected from a vertical burrow of ~50-60 cm deep located at 2 m on a wall along road-cut in a pine forest, the female was also found in the bottom of the burrow (Figs 50, 51).

Discussion
In general, to collect trapdoor spiders is a difficult task, and few species have been described using both males and females. Most of them are described using few specimens or even only the male holotypes. The females are more difficult to collect due to their fossorial nature, whereas males, during certain seasons of the year wander, making pitfall traps the best method or technique so far for their collection. As Bond (2012) said: "the most of the species can be collected only during certain times of the year and collecting typically requires that the burrows be excavated, an activity that is often very time-consuming". The best technique so far seems to be that one proposed by Bond (2012), where one must sometimes use a "scraping" technique to find burrows by removing the first few centimeters of topsoil, thereby exposing the silk lined burrow, however, this technique is not very effective in sandy desert habitats (Bond 2012: 6). In the case of the genus Aptostichus, the only way to find females in desert habitats seems to be after winter rains, when the spiders extend, or clean out their burrows, leaving a small mound of sand at the burrow entrance (Bond 2012). Although the genus Aptostichus was expected to have a relatively restricted biogeographic distribution in the southwestern United States and Baja California peninsula in Mexico, where the species are found in different habitats ranging from Mediterranean climates to the arid Mojave and Colorado deserts (Bond 2012: figs 1-6); the genus seems to have a wide spread distribution in Mexico as well. The diversity of the genus in Mexico is unknown, and Aptostichus sabinae sp. n. represents the very first new species described from Mexico. Under sampled biogeographical provinces for this genus such as California and Baja California, Sonora, and the Mexican Montane biotic component and its provinces, as well as the Sierra Madre Occidental, Transmexican Volcanic Belt (TVB), Cuenca del Balsas, and the Sierra Madre del Sur where Aptostichus sabinae was collected, are some of the most biodiverse provinces in Mexico for different groups of mygalomorph (Mendoza 2014, Ortiz andFrancke 2016) and araneomorph spiders (Valdez-Mondragón and Francke 2015).
As the genus Aptostichus, the genus Eucteniza in Mexico has been poorly collected in the Sierra Madre Occidental (Bond and Godwin 2013: fig. 1). Most species have been collected in Mexico, towards the Sierra Madre Oriental, three species in Baja California Sur, and a widespread species in Texas, United States. Eucteniza is currently composed of 14 species, most of which are described from the Sierra Madre Occidental. However, although three species have been recorded in the TVB including Eucteniza zapatista, this biotic province has been poorly collected, mainly towards temperate montane forests mountains of the states of Estado de México, Michoacán, North of Guerrero, Colima and Jalisco, where more collecting remains to be done. The TVB is located in the Mexican Transition Zone, a region of overlap between the Neartic and Neotropic biotic regions, which represents the most biodiverse region in North America (Halffter et al. 1995, Halffter 2003, Brooks 2005, Morrone 2005. The different vegetation types, altitude, and climates of the Mexican biotic components and their biogeographical provinces (Morrone 2004(Morrone , 2005(Morrone , 2014, hints at the possibility that the both genera have even greater diversity than currently described.

Acknowledgments
The first author is grateful to the program "Cátedras-CONACyT", Consejo Nacional de Ciencia y Tecnología (CONACyT), Mexico for the scientific support for the project No. 59: "Laboratorio Regional de Biodiversidad y Cultivo de Tejidos Vegetales (LBCTV) del Instituto de Biología (IBUNAM), Tlaxcala City". We are grateful to Dr. Oscar F. Francke, curator of the Colección Nacional de Arácnidos (CNAN), Instituto de Biología (IBUNAM), for the loan of the specimen to describe Aptostichus sabinae. Thanks to Rebecca L. Godwin for his revision, comments, and suggestions that improved the manuscript. To the students Eduardo Briones Osorno, Alma R. Juárez Sánchez, and Jose Cruz Valerdi Tlachi of the Laboratory of Arachnology (LATLAX), Laboratorio Regional de Biodiversidad y Cultivo de Tejidos Vegetales, IBUNAM-Tlaxcala, Tlaxcala City for their help in the fieldwork. To the herpetologists Victor H. Jiménez Arcos and Anibal Díaz de la Vega for collecting and donation to the collection of the female of Eucteniza zapatista. We are grateful to Victor H. Jimenez Arcos for sharing and allowing the publication of his high quality photographs of the alive female of E. zapatista, many thanks dude! The specimens were collected under Scientific Collector Permit FAUT-0309 from Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT) to Dr. Alejandro Valdez Mondragón (first author); and FAUT-0175 from SEMARNAT to Dr. Oscar F. Francke.