A new genus of Micromygalinae (Araneae, Microstigmatidae) from Brazil, with transfer of Masteriaemboaba Pedroso, Baptista & Bertani, 2015 and description of six new species

Abstract The family Microstigmatidae is composed of two subfamilies, Microstigmatinae and Micromygalinae, seven genera and 16 species. Micromygalinae is monotypic, comprising the species Micromygalediblemma Platnick & Forster, 1982 from Panama. A new genus, Tonton is described as a new member of the Micromygalinae. Masteriaemboaba Pedroso, Baptista & Bertani, 2015, is transferred to the new genus and six new species from Brazil are described and attributed to Tontongen. n.: the type species, T.itabiritosp. n., T.quecasp. n., T.matodentrosp. n. and T.sapalosp. n., all from the state of Minas Gerais; T.ipiausp. n. from the state of Bahia and T.quiteriasp. n. from the state of Maranhão. Among the cavernicolous species, only T.itabiritosp. n. is considered troglobitic by the total absence of eyes.


Introduction
The spiders of the family Microstigmatidae are known to be small in size, with the exception of Xenonemesia platensis, which can reach about 10 mm (Goloboff 1989). They can be found living in the leaf litter of Central and South America, and South Federal de Lavras, Lavras (UFLA, R.L. Ferreira); Universidade Federal de Minas Gerais, Belo Horizonte (UFMG, A.J. Santos). The type material of Tonton emboaba, was deposited by the authors in the MNRJ; due to a fire in the collection it was not possible to examine them, probably all the types were lost, but material of the type locality was examined. All measurements are in millimeters and were obtained by using an ocular lens with a micrometer scale. Total body size was measured without spinnerets and chelicerae. Width and length of carapace, eye tubercle, labium and sternum are the maximum values. Size of leg segments was measured between the joints in lateral view.
Illustrations were made using a stereomicroscope with camera lucida. For illustrating female genitalia, we used dissected organs; soft tissues were digested for 72 hours using Ultrazyme® enzymatic contact lens cleaner diluted in distilled water. Image stacks were obtained with a Leica DM2500. Female spermathecae were photographed in temporary lamina.
Material for SEM was either air-dried or dehydrated using an ethanol series followed by immersion in HDMS. All material for SEM was fixed to stubs with doublefaced adhesive copper tape and sputter-coated with gold. SEM images were taken using a Quanta 250 Scanning Electron Microscopy with an attached SLR digital camera at Institute Butantan. The descriptions follow Platnick and Forster (1982), with nomenclatural modifications in some terminologies. The spination of the legs follows the model proposed by Petrunkevitch (1925).
Geographic coordinates were obtained using Google Earth (Lat/Long -WGS84) and species distribution maps were made using the DIVA-GIS 7.5 program.
Etymology. The generic name is derived from the Indian Krenak word "tón-tón", and means small. The Krenak Indians, also known as Botocudos or Aimorés and inhabited mainly southeastern Brazil, with great occupation in areas of the state of Minas Gerais. The generic name is neuter.
Distribution. Cave and mountainous region of the state of Minas Gerais and states of Bahia (Atlantic forest) and Maranhão (Brazilian cerrado).  Etymology. The specific epithet is a noun taken in apposition and refers to the type locality.
Diagnosis. Males of Tonton itabirito sp. n. resemble the males of the other species in the genus by the piriform bulb, but differ by the absence of eyes (Fig. 3A). Females are similar to T. quiteria sp. n. by the spermathecae with the thickened internal lobe (Fig. 11E), but differ by the uniform apex ( Fig. 4E-F).
Natural history. Tonton itabirito sp. n. is the only anophthalmic troglobite species here described. The specimens were collected mainly in iron caves in the Quadrilátero Ferrífero Iron Region, in deep regions on the cave floor.

Tonton queca
Etymology. The specific name refers to queca, a cake of English origin, brought to Nova Lima at the time of gold exploration. It became part of the traditional cuisine, as a dessert in the Christmas period and today considered a material good of the municipality.
Diagnosis. Specimens of the T. queca sp. n. can be distinguished from other species by the oval bulb and slender embolus with micro-basal projections (Fig. 5B, D). Females resemble T. sapalo sp. n. by having a spermathecae with narrow duct of the internal lobe and rounded apex (Fig. 9H), but differ by the larger base and distinct setae in all internal lobe ducts (Fig. 6D).
Natural history. All specimens were collected in the iron caves in the Quadrilátero Ferrífero Iron Region. The specimens were collected on the floor below blocks in aphotic zones of the caves, and they are troglobite species.

Etymology. The specific epithet is a noun taken in apposition and refers to the type locality.
Diagnosis. Males of Tonton matodentro sp. n. are similar to those of other species in the genus by the piriform bulb, differing by the apex of embolus, which is enlarged and slightly flattened (Fig. 7C-G). Females resemble T. emboaba by the similar internal lobe of the spermathecae, but differ by the elongated external lobe (Fig. 8D).
Natural history. The specimens of Tonton matodentro sp. n. were collected in the caves in the Quadrilátero Ferrífero Iron Region, on the floor. This species is classified as troglobite.
Etymology. The specific name is an arbitrary combination of letters. Diagnosis. Males of Tonton sapalo sp. n. are similar to the other species in the genus with the piriform palp bulb, but differ by a strong basal curvature on the embo- lus and the embolus apex slightly flat and digitiform (Fig. 9C-G). Females resemble T. emboaba by the similar internal lobe of the spermathecae, but differ by the narrow internal lobe of the spermathecae and longer external lobe (Fig. 9H).
Etymology. The specific epithet is a noun taken in apposition and refers to the type locality.
Diagnosis. Males of Tonton quiteria sp. n. resemble those of other species by the piriform palpal bulb, but differ by the embolus basis wide and tapering to the apex (Fig. 11C); they are close to those of T. ipiau sp. n. by the wide basis of embolus (Fig. 10C), differing by the embolus apex truncate with corrugations (Fig. 11D). Females differ from the other species by the spermathecae with short and thickened lobes (Fig. 11E).
Distribution. Known only from the type locality, Santa Quitéria do Maranhão in the state of Maranhão (Fig. 13).

Discussion
The family Microstigmatidae is currently divided into two subfamilies, easily distinguishable after the phylogeny proposed by Platnick and Forster (1982), the Microstigmatinae Roewer and the Micromygalinae Platnick & Forster (Raven and Platnick 1981;Platnick and Raven 1982). The subfamily Micromygalinae is characterized by having six spinnerets, a single row of teeth on the paired tarsal claws, flattened tarsal organ, enlarged abdominal scutum in males, serrula teeth clumped into a series, only two eyes, short, slightly produced previous lobe on the palpal coxae, palpal conductor and the loss of book-lungs (Platnick and Raven 1982). The inclusion here of Tonton gen. n. within the Micromygalinae expands the generic composition and diversity of this subfamily. The new genus is well supported, especially by the presence of four spinnerets (Fig. 2D), serrula teeth clustered into a series of rows (Fig. 1D), presence of book-lungs (Fig. 2C) and absence of the conductor in the male palp (Fig. 3F).
In addition, Micromygale is exclusively distributed within Panama, whereas Tonton gen. n. is distributed throughout the Neotropics, though this may be biased due to the absence of more soil sampling in the north of the Americas. This was pointed out by Platnick and Forster (1982) where they express that the fauna of mygalomophs within the leaf litter is still practically unknown. However, recent data published on Masteriinae (Dipluridae) (Passanha and Brescovit 2018) can serve as a comparison, because these tiny spiders have been confused with species of Tonton gen. n. in Brazil. The Figure 14. Distribution maps. Epigean fauna. A T. sapalo sp. n., green star, T. ipiau sp. n., orange losangue and T. quiteria sp. n., yellow circles. Caverniculous fauna B T. emboaba red star and T. itabirito sp. n., blue pentagon C T. queca sp. n., red square D T. matodentro sp. n., red circles. monotypic genus Micromygale (with the type species M. diblemma) presents a joint distribution with species of Masteria in Panama, sharing the distribution of species of Masteriinae (see Passanha and Brescovit,39,45) with M. downeyi (Chickering, 1966) and M. spinosa (Petrunkevitch, 1925) (Passanha and Brescovit 2018: figs 32, 33). The other species of Masteria and species of other genera of Masteriinae are distributed in the Antilles and Amazon region (Almeida et al. 2018, Passanha andBrescovit 2018). In relation to the species within Tonton gen. n., all current samples show a disjunctive distribution of the Masteriinae (Fig. 13) with confirmed occurrence in the Brazilian states of northeast and southeast, with many species occurring in natural cavities, despite only one of them being considered a troglobite.