A new genus of minute Sparianthinae spiders from the Caribbean (Araneae, Sparassidae)

Abstract The monotypic genus Diminutella gen. n. is proposed to include the type species, Diminutella cortina sp. n., described from San Diego de los Baños, based on male and female specimens. This species is amongst the smallest Sparianthinae known to date reaching only 4.4 mm body length. It can be distinguished from other Sparianthinae by the combination of eye arrangement, with anterior eye row recurved, posterior eye row straight, spination pattern of legs I–II, with three ventral pairs on tibiae and one on metatarsi, and by the peculiar genitalia, with male palps bearing a large, laminar, layered conductor that rests within a retrolateral depression in the cymbium, and a female vulva with long copulatory ducts coiled around the stalk of a globose blind ending appendage.

The subfamily occurs worldwide, but the Neotropical region is particularly rich in terms of Sparianthinae fauna and recent papers (Rheims 2013, 2017, Rheims and Alayón 2014, 2016 show that the number of new species and genera is growing as its systematics is studied. Eight genera and 54 species are known from the region: Decaphora (5 species), Defectrix (1 species), Neostasina (27 species), Pseudosparianthis (8 species), Sampaiosia (1 species), Sparianthis (1 species) Stasina (4 species) and Uaiuara (7 species) (World Spider Catalog 2018). The four Neotropical species currently included in Stasina are not congeneric with the type species, Stasina spinosa Simon, 1897, and are considered misplaced in the genus (Rheims and Alayón 2016). Most are only known from juveniles and cannot be placed in any other genera until the adults are collected. The monotypic genus Defectrix is known solely from a juvenile. However, the original description includes traits that are not found in Sparianthinae, such as notched trochanters (smooth in Sparianthinae), only two pairs of ventral spines on tibiae I-II (three or more in Sparianthinae) and absence of a colulus (present in Sparianthinae) (Petrunkevitch 1925). We consider it misplaced in the subfamily and thus, consider that only six genera are known from the Neotropical region.
In this paper, we describe the new genus Diminutella gen. n. to include a species of minute Sparianthinae, Diminutella cortina sp. n., found in San Diego de los Baños, western Cuba. It is one of the smallest species of Sparianthinae known to date, with total body lengths ranging from 3.5 to 4.4 mm. Amongst Neotropical Sparianthinae, similar sizes are only found in the genus Uaiuara, with total lengths ranging from 3.7-10.0 mm (Rheims 2013). Other small, but slightly larger species belong to the Afrotropical genera Stipax Simon, 1898 and Pleorotus Simon, 1898, both monotypic and endemic to the Seychelles Islands (Simon 1898).
In the absence of a cladistic analysis, not much can be said about the relationships between Diminutella gen. n. and the remaining Sparianthinae genera. However, despite being known from a single species, we consider that the genus represents a monophyletic unit. Diminutella gen. n. shows a combination of somatic characters that is not found in any other genera of Neotropical Sparianthinae and both male and female genitalia are markedly different from all other species known to date. The importance of spines, male palp and female epigyne features was previously pointed out by Rheims & Alayón (2016). Also, Sparassidae species are usually conservative and rarely deviate from the generic bauplan. We consider that, if new species of Diminutella gen. n. are discovered in the future they will show the same characters that are currently used to diagnose the genus and will strengthen our hypothesis that this is a separate lineage within Sparianthinae.

Materials and methods
The examined material is deposited in the collections of the Museo Nacional de Historia Natural de Cuba, La Habana, Cuba (MNHNCu, curator: G. Alayon) and National Museum of Natural History, Smithsonian Institution, Washington D.C., USA (NMNH, curator: J.A. Coddington).
Morphological observations and illustrations were made using a Leica MZ165C stereomicroscope with a camera lucida. Measurements were taken with a micrometric ocular and are given in millimeters. Female genitalia were examined in clove oil after dissection. Photos of dorsal habitus, male palps, and female epigyne were taken using a Leica DMC 4500 camera attached to a Leica M205 A stereomicroscope. Extended focal range images were composed with the program Leica Application Suite version 4.8.0. SEM images were taken with a FEI Quanta 250 scanning electron microscope from the Laboratório de Biologia Celular at the Instituto Butantan. Material used for SEM was mounted on metal stubs and sputter coated with gold.
Abbreviations used throughout the text are given bellow.

Somatic morphology
AER anterior eye row ALE anterior lateral eyes ALS anterior lateral spinnerets AME anterior median eyes

Male palp
Format of descriptions follows Rheims (2007). Spine notation follows Petrunkevitch (1925). Leg measurements are listed as: total length (femur, patella, tibia, metatarsus, tarsus); eye diameters as: AME, ALE, PME, PLE; and interdistances as: AME-AME, AME-ALE, PME-PME, PME-PLE, AME-PME, ALE-PLE. Positions of tegular appendages are given according to clock positions, based on the left male palp in ventral view. In schematic illustrations of female vulva the blind ending appendage is marked with "T", the copulatory opening with a circle, and the end of the fertilization duct in direction of the uterus externus with an arrow. Coloration patterns are described based on specimens preserved in 70% ethanol. Only characters that differ from those of the male are mentioned in the female description. Geographical coordinates of the collection locality were obtained from Google Earth.
Etymology. The specific name is a combination of the Brazilian adjective "diminuto" and the suffix "ella" and refers to the minute size of the specimens of the type species of the genus, considered the smallest Sparassidae known to date. Gender is feminine.
Diagnosis. Species of Diminutella gen. n. can be distinguished from all known Neotropical genera by the combination of the following characters: AER recurved and PER straight (Figs 1A-B), chelicerae with three promarginal teeth and two retromarginal denticles ( Fig. 2A) and legs I-II with three ventral pairs of spines on tibiae and one on metatarsi. They are distinguished from Decaphora by the eye arrangement and cheliceral dentition (AER straight, PER procurved, four promarginal teeth and 5-7 retromarginal denticles in Decaphora); from Neostasina by the eye arrangement (AER straight and PER procurved in Neostasina); from Pseudosparianthis, Sampaiosia and Sparianthis by the number of spines on metatarsi I-II (two pairs in these three genera) and by the eye arrangement (AER and PER procurved in Pseudosparianthis and Sampaiosia and AER and PER recurved in Sparianthis); and from Uaiuara by the number of ventral spines on tibiae I-II (7-9 pairs in Uaiuara).
Distribution. Known only from the type locality.