A new epigean harvestman of the genus Guerrobunus (Laniatores: Phalangodidae), from Hidalgo, Mexico, with taxonomic notes about the genus.

The fifth species of the genus Guerrobunus, Guerrobunus barralesi sp. nov. is described from specimens collected in Hidalgo, Mexico. This species represents the first eastern record from the country and unlike other species of the genus, is completely epigean. Guerrobunus barralesi sp. nov. is compared with the most similar species, Guerrobunus minutus, which also has well developed and pigmented eyes. Finally, external morphology, including male genitalia, taxonomy of the genus, and familial assignment into the family Phalangodidae are discussed.

Two new species of the genus Paramitraceras Pickard-Cambridge, 1905 (Opiliones: Laniatores: Stygnopsidae) from Chiapas, Mexico.

Parainitraceras pickardcanibridgei sp. nov. and Paramitraceras tzotzil sp. nov. from Chiapas, Mexico are described based on specimens previously determined as Paramitraceras granulatum Pickard-Cambridge, 1905 by Goodnight and Goodnight. The male genitalia of the new species and P. granulatum are illustrated with scanning electronic micrographs (SEMs) or drawings derived from them. The importance of the ocular tubercle, cheliceral dentition and sexual dimorphism, pedipalpal armature and male genitalia as taxonomic characters within the genus is discussed as well as differences and similarities between Paramitraceras Pickard-Cambridge, 1905 and its most similar genus, Sbordonia Silhavý, 1977.

Two new genera of epigean harvestmen (Opiliones, Stygnopsidae) from Oaxaca, Mexico, with an identification key for the stygnopsine genera.

Two new genera, Ampliphallus gen. nov. and Guelaguetzia gen. nov., are described from material collected in the state of Oaxaca, Mexico. The genus Ampliphallus gen. nov. is monotypic and contains the species A. chimalapaensis sp. nov., from the tropical rain forest of Santa María Chimalapa, Oaxaca. The genus Guelaguetzia gen. nov. is composed of two species: G. cuicateca sp. nov. (type species) and G. serrana sp. nov., from pine forests in northern Oaxaca. These genera can be recognized from each other mainly by the armature of leg IV and by the male genitalia; both are also compared with the remaining members of the Stygnopsinae. An identification key for all genera of the subfamily is provided.

A new leaf-litter harvestman species of the genus Karos (Opiliones: Stygnopsidae: Karosinae), with a reanalysis of the morphological phylogeny of the genus.

Karos Goodnight Goodnight, 1944 is the most diverse genus of the family Stygnopsidae. It contains seven micro-endemic species from the Huasteca region in eastern Mexico. In this paper, the new species Karos morronei sp. nov. is described based on the morphology of adults of both sexes. The new species is from Zacualtipán de Ángeles, Hidalgo State, which represents the southernmost record for the genus. Additionally, a reanalysis of the previous morphological phylogeny of the genus using both parsimony and maximum likelihood methods is provided. According to the morphological reanalysis, K. morronei sp. nov. exhibits an autapomorphy (males with femur IV thicker than females) and is the sister group of the clade that includes K. barbarikos, K. hexasetosus, K. monjarazi, K. parvus and K. singularis. Finally, information of barcoding (CO1) is provided for this new species.

A second species of the genus Martensolasma (Opiliones, Dyspnoi, Nemastomatidae) from Mexico.

A second species of the previously monotypic genus Martensolasma Shear, 2006 is described: Martensolasma catrina sp. n., based on specimens collected in Metztitlán, Hidalgo, Mexico. The taxonomy the genus is briefly discussed.