The family Phrynidae has been mainly recorded from America, including the Antilles, and Heterophrynus is one of its genera endemic of South America and is mainly associated with Amazonian ecosystems. Currently, the genus has 16 valid species, but many original descriptions are ambiguous or incomplete. The more complete work about this genus only includes seven of the currently valid species, and in some cases, some characters useful for the species identification, were not described. This situation hampers the species recognition and the comparison among species to propose diagnosis accurate. Using characters from the male and female genitalia to improve the diagnosis, we present complementary descriptions for four species of Heterophrynus and describe two new species. We present details of morphologic variation, compare the pedipalp spines among the species, present actualized distributions, and for first time, we present a complete illustration of the male genital of eight species using SEM pictures.

Se evaluó la variación morfológica de Heterophrynus boterorum con relación a su distribución geográfica, comparando poblaciones de la vertiente oriental y occidental de la cordillera Central y una población de la cordillera Oriental de los Andes, en los departamentos de Tolima y Quindío, Colombia. Mediante técnicas de estadística univariada y multivariada, (ACP, ANOVA y Kruskal-Wallis), se compararon poblaciones presentes en municipios de ambas vertientes y cordilleras. Se encontró variación entre poblaciones en 15 de 33 caracteres morfológicos examinados. La mayor variación se encontró en el tamaño de palpos, número de espinas y tubérculos. La población del municipio de Lérida se diferenció notablemente de las demás poblaciones del análisis. El resto de poblaciones formaron un grupo morfológico con amplia variabilidad, principalmente en tamaño. Heterophrynus boterorum podría considerarse como modelo de estudio para el efecto del gradiente ambiental y altitudinal de los Andes en la diversificación morfológica de los Amblypygi.

Mexico is the country with the largest diversity of the genus Phrynus (Amblypygi: Phrynidae); however, many species could remain hidden due to the conservative morphology of the group. Two of the Mexican species, P. operculatus, and P. jalisco show enough variation, between populations from different localities, to be considered as possible species complexes. The scarce taxonomic information of these species and the few analyses of their variation could cause misidentifications and sub estimation of the diversity. Specimens morphologically similar to P. operculatus from different Mexican localities were analyzed, using characters from the male and female genitals. Four new species are described, presenting illustrations of SEM for the male genitals. Details of the morphologic variation in this group of species are discussed, as well as the usefulness of sexual characters like the size proportions, and sclerotization in the female gonopods, and ornaments in males, to improve the diagnoses of the Mexican Phrynus. The known distribution of P. operculatus is large in comparison with those of the other species, after the result of this research, the possibility that it is a larger species complex is evident, thus, it is necessary to increase the morphologic and genetic population studies in this group.

We present the description of Phrynus calypso sp. nov. from Trinidad and Tobago, and Venezuela This species is very similar to Phrynus pulchripes (Pocock), however after examining Colombian specimens of P. pulchripes (ca. type locality), many differences were found. Characters commonly used in diagnosis of Phrynus species are variable and make identification difficult. Differences in a few structures, like pedipalpal spines, could not be enough to provide a useful diagnosis.  It is necessary to account for variation of similar species in conjunction, and select non overlapping groups of characters. Observations in the variation in both species are presented, pointing out sources of confusion, and suggesting alternative characters to support diagnoses. At the moment, details about variation in many species in Phrynus, like that of P. pulchripes, are poorly known, and for this reason a redescription is provided.

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