Abstract
A group of Amazonian harvestmen is recognized and described as Amazochroma gen. nov. This taxon includes Discocyrtus carvalhoi Mello-Leitão, 1941 (type species), the only species of Discocyrtus previously thought to occur in Amazonia, and Amazochroma pedroi gen. et sp. nov., described here from the Brazilian states of Acre and Rondônia. New records are added for Amazochroma carvalhoi gen. et comb. nov, expanding its distribution from the Brazilian state of Mato Grosso northwards also to Pará and Amazonas in Brazil and additionally French Guiana and Suriname. Diagnostic features of Amazochroma gen. nov. include: trichromatic pattern of legs, dry marks on the dorsal scutum and base of legs and diastema in the row of macrosetae C of the penis ventral plate. A morphological maximum parsimony analysis (1022 scorings; 16 taxa; 64 characters) is performed to test whether Amazochroma gen. nov. is a member of Discocyrtus and if the traditional allocation of Discocyrtus in Pachylinae is defendable. A clade is retrieved containing three groups: (1) Mitobatinae, (2) Discocyrtus and (3) a clade containing Amazochroma gen. nov., Discocyrtanus and Roeweria, here described as a new subfamily of Gonyleptidae – Roeweriinae subfam. nov. Discocyrtanus Roewer, 1929 and Roeweria Mello-Leitão, 1923 are accordingly here transferred from Pachylinae to Roeweriinae subfam. nov.
Highlights
Discocyrtus Holmberg, 1878 is one of the most diverse genera of Laniatores harvestmen, counting 67 valid species (Kury 2003, 2008; Kury & Carvalho 2016)
The clade formed by Amazochroma gen. nov., Discocyrtanus and Roeweria is here described as Roeweriinae subfam. nov., which is part of a more inclusive group including the Mitobatinae, Neopachylus Roewer, 1913 and Discocyrtus
This clade is in turn a sister group of Roeweria, forming a clade that we describe below as Roeweriinae subfam. nov
Summary
Discocyrtus Holmberg, 1878 is one of the most diverse genera of Laniatores harvestmen, counting 67 valid species (Kury 2003, 2008; Kury & Carvalho 2016). The current diagnosis of Discocyrtus dates from Soares & Soares (1954: 245), which in turn directly reflects the “Roewerian” classification system (as nicknamed by Henriksen 1932). The use of formulaic meristic characters such as tarsal counts, and armature of scutal areas and free tergites is not capable, alone, of satisfactorily discriminating among the increasing discovered diversity of genera in Gonyleptidae. The vast majority of species of Discocyrtus (58 valid species) has been described in the first half of the 20th century, with the meager addition of two species later in that century (by Soares & Soares 1970 and Tavares 1981). After a long stagnant hiatus, an isolated cavernicolous species was described by Kury (2008)
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