Description and phylogenetic positioning of a new species of Heteropachylus Roewer, 1913 (Opiliones, Gonyleptidae, Heteropachylinae)

Abstract

ABSTRACT Heteropachylus Roewer is the type genus of Heteropachylinae Kury, endemic to the Atlantic forest, Brazil. Heteropachyline males bear free tergites at least partially fused to dorsal scutum, besides other sexually dimorphic features common in gonyleptids as a higher ratio of maximum widths of abdominal scute and carapace and stronger armature of legs IV than females. We newly describe Heteropachylus thelydrias sp. nov. from Bahia, Brazil, in which males look like females regarding the shape of dorsal scute and armature of legs IV. Although the presence of polymorphic males is reported to this subfamily with morphs which may have variable sexually dimorphic features, our species appears to lack strongly developed males. Expanding on previous cladistic proposals, we investigated its phylogenetic positioning and found H. thelydrias sp. nov. as sister to a clade containing the remaining species of Heteropachylus (3 MPTs, 316 steps, CI 0.42, RI 0.60). The synapomorphies for Heteropachylus were armature of ocularium, the ectal armature of pedipalp tibia, calcaneus I lighter than astragalus, glans without digitiform dorsal process, and ventral plate with distal border distinctly concave. Although the branch support was low, we refrained from describing a new genus as it would not reflect the phylogenetic information we found. http://www.zoobank.org/urn:lsid:zoobank.org:pub:B707C01F-B905-4637-A6DF-7597B6C8FC13