Morphology-based cladistics splinters the century-old dichotomy of the pied harvestmen (Arachnida: Gonyleptoidea: Cosmetidae)

Abstract

The cosmetids are conspicuous harvestmen, remarkably diverse in size, shape and colour. However, the effectiveness of all these morphological traits for diagnosing groups is scarcely explored in the literature. Since the early 20th century, the family Cosmetidae has been divided into two subfamilies, Cosmetinae and Discosomaticinae, and there has been no further effort to delimit additional or alternative subfamilial groups. In this analysis, we aim to test the issue of the basal dichotomy of Cosmetinae and Discosomaticinae. Thus, we propose a more comprehensive phylogenetic analysis using both parsimony and Bayesian approach, comprising 103 terminals of Cosmetidae, plus seven outgroup terminals scored for 130 morphological characters. Discosomaticinae is revisited and all its species were included in our matrix. To offer a real challenge to the monophyly of Discosomaticinae, members of 36 genera of Cosmetinae have also been scored. Our results support neither Cosmetinae nor Discosomaticinae sensu Pickard-Cambridge/Roewer as monophyletic groups. We found that Cosmetidae may be organized into a few major clades, which are here diagnosed. Accordingly, taxonomic changes in the arrangement of the family are introduced: description of one new tribe, five new subfamilies and revalidation of a sixth, description of three new genera, and proposition of synonymies, transfers and revalidations at generic level.

A Family Affair: Diagnosing and Delimiting Prostygnidae (Opiliones: Gonyleptoidea)

“…A recent molecular study using UCEs confirms its position inside the clade that includes Metasarcidae and Cosmetidae (MECO) [14] (figure 2), as was initially suggested by Villarreal and García [9] and supported in the topology of the phylogenetic trees obtained by Kury [6] (figure 6), Villarreal [10] (figure 1), Medrano et al [13] (figure 7).…”

“…They alluded to the impending cranaid paper while taking this step. Medrano et al [13] concurred with the placement of Prostygnidae in MECO as the possible sister-group of Cosmetidae.…”

“…However, the internal relationships within MECO are still uncertain. The more recent morphological analysis by Medrano et al [13] proposed Prostygnidae as the sister group of Cosmetidae, with Metasarcidae outside, whereas the molecular analysis proposed by Derkarabetian et al [14] inverted this relation, with Prostygnidae being the sister-group of Cosmetidae + Metasarcidae.…”

Mapping the distribution of armored harvestmen (Opiliones, Laniatores) in Colombia: updated list of species, taxonomic contributions, and insight of diversity in protected areas

“…The type locality for this species is the state of Bahia, in Brazil. It was recorded for Colombia by Medrano et al (2021a) .…”

Systematic revision and total evidence phylogenetic analysis of the Andean family Metasarcidae Kury, 1994 (Opiliones: Laniatores), with description of two new genera and twenty new species

“…The finger-like sac projection is similar to the bump-like sac of cosmetid genus Metalibitia (see Coronato-Ribeiro and Pinto-da-Rocha 2017), but it can be differentiated because the structure in Metalibitia is a folded projection occupying the base to the median region of the lateral part of the VP, whereas in Metasarcidae it is spiny-like and is restricted to the base. Besides that, is a derived genus within cosmetid family (Medrano et al 2021). Considering that they are unique structures among harvestmen, as well as the differences pointed out, we chose to consider them as independent structures.…”