Systematics of the genusMayazomus(Arachnida: Schizomida): the relevance of using continuous characters and pedipalp setae patterns to schizomid phylogenetics

First description of the male genitalia in a short-tailed whipscorpion (Arachnida: Schizomida), description of the female, and comments on pygidial glands and cuticular ultrastructure of Surazomus algodoal Ruiz & Valente, 2017

The male genitalia of Surazomus algodoal Ruiz & Valente, 2017 are described. Since this is the first attempt to describe male genitalia in the schizomids, we propose new terminology to describe the sclerites of the male genital chamber in the order. We believe that the male genitalia may provide a large set of characters for taxonomic research in schizomids, as the female genitalia have proven to do. The setae and other cuticular structures were investigated using light and scanning electron microscopy (SEM). The female of S. algodoal is described for the first time, including the genitalia, and we highlight the sexual dimorphism present in the species. We also present descriptions of: 1) microtrichia, with respect to their presence/length/distribution, 2) cuticular sensilla, glandular openings and other cuticular structures, proposing new terminology, 3) setae of the pedipalpal trochanter and tarsus. Some changes on the terminology of setae of pedipalpal tibia are also given. These advances may be useful for description in other schizomids. The pygidial glands, mostly ignored in modern papers, were assessed and commented upon.

Patterns in schizomid flagellum shape from elliptical Fourier analysis

The arachnid order Schizomida is a relatively understudied group of soil-dwelling predators found on all continents except Antarctica. While efforts to understand their biology are growing, there is still much to know about them. A curious aspect of their morphology is the male flagellum, a sexually dimorphic, tail-like structure which differs in shape across the order and functions in their courtship rituals. The flagellar shape is important for taxonomic classification, yet few efforts have been made to examine shape diversity across the group. Using elliptical Fourier analysis, a type of geometric morphometrics based on shape outline, we quantified shape differences across a combined nearly 550 outlines in the dorsal and lateral views, categorizing them based on genus, family, biogeographic realm, and habitat, with special emphasis on Caribbean and Cuban fauna. We tested for allometric relationships, differences in disparity based on locations and sizes in morphospace among these categories, and for clusters of shapes in morphospace. We found multiple differences in all categories despite apparent overlaps in morphospace, evolutionary allometry, and evidence for discrete clusters in some flagellum shapes. This study can serve as a foundation for further study on the evolution, diversification, and taxonomic utility of the male flagellum.

Integrative systematics untangles the evolutionary history of Stenochrus (Schizomida: Hubbardiidae), a neglected junkyard genus of North American short-tailed whipscorpions

Until recently, the Nearctic short-tailed whipscorpion genus, StenochrusChamberlin, 1922, included 27 species distributed primarily in Mexico, the USA and Central America. Morphological disparity among its species, associated with their adaptation to diverse habitats, raised the question as to whether Stenochrus was monophyletic. The phylogenetic relationships among short-tailed whipscorpions have only recently begun to be explored, and the monophyly of Stenochrus had never been tested. The present contribution provides the first phylogeny of Stenochrus and related genera, based on 61 morphological characters and 2991 aligned DNA nucleotides from two nuclear and two mitochondrial gene markers, for 73 terminal taxa. Separate and simultaneous analyses of the morphological and molecular data sets were conducted with Bayesian Inference, Maximum Likelihood, and parsimony with equal and implied weighting. Terminals represented only by morphological data (‘orphans’) were included in some analyses for evaluation of their phylogenetic positions. As previously defined, Stenochrus sensuReddell & Cokendolpher (1991, 1995) was consistently polyphyletic and comprised eight monophyletic clades, justifying its reclassification into eight genera including Heteroschizomus Rowland, 1973, revalidated from synonymy with Stenochrus by Monjaraz-Ruedas et al. (2019). Rowland & Reddell’s (1980)mexicanus and pecki species groups were consistently paraphyletic. Orphans grouped with the most morphologically similar taxa.

Description of a new species of Surazomus (Arachnida: Schizomida), with comments on homology of male flagellum and mating march anchorage in the genus

Surazomus saturninoae sp. nov. is described from eastern Amazon. The male has a pentagonal flagellum, similar to those of three other species in the genus. These four species are herein gathered as the arboreus-group of Surazomus. We present a brief synopsis of chaetotaxy description in hubbardiines and several homology proposals for the flagellum of the species in the arboreus-group: the posterior lobes may be homologous to the lateral lobes of hubbardiine species with trilobed flagella; the setal brush with 4-5 setae on the posterior lobe may be composed of one Dl2 seta and enlarged lobular microsetae; the single, median posterior coupling pocket may be homologous to the pair of posterior pockets seen in other hubbardiines; the single, median anterior coupling pocket may be homologous to the pair of pockets on the anterior border of the flagellum seen in other hubbardiines. Based on the morphology of these pockets and the chelicerae within Surazomus, we discuss the anchoring mechanism during the mating march.