Mites (Acari) have traditionally been treated as monophyletic, albeit composed of two major lineages: Acariformes and Parasitiformes. Yet recent studies based on morphology, molecular data, or combinations thereof, have increasingly drawn their monophyly into question. Furthermore, the usually basal (molecular) position of one or both mite lineages among the chelicerates is in conflict to their morphology, and to the widely accepted view that mites are close relatives of Ricinulei.

A harvestman (Arachnida: Opiliones) is described from the Early Devonian (Pragian) Rhynie cherts, Aberdeenshire, Scotland. Eophalangium sheari gen. et sp. nov. is the oldest known harvestman. The material includes both males and a female preserving, respectively, a cuticle-lined penis and ovipositor within the opisthosoma. Both these structures are of essentially modern appearance. The Rhynie fossils also show tracheae which are, again, very similar to those of living harvestmen. This is the oldest unequivocal record of arachnid tracheal respiration and indicates that E. sheari was terrestrial. An annulate, setose ovipositor in the female suggests that it can be excluded from the clades Dyspnoi and Laniatores, in which the ovipositor lacks such annulations. However, the penis shows evidence of two muscles, a feature of uncertain polarity seen in modern Troguloidea (Dyspnoi). The presence of median eyes and long legs excludes Cyphophthalmi, and thus, E. sheari is tentatively referred to the suborder Eupnoi. Therefore, this remarkable material is implicitly a crown-group harvestman and is one of the oldest known crown-group chelicerates. It also suggests an extraordinary degree of morphological stasis within the eupnoid line, with the Devonian forms differing little in gross morphology – and perhaps in reproductive behaviour – from their modern counterp

This paper serves two roles. First, it acts as an introduction to Blender, an open-source computer graphics program, which can be of utility to paleontologists. To lessen the software's otherwise steep learning curve, a step-by-step guide to create an idealized reconstruction of a fossil in the form of a three-dimensional model in Blender, or to use the software to render results from ‘virtual paleontology' techniques, is provided as an online supplemental data file. Second, here we demonstrate the use of Blender with a case study on the extinct trigonotarbid arachnids. We report the limb articulations of members of the Devonian genusPalaeocharinuson the basis of exceptionally preserved fossils from the Rhynie Cherts of Scotland. We use these newly reported articulations to create a Blender model, and draw comparisons with the gait of extant arachnids to produce as accurate a representation of the trigonotarbid flexing its limbs and walking as possible, presented in additional online supplemental data files. Knowledge of the limb articulations of trigonotarbid arachnids also allows us to discuss their functional morphology: trigonotarbids' limbs and gait were likely comparable to extant cursorial spiders, but lacked some innovations seen in more derived arachnids.