Osperalycus tenerphagus, a new genus and species of Nematalycidae (Acari: Endeostigmata), is described from Ohio, USA, using light microscopy and low-temperature scanning electron microscopy. Specimens were extracted from two different loam soils. This genus can be readily distinguished from the other genera of Nematalycidae by the simple setae that line the opisthosoma. The mouthparts are especially distinct in possessing three-segmented palps, an unusual vessel-shaped structure, and rutella that overlap at the midline. The discovery of rutella in this genus and in two other genera indicates that the Nematalycidae can be more confidently assigned to the Endeostigmata (Sarcoptiformes). http://www.zoobank.org/urn:lsid:zoobank.org:pub:A64A6612-B66C-4814-80A9-3856DEBE8C46

Morphological support for a clade comprising two vermiform mite lineages: Eriophyoidea (Acariformes) and Nematalycidae (Acariformes)

Describing a substantial proportion of the world’s species could be made much easier by the 3D digitization of collections, which would facilitate the dissemination of taxonomic information locked up in natural history museums. Three-dimensional imaging captures many characters and allows a lot of versatility in the way that morphological data is displayed and used (Wheeler et al. 2012; Faulwetter et al. 2013). Moreover, the loss and damage of valuable specimens, many of which are very fragile, can be reduced as a result of the use and sharing of 3D model substitutes among researchers. This can also lead to a reduction in the handling and transportation expenses of many specimens.

Over the past century and a half, the taxonomic placement of Eriophyoidea has been in flux. For much of this period, this group has been treated as a subtaxon within Trombidiformes. However, the vast majority of recent phylogenetic analyses, including almost all phylogenomic analyses, place this group outside Trombidiformes. The few studies that still place Eriophyoidea within Trombidiformes are likely to be biased by incomplete taxon/gene sampling, long branch attraction, the omission of RNA secondary structure in sequence alignment, and the inclusion of hypervariable expansion–contraction rRNA regions. Based on the agreement among a number of independent analyses that use a range of different datasets (morphology; multiple genes; mitochondrial/whole genomes), Eriophyoidea are almost certain to be closely related to Nematalycidae, a family of vermiform mites within Endeostigmata, a basal acariform grade. Much of the morphological evidence in support of this relationship was apparent after the discovery of Nematalycidae in the middle of the 20th century. However, this evidence has largely been disregarded until very recently, perhaps because of overconfidence in the placement of Eriophyoidea within Trombidiformes. Here, we briefly review and identify a number of biases, both molecular- and morphology-based, that can lead to erroneous reconstructions of the position of Eriophyoidea in the tree of life.

The cheliceral digits of soil inhabiting Nematalycidae are among the shortest of any chelicerate (≈5 µm long). But Eriophyoidea, which may be nested within Nematalycidae, have relatively long (10–70 µm), styliform cheliceral digits that are enveloped within a subcapitular sheath. Scanning electron microscopy observations on the mouthparts of a nematalycid, Cunliffea cf. strenzkei (Cunliffe), show it has a rudimentary sheath for chelate (“biting”) chelicerae. This discovery – presented herein – is the basis for a new hypothesis, which proposes that the stylet sheath of Eriophyoidea could have originated when the chelicerae were still chelate. Accordingly, the sheath would have originally covered the space between the fixed and movable digits, extending the preoral cavity anteriorly. As the digits became increasingly styliform, the sheath would have expanded around them, otherwise the hermetic seal of the preoral cavity would have been compromised. The sheath would have expanded for this reason until it reached its extant form, which completely envelops the digits.