Ephippiochthonius Beier 1930
Creators: name: Zaragoza, Juan A.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Pseudoscorpiones
Chthoniidae
Ephippiochthonius

description: Genus Ephippiochthonius Beier, 1930 n. stat.
Diagnosis. Genus of the tribe Chthoniini with ephippiochthonian chela, chelal hand usually weakly depressed at level of trichobothria ib / isb, distad of these trichobothria with a large, more or less prominent hump, followed by a continuous depression towards base of fixed finger, giving the dorsal contour a more or less marked step-like appearance in lateral view (Fig. 1); without a ventral hollow before base of movable finger; base of chelal hand not abruptly constricted paraxially; prominent bow-like medial protuberance (ip) present between chelal condyles, slightly closer to the paraxial one; distal end of hand and bases of chelal fingers with strongly sclerotized condylar complex; proximal portion of chelal hand with only 3 setae in adults and tritonymphs, seta ph3 lacking, usual chaetotaxy: 4:5:3 (Figs 1–3). Movable pedipalpal finger slightly shorter than the fixed; axis of fixed finger apically forming a slightly obtuse angle; both fingers mostly straight; dental rows homo- or heterodentate, bearing spaced, upright teeth, without saw-like dentition, third tooth of normal row (mt) of fixed finger not modified; tip of fixed finger with an accessory tooth (td) on antiaxial face; tip of fixed chelal finger of male, tritonymph and deutonymph with a deep hollow on paraxial face and a subapical protuberance (sp), latter lacking in female; coupled sensilla pc usually between trichobothria sb and b, rarely level with sb or, exceptionally, distad of sb; base of movable chelal finger with an enlarged sclerotized condyle (bc), followed by a long, well sclerotized apodeme. Lyrifissure ma1 always present, ma2 present or absent, depending of the species-groups concerned. Anterior margin of carapace more strongly dentate between median macrosetae, straight or weakly prominent, without a well-defined epistome. Coxae II and III with coxal spines; bisetose intercoxal tubercle present between coxae III and IV; distal marginal seta of pedipalpal coxal disk usually distinctly longer than distal marginal seta of coxa I, exceptionally of same length; Sternite III in males and females usually with 10 marginal setae (not counting stigmatal setae or setae bordering notch in male), of which the lateral one on each side is usually reduced to the size of a microseta (Fig. 5). Male genitalia without median hiatus between guard-setae. Comparison with related genera as in the key and Table 1.
Type species. Scorpio tetrachelatus Preyssler, 1790.
Distribution. Mediterranean-Macaronesian region, reaching eastwards to Iran, and northwards to Scandinavia; two species outside that range are probably introduced: E. virginicus Chamberlin, 1929 (U.S.A.) and E. tetrachelatus (from Eastern Canada, U.S.A. (including Hawaii), Cuba, Argentina, Seychelles and southwestern Australia (Harvey 2013).
Remarks. Ephippiochthonius, in its former broad sense, represented a complex of species groups showing important differences, as in the generic key, Table I and discussed below, giving support to the creation of two new genera: Cantabrochthonius n. gen. and Occidenchthonius n. gen.
Within Ephippiochthonius n. stat., as restricted here, three species-groups are recognized: the fuscimanus, tetrachelatus and gibbus groups, the latter being proposed here. Differences between the tetrachelatus -group and the fuscimanus -group have been discussed in detail by Gardini (2013), to which the following characteristics can be added: presence in the tetrachelatus -group of ma1, ma2 and all the other standard lyrifissures, versus constant absence of ma2 and frequent absence of fd3 and hd in the fuscimanus -group; in the tetrachelatus -group the dorsalantiaxial surface of the chelal hand between the hump and trichobothria eb/esb tends to be flattened, limited by a marked edge (eh) in lateral view (Fig. 1) before recovering the normal curvature on the antiaxial face, whereas this is weakly developed or absent in the fuscimanus -group; the shape of the pointed teeth of the distal half of the movable chelal finger, which are usually wider than long in fuscimanus -group, in contrast to those of the tetrachelatus -group; basal half of movable chelal finger with at least vestigial teeth on a thin lamina in the tetrachelatus -group, but usually with a straight and thick lamina in the fuscimanus -group; trichobothria ib and isb distally united by a chitinized dorsal band in fuscimanus -group, which is absent or weakly developed in the tetrachelatus -group; the distance from esb to ib / isb approximately the same as that between ib / isb and the base of the hand in the tetrachelatus -group, as opposed to distinctly longer in the fuscimanus -group; setae ih1, ih3 and ih4 approximately in a straight row and level with trichobothria ib / isb in the tetrachelatus -group, versus setae ih3 and ih4 well distad of ih1 and ib / isb, sometimes giving the appearance of being part of the distal setae group in the fuscimanus -group. Gardini (2013) noted that the species C. parmensis, C. cassolai, C. berninii and C. thaleri differed from other members of the fuscimanus -group in having a thick marginal lamina, with undulating, partially fused vestigial teeth, on the movable chelal finger, but this discrepancy is eliminated here by their transfer to Occidenchthonius n. gen.
A new group, named the gibbus -group, is proposed here for E. gibbus (Beier, 1953) and related species. These share the following characteristics: fixed chelal finger with 20 or more pointed teeth with dental canals reaching to the base; distal half of movable chelal finger with pointed teeth, longer than wide, proximal half with a thin marginal lamina, mostly weakly undulated with vestigial teeth lacking dental canals; all the chelal lyrifissure groups present in most of their standard numbers, except ma2 and rarely fd3; trichobothria ib / isb equidistant between esb and base of hand; dorsal-antiaxial surface of chelal hand between the hump and trichobothria eb/esb tending to be flattened, limited by a more or less marked edge; setae ih1, ih3 and ih4 approximately in a straight row and level with ib / isb. The gibbus -group seems, in general, closer to the tetrachelatus -group than to the fuscimanus - group, but it differs from the former by the absence of lyrifissure ma2 and the presence of a thin marginal lamina in the basal half. The gibbus -group shares with the fuscimanus -group the absence of lyrifissure ma2, but differs by the presence of lyrifissure hd and by the higher number of teeth on the fixed chelal finger (20 or more, as opposed to mostly less than 15, rarely about 20, in the fuscimanus -group), by the shape of the teeth of the distal half of the movable chelal hand (usually wider than long in the fuscimanus -group) and by the different thickness and shape of the basal lamina, not so marked in the gibbus -group as in fuscimanus -group, and by the position of the chelal hand setae ih1, ih3. The gibbus -group is an informal and possibly non-monophyletic group, mainly distinguished from the tetrachelatus -group by the absence of lyrifissure ma2, which is a neotenic trait. In fact, one specimen each of the species E. amatei (Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2001), n. comb. and E. catalonicus (Beier, 1939), n. comb., within the gibbus -group, has been observed to have lyrifissure ma2 present on one chela and absent on the other. In contrast, the fuscimanus -group is a highly consistent group and may deserve to be recognized as a subgenus within Ephippiochthonius, due to its unique characteristics.
Chthonius virginicus Chamberlin, 1929 is here confirmed to belong to the genus Ephippiochthonius, based on the chaetotaxy of the proximal portion of chelal hand (3 setae, lacking ph3) and presence of a medial protuberance (ip) between the condyles of the chelal hand.
description: Published as part of Zaragoza, Juan A., 2017, Revision of the Ephippiochthonius complex in the Iberian Peninsula, Balearic Islands and Macaronesia, with proposed changes to the status of the Chthonius subgenera (Pseudoscorpiones, Chthoniidae), pp. 1-221 in Zootaxa 4246 (1) on pages 32-34, DOI: 10.5281/zenodo.437611