Occidenchthonius Zaragoza, 2017, n. gen.
Creators: name: Zaragoza, Juan A.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Pseudoscorpiones
Chthoniidae
Occidenchthonius

description: Genus Occidenchthonius n. gen.
Diagnosis. Genus of the tribe Chthoniini with ephippiochthonian chelal form, more pronounced in the epigean species than in the hypogean representatives, with a more or less marked ventral hollow with thicker cuticle before base of movable finger; base of chelal hand more or less abruptly constricted paraxially; without a medial protuberance (ip) between chelal condyles; proximal portion of chelal hand always with 4 setae in adults and tritonymphs, seta ph3 present, usual chaetotaxy 4:5:4, but paraxial intermediate dorsal seta ih5 is absent in some species (4:4:4) (Figs 10–16). Movable pedipalpal finger slightly shorter than the fixed; axis of fixed finger apically forming a slightly obtuse angle; both fingers mostly straight; dental margin of movable finger more or less undulated in basal half; dental rows homodentate, bearing spaced, upright teeth, one or more teeth in distal half of fixed finger alternating to give saw-like dentition, first two distal teeth always small and pointed, third tooth of normal row (mt) of fixed finger strongly modified in shape and orientation; tip of fixed finger with an accessory tooth (td) on antiaxial face; tip of fixed chelal finger of both sexes and nymphs with a weak hollow on paraxial face, without subdistal protuberance (sp); basal half of movable chelal finger with rounded, partially fused, vestigial teeth, without canals, on raised lamina; coupled sensilla pc usually between trichobothria sb and b; base of movable chelal finger with a distinct enlarged condyle (bc) and proximally with a sclerotized and well developed apodeme. Lyrifissures ma1 and ma2 always absent, hp frequently absent. Anterior margin of carapace more strongly dentate between median macrosetae, usually strongly prominent, rarely produced into a true epistome. Coxae II and III with coxal spines; bisetose intercoxal tubercle present between coxae III and IV; distal marginal seta of pedipalpal coxa disk distinctly longer than that of coxa I, exceptionally of same length; sternite III in male and female usually with 8 marginal macrosetae, rarely 6–9, without lateral short seta on each side. Male genitalia without a median hiatus dividing each row of guard-setae. Comparison with related genera as in the key and Table 1.
Type species. Chthonius (Ephippiochthonius) machadoi Vachon, 1940.
Etymology. A combination of the Latin occidentalis, meaning western, with reference to the main distribution area of the genus, and Chthonius.
Distribution. Mainland Portugal (Coimbra and Faro districts), Canary Islands, mainland Spain (Andalusia, Castilla-La Mancha, Murcia and Valencian Community regions), Sardinia, mainland Italy and neighbouring countries (one species, O. parmensis (Beier, 1963), widespread in Austria, Croatia, Germany, Italy, Slovenia and Switzerland).
Remarks. Mahnert (2011a) proposed the machadoi group within Ephippiochthonius for seven species endemic to the Canary Islands showing “presence of an isolated subdistal tooth on movable cheliceral finger, the presence of a distinct hump on hand dorsum distal to ib / isb and the dentition of the movable chelal finger (a series of acute teeth in distal half, a series of rounded rudiments in basal half on raised basal lamella)”. Although the species C. machadoi Vachon, 1940 (from mainland Portugal) was not expressly mentioned by Mahnert (2011a), it was implicitly included when the name was chosen for the group. A series of species described from mainland Portugal, the Spanish regions of Andalusia and the Valencian Community (Beier 1939; Carabajal et al. 2001a, 2001b, 2011, 2012; Zaragoza 1985a, 1985b, 2012; Zaragoza & Pérez 2013) fit well within this species-group, which now comprises 23 species, most of them hypogean. Gardini (2013), in his revision of Ephippiochthonius from Italy and neighbouring areas, distinguished a subgroup of four species (C. berninii Callaini, 1983, C. cassolai Beier, 1973 C. parmensis and C. thaleri Gardini, 2009) within the fuscimanus -group, characterized by having fused vestigial teeth on a raised lamina on the movable chelal finger. Examination of three of these Italian species during the present study has shown that they all belong to the new genus Occidenchthonius, thus being excluded from the fuscimanus -group.
Many previously known species were assigned to Ephippiochthonius on the basis of the ephippiochthonian shape of the chela, its dentition and the sclerotized condylar complex. When the new characteristics discussed at the beginning of the Systematics section are considered, it becomes clear that the machadoi -group really belongs to a separate genus, here named Occidenchthonius n. gen. The new genus possesses many characteristics that differentiate it from the other known Chthonius -related genera: presence of a marked hollow before base of movable finger, with thicker cuticle; fixed chelal finger with first two distal teeth always small and pointed, third tooth of normal row (mt) usually strongly modified (less so in the Canarian species) and always clearly deviated in orientation, followed by up to 4 teeth that may also be alternatively deviated in a saw-like dentition; basal half of movable chelal finger with rounded, partially fused, vestigial teeth on raised lamina; lyrifissures ma1 and ma2 always absent, which is only otherwise known in Spelyngochthonius among the genera studied; sternite III of males and females usually with 8 marginal macrosetae, without lateral short seta on each side. Also, Occidenchthonius n. gen. differs from Ephippiochthonius s. st. in having 4 setae in the proximal portion of the chelal hand, as opposed to 3 (ph3 absent in Ephippiochthonius), in lacking a medial protuberance (ip) between the chelal condyles, and by the absence in males and nymphs of a subdistal protuberance (sp) over the weak paraxial hollow at the tip of fixed chelal finger, as illustrated by Gardini (2013: figs 24, 176) and Zaragoza (2012: fig. 9).
At least two species-groups can be recognized within Occidenchthonius. The first of these is the machadoi - group, established by Mahnert (2013) for O. machadoi and the Canarian endemic species. This group is characterized by the presence of an isolated subapical tooth (di) on the movable cheliceral finger, chelal hand chaetotaxy 4:4:4 (seta ih5 absent), the presence of cheliceral lyrifissure ldb, and the presence of preocular microsetae. The second is the verai -group, established here for species with the following combination of characteristics: carapace without preocular microsetae, medially prominent, posterior margin with 2 macrosetae; chelal hand chaetotaxy 4:5:4 (seta ih5 present); absence of an isolated subapical tooth (di) on the movable cheliceral finger, and the absence of chelal hand lyrifissure hp. The following species of Occidenchthonius cannot be placed in either of these species-groups for the moment: O. ambrosiae (Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2012), n. comb., O. anae n. sp., O. bullonorum (Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2012), n. comb., O. cardosoi (Zaragoza, 2012), n. comb., O. dubius (Mahnert, 1993), n. comb., O. felgueraorum n. sp., O. minutus (Vachon, 1940), n. comb., O. morenoi (Carabajal Márquez, García Carrillo & Rodríguez Fernández, 2011), n. comb., O. ortunoi n. sp., O. pinai (Zaragoza, 1985), n. comb., O. sendrai (Zaragoza, 1985), n. comb. O. serranoi n. sp. and O. villacarrillo (Zaragoza & Pérez 2013), n. comb. These species differ from those of the machadoi -group by the presence of the chelal seta ih5. They differ from the species of the verai -group in having an isolated subapical tooth on the movable cheliceral finger in most cases, except O. pinai, which differs by the presence of preocular microsetae, and in O. cardosoi, O. ortunoi and O. serranoi, which differ by the presence of lyrifissure hp.
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 126-127, DOI: 10.5281/zenodo.437611