Eviulisoma Silvestri, 1910

Enghoff, Henrik, 2018, A mountain of millipedes VII: The genus Eviulisoma Silvestri, 1910, in the Udzungwa Mountains, Tanzania, and related species from other Eastern Arc Mountains. With notes on Eoseviulisoma Brolemann, 1920, and Suohelisoma Hoffman, 1963 (Diplopoda, Polydesmida, Paradoxosomatidae), European Journal of Taxonomy 445, pp. 1-90 : 7-17

publication ID	https://doi.org/ 10.5852/ejt.2018.445
publication LSID	lsid:zoobank.org:pub:852A3F68-B728-413A-B12E-56F306D56C35
DOI	https://doi.org/10.5281/zenodo.5681574
persistent identifier	https://treatment.plazi.org/id/03A10B47-FFFE-FF96-FDD6-F99BFCC4F972
treatment provided by	Plazi
scientific name	Eviulisoma Silvestri, 1910
status

Treatment

Genus Eviulisoma Silvestri, 1910 View in CoL

Eviulisoma Silvestri, 1910: 463 View in CoL (type species: Iulidesmus cavallii Silvestri, 1907: 3 View in CoL , by original designation).

Eoseviulisoma Brolemann, 1920: 163 View in CoL (as subgenus of Eviulisoma View in CoL , elevated to full genus by Hoffman (1953); type species: Strongylosoma iulinum Attems, 1909: 10 , by original designation).

Strandiellus Attems, 1927: 54 View in CoL (synonymized by Attems (1929); type species: Strandiellus cervicornis Attems, 1927: 54 View in CoL , by original designation).

Himatiopus Verhoeff, 1941: 241 View in CoL (synonymized by Jeekel (1968); type species: Himatiopus iuloideus Verhoeff, 1941: 243 View in CoL , by monotypy).

Included species

See Table 2.

Mauriès (1985) described a subgenus of Eviulisoma , based on a species from Morocco. However, a study by Enghoff & Reboleira (in prep.) shows that Jeekelosoma Mauriès, 1985 , should be upgraded to full generic status, and by this action Eviulisoma will again become an endemic Afrotropical genus.

Diagnosis

A succinct diagnosis of Eviulisoma was provided by Hoffman (1953). Supplemented with information from Hoffman (1964, 1971), Jeekel (2003), Vandenspiegel & Golovatch (2014) and the present study, and with an updated terminology (see below), Eviulisoma may be diagnosed as follows:

A genus of Paradoxosomatidae in which:

- paranota are missing, or at most present as tiny keels on ring 2 only

- there is (usually) a process between the coxae of the fourth male legs

- the sternum of body ring 6 is usually deeply excavated

- the collum bears two transverse rows of thin setae, postcollar body rings bear only one such row

- the gonopod coxa usually has a conspicuous meso-anterior lobe

- the gonopod prefemur is shorter than the acropodite, usually less than half as long

- the acropodite consists of at least three branches which seem to originate directly from the prefemur:

- the flagelliform solenomere

- a mesal acropodital process which is often the longest of the acropodital branches

- sometimes an intermediate acropodital process originating between the mesal acropodital process and the solenomere

- a lateral solenophore which serves as protection of the solenomere

Gonopod terminology

Jeekel (2003) gave detailed redescriptions of many species of Eviulisoma , as well as general comments on the gonopods. In Jeekel’s terminology, the gonopod in Eviulisoma consists of a basal coxa, followed by a prefemur and a terminal acropodite. The ʻfemoriteʼ which usually forms a distinct basal ʻshaftʼ of the acropodite is extremely reduced in Eviulisoma , and “Moreover, it has made a torsion of 180° which is shown by the course of the spermal channel along the anterior side towards the lateral side. The result is that the solenomere arises from the lateral side of the femorite” ( Jeekel 2003: 48).

On the acropodite Jeekel (2003) distinguished three elements: the “solenomerite”, the “tibiotarsus” and a mesal process which he called the “postfemoral process”. There has been a long tradition of attempting to homologise parts of millipede gonopods with podomeres of ordinary walking legs, from which the gonopods have evolved. In the colobognathan orders, where the gonopods retain an obviously leglike structure, this is no problem, but in the eugnathan groups (Nematophora, Merocheta and Juliformia) the homologisation is not straightforward. Eugnathan gonopods often show some more or less obvious articulations, sutures, or constrictions which might correspond to articulations between podomeres, but apart from the articulation between coxa and telopodite, these subdivisions of the gonopod probably have nothing to do with the original leg segmentation. Thus, developmental studies on polydesmid millipedes indicated that the entire telopodite corresponds to the prefemur of a walking leg ( Petit 1976). It therefore makes sense to minimize use of a gonopod terminology suggesting homology with walking leg podomeres. VandenSpiegel & Golovatch (2014) already took such a step for Eviulisoma , using the functional term “solenophore” for what Jeekel (2003) called “tibiotarsus”. I suggest a further step in the same direction and herewith propose the terms “mesal acropodital process” and “intermediate acropodital process” for what Jeekel (2003) and Vandenspiegel & Golovatch (2014) referred to as postfemoral processes.

General description of Udzungwan Eviulisoma

In order to minimize redundancy in the species descriptions, the following general description is presented. It is based on the Udzungwan species studied here, but when appropriate, additional literaturebased information from other species is added [in square brackets]. The description applies to adult males.

- 18 podous + 1 apodous body rings + telson, i.e., ʻ20 segmentsʼ. ʻRingʼ is used as short for ʻbody ringʼ in descriptions.

- Body length [13] 14–34 mm; width [1] 1.3–3.4 mm.

- Colour highly variable. Some species are uniform pale whitish (this seems not always to be a result of preservation), some are more or less uniform brownish or even black ( E. biquintum sp. nov., partly), many are more or less strikingly ringed, with metazonites or a part thereof being brown or black, contrasting with pale prozonites (e.g., E. zebra sp. nov., Fig. 1 View Fig. 1 ; E. akkariae sp. nov., Fig. 3 A View Fig. 3 ), one colour form of E. coxale sp. nov. has large brownish dots at the ozopore level, contrasting with a pale background ( Fig. 3B View Fig. 3 ), and one colour form of E. biquintum sp. nov. is pitch black with contrasting white legs ( Fig. 3C View Fig. 3 ).

- Lower part of head capsule ʻclypeo-labral regionʼ with numerous setae up to between antennal sockets; upper part (ʻvertigial regionʼ) with at most a few scattered setae, sometimes arranged in one or more pairs close to midline ( Fig. 4 View Fig. 4 ).

- Antennae ( Fig. 4 View Fig. 4 ) reaching back to ring [2]3–5 when folded along the side of the body. Antennomeres 2–6 of roughly same length, 1 and 7 much shorter.

- Collum ( Fig. 4 View Fig. 4 ) unmodified, with two transverse rows of thin setae, one row near anterior margin, one ca in the middle, laterally somewhat wrinkled.

- Body rings:

- Paranota completely absent or present as inconspicuous, simple ridges on ring 2 only ( Fig. 4 View Fig. 4 ). In some species, such ridges are seen in some specimens, not in others.

- Pleurosternal keels ( Fig. 5 View Fig. 5 ) simple, not prominent, not drawn out as posterior denticles, best developed on rings 2–5(7), decreasing in size backwards, but in some species recognizable as far back as ring 17.

- Surface smooth, sometimes with visible cellular structure, metazonites more or less longitudinally wrinkled, especially ventro-laterally.

- Stricture between pro- and metazonite sometimes smooth, sometimes more or less conspicuously striolate ( Fig. 5 View Fig. 5 ).

- Ozopores opening flush with metazonital surface at ca ⅔ of metazonital length behind stricture ( Fig. 5 View Fig. 5 ).

- A single transverse row of two (1+1) or four (2+2) thin setae often present on metazonites, sometimes only seen on ring 2, sometimes apparently missing (probably abraded in many cases).

- Sterna sometimes with small cones at base of legs ( Fig. 5 View Fig. 5 ), at least on ring 8.

- Telson ( Fig. 5 View Fig. 5 ): - Preanal ring with a long triangular epiproct; lateral setiferous tubercles usually poorly differentiated, sometimes virtually absent; apical tubercles also usually not proment.

- Anal valves (paraprocts) with margin raised as narrow lips.

- Subanal scale (hypoproct) variable, sometimes semicircular, sometimes trapezoid, sometimes with three more or less conspicuous tubercles at distal margin.

- Legs 0.8–1.5 × as long as body diameter. Relative lengths of podomeres variable; femur the longest in

most cases, but in some short-legged species, prefemur is as long as femur, and in a few long-legged

ones, tarsus is as long as or longer than femur.

- Non-gonopodal sexual characters: - Sternum 5 usually with a tongue-shaped /subtriangular / subrectangular process ( Fig. 6 View Fig. 6 ) between anterior legs (pair 4). One species ( E. breviscutum sp. nov.) without a process ( Fig. 36 View Fig. 36 ) and one

( E. biquintum sp. nov.) with a small tubercle between the 4th leg pair and a similar one between the 5th ( Fig. 35 View Fig. 35 ).

- Sternum 6 usually deeply excavated ( Fig. 6 View Fig. 6 ), anterior margin of excavation curved, with a row of long setae. Fig. 6 View Fig. 6 shows a sternum 6 excavation as it appears in most species; deviating morphologies occur in certain species ( Figs 26 View Fig. 26 , 28 View Fig. 28 , 30 View Fig. 30 , 34 View Fig. 34 ). E. breviscutum sp. nov. and E. biquintum sp. nov. have no excavation.

- Scopulae (dense coverings of modified setae) usually present on the ventral side of femur, postfemur,

tibia and tarsus on anterior legs ( Fig. 7 View Fig. 7 ), decreasing in size from anterior to posterior, often disappearing

from (femur and) postfemur on posteriormost legs (scopulae only on tibia and tarsus in some non-

Udzungwan species). E. kangense sp. nov. and E. sternale sp. nov. furthermore with the ventral surfaces

of prefemora and femora flattened and hairless on some leg pairs. No podomeres with swellings or

processes.

- Gonopods ( Fig. 8 View Fig. 8 ):

- Coxa (cx) with a rounded distomedial lobe of variable size.

- Telopodite forming right angles with coxa.

- Prefemoral part (prf) densely hirsute, usually much shorter than acropodite.

- Acropodite consisting of a highly reduced basal part from which solenomere, solenophore, mesal acropodital and sometimes intermediate acropodital process arise at ca same level.

- Solenomere (slm) originating near lateral side of gonopod, simple, whip-like, usually largely concealed within folded solenophore ( Fig. 8 A –B View Fig. 8 ).

- Solenophore (sph) originating on lateral side of gonopod, very variable in shape, sometimes a simple rolled sheet, sometimes with a distinct ʻconductorʼ process guiding the solenomere; in species with an ‘open’ solenophore, an area with parallel ridges (e.g., Figs 12–13 View Fig. 12 View Fig. 13 , 18 View Fig. 18 ) is sometimes seen – whether similar ridges are present in rolled-up solenophores is unknown.

- Mesal acropodital process (map) originating on mesal side of gonopod, mostly but not always the longest part of the acropodite, very variable in shape. In species with an intermediate acropodital process (iap), map is basally closely contiguous with the solenomere and map might be interpreted as a solenomeral process (?parasolenomere). In species without iap, the solenomere articulates with the highly reduced femorite, close to the basis of map.

- Intermediate acropodital process (iap) only present in some species, originating between map and slm, long, slender, often spinose.

Females are generally larger than males. Although females have not been considered in the present species descriptions, it is worth noting that the ventral part of the third body ring (ʻepigyneʼ) and the basal part of the second pair of legs show considerable variation among species ( Brolemann 1920). Also within the Udzungwan species of Eviulisoma , several distinct types of ʻepigyneʼ and second legs exist, but often it was not possible to correlate a particular female morphotype with a particular species as defined by male characters.

Species groups

Four species groups can be recognized among the Eviulisoma species treated here ( Table 3 View Table 3 ). All groups include species with an excavated male sternum 6 and a ventral process /lobe on sternum 5. One group is characterized by the presence of an intermediate acropodital process (iap), one by having the margins of the sternum 6 excavation lobed, one by having a laterally compressed mesal acropodital process (map) and one by having neither of these characteristics, but a large, sheet-like, unrolled solenophore (sph) and, notably, a separate basal part (ʻfemoriteʼ) of the acropodite. Three species are left ungrouped, being not particularly similar to any other new or previously described species. Two of the ungrouped species lack the sternum 6 excavation and the sternum 5 lobe.