Hylekobolus Wesener, 2009

Wesener, Thomas, Enghoff, Henrik & Sierwald, Petra, 2009, Review of the Spirobolida on Madagascar, with descriptions of twelve new genera, including three genera of ' fire millipedes' (Diplopoda), ZooKeys 19 (19), pp. 1-128 : 97-100

publication ID	https://doi.org/ 10.3897/zookeys.19.221
publication LSID	lsid:zoobank.org:pub:C473F9F6-1AE7-4B3F-B17F-CA1C2709010C
DOI	https://doi.org/10.5281/zenodo.3791471
persistent identifier	https://treatment.plazi.org/id/A90561DE-4844-47EF-8654-19C38A402BA5
taxon LSID	lsid:zoobank.org:act:A90561DE-4844-47EF-8654-19C38A402BA5
treatment provided by	Plazi
scientific name	Hylekobolus Wesener
status	gen. nov.

Treatment

Hylekobolus Wesener View in CoL , gen. n.

urn:lsid:zoobank.org:act:A90561DE-4844-47EF-8654-19C38A402BA5

Type species: Hylekobolus brachiosauroides View in CoL sp. n.

Other species included:

H. rufus View in CoL sp. n.

H. griseus View in CoL sp. n.

H. albicollaris View in CoL sp. n.

H. goodmani View in CoL sp. n.

H. montanus View in CoL sp. n.

H. analavelona View in CoL sp. n.

H. latifrons View in CoL sp. n.

H. andasibensis View in CoL sp. n.

H. marojejy View in CoL sp. n.

H. anjanaharibe View in CoL sp. n.

Diagnosis: legs without coxal processes, but coxa 7 in males always twice as wide as coxa 6 ( Fig. 55B View Figure 55 ), a unique feature for Spirobolellidae . The anterior ( Figs 55L, N View Figure 55 ) and posterior gonopods ( Figs 55M, O View Figure 55 ) of Hylekobolus are unique within the order Spirobolida . Coxite of posterior gonopods basally at mesal margin with a triangular sclerite ( Figs 55O View Figure 55 , 56G View Figure 56 , 57H View Figure 57 , 58G View Figure 58 ), a potential apomorphy of Hylekobolus . Species medium-sized (30 mm) to quite large (75 mm) for species of the Spirobolellidae . Anterior part of body rings usually black, dark grey or reddish, posterior third light brown to white ( Figs 53 View Figure 53 A–C). Telson with a well-rounded preanal process ( Figs 55C View Figure 55 , 56C View Figure 56 ), which is however much shorter than in Granitobolus or Pseudocentrobolus species. Anal valves small, lips absent ( Figs 55C View Figure 55 , 56C View Figure 56 , 57E View Figure 57 , 58C View Figure 58 , 59C View Figure 59 , 60C View Figure 60 ). Collum ventrally not protruding as far as body ring 2, but anteriorly covering first mandibular basal joint as well as part of antenna ( Figs 55A, D View Figure 55 ). Part of head projecting slightly above second mandibular basal joint ( Fig. 55D View Figure 55 ). Such a modified head capsule ( Figs 55D View Figure 55 , 57C View Figure 57 ) and collum ( Fig. 55A View Figure 55 ) are similar to the conditions observed in the South American genus Atlanticobolus ( Hoffman 1979) , as well as the West African genus Amblybolus ( Keeton 1964) , whose family positions are currently unclear ( Hoffman 1980). However, in Hylekobolus only the second mandibular joint and the collum form a shallow cavity for the short antenna ( Fig. 56A View Figure 56 ), while in Amblybolus the area around the ocelli is strongly modified, too ( Keeton 1964; Demange and Mauriès 1975). Similar modifications of the head capsule also appear in numerous species of the family Spirobolellidae , for example in the genus Benoitolus from the Seychelles Islands ( Mauriès 1980). Male legs with tarsal pads only on legs 3–7 ( Fig. 55B View Figure 55 ). Short and wide tarsus with a single pair of long median setae in legs 8 and beyond ( Figs 55H, I View Figure 55 ), unique for Malagasy millipedes. Body ring 7 in males greatly enlarged, ventrally as wide as two regular body rings ( Fig. 57B View Figure 57 ), a character shared only with the Malagasy genus Spiromimus . Anterior gonopods prominently elongated ( Figs 57E View Figure 57 , 58D View Figure 58 ), especially telopodites ( Fig. 55N View Figure 55 ), tips of anterior gonopods well

visible, even in non-dissected specimens ( Figs 55B View Figure 55 , 57B View Figure 57 ). Posterior gonopod coxite and telopodite fused, slender and conspicuously elongated ( Figs 55O View Figure 55 , 56G View Figure 56 ), which is typical for the species of the family. Telopodites arranged face-to-face with one another. Tip of telopodite bent mesally by 60° ( Fig. 34D View Figure 34 ) or (more often) 90° ( Fig. 55O View Figure 55 ).

Distribution and ecology: all species of Hylekobolus were collected in rainforest. Most of the species (6 of 11) were found in Southeastern Madagascar ( Fig. 54 View Figure 54 ). This could represent a collection artefact since a larger amount of inventory work was conducted around Tolagnaro (Fort Dauphin). That only few species of Hylekobolus occur north of Andasibe is puzzling, as it can hardly be accounted for by the lack of more exhaustive inventories. Of special interest is the occurrence of Hylekobolus analavelona sp. n. in the isolated western rainforest of Analavelona. The Analavelona rainforest is isolated by large areas of dry and spiny forest (in which no Hylekobolus species was recorded yet) from other humid forests ( Moat and Smith 2007). Numerous Hylekobolus species are obviously limited in their distribution areas, which have very sharp boundaries ( Fig. 54 View Figure 54 ). The mechanisms explaining those boundaries are as little understood as in other Malagasy millipedes.

Large numbers of Hylekobolus specimens were found inside dead wood. Single specimens walking on the forest floor were rarely discovered. Two Hylekobolus species were often sympatric ( Fig. 54 View Figure 54 ). In such instances, one species was always significantly larger than the other (like H. rufus sp. n. and H. albicollaris sp. n. in Ivorona).

Description. Size of males and females: species-specific, species with 42–51 rings, no apodous ring.

Colour highly species-specific, but posterior margin of body rings always of lighter.

Head: each eye with circa 32–48 ocelli arranged in seven vertical rows ( Figs 55A View Figure 55 , 56A View Figure 56 , 57D View Figure 57 , 58A View Figure 58 ). Labrum with standard three irregular teeth and one row of 10–12 stout marginal setae. Clypeus with two setiferous foveolae on each side ( Figs 57B, D View Figure 57 ). Head around incisura lateralis projecting slightly above basal joints of mandible ( Figs 55D View Figure 55 , 57C View Figure 57 ). Head projection and basal mandible joint forming antennal cavity. Antennae short, protruding back to body ring 2 ( Figs 55A View Figure 55 , 56A View Figure 56 , 57A View Figure 57 ). Relative lengths of antennomeres: 1<<2>3=4=5<6 ( Figs 55A View Figure 55 , 61A View Figure 61 ). Terminal antennomere with four large sensory cones located together inside a membranous area ( Fig. 61A View Figure 61 ). Antennomere 5 latero-apically with four rows ( Fig. 61B View Figure 61 ), antennomere 6 with two rows ( Fig. 61C View Figure 61 ) of sensilla basiconica.

Gnathochilarium lamellae linguales each with two standard setae located behind one another ( Fig. 55E View Figure 55 ). Stipites each with three apical setae. Mentum not subdivided, basally with several sclerotized ridges ( Figs 55E, F View Figure 55 ). Stipites towards mentum with circa three weakly-developed, sclerotized ledges ( Fig. 55G View Figure 55 ). Hypopharyngeal crest with a field of spine-like structures ( Fig. 61D View Figure 61 ). Central pads of endochilarium separated into two areas, apically with circa eight, basally with>20 sensory cones ( Fig. 61D View Figure 61 ).

Mandible: external tooth simple, rounded; mesal tooth with three well-developed cusps and in some species with an additional fourth, shallow cusp ( Fig. 61E View Figure 61 ). Basal most cusp extraordinarily large and sharp-edged ( Fig. 61E View Figure 61 ). Four or five pectinate lamellae. Molar plate towards pectinate lamellae with a large furrow and circa eight smaller posterior furrows ( Fig. 61E View Figure 61 ).

Collum: smooth, ventrally not protruding as far as ring 2 ( Fig. 57B View Figure 57 ). Collum covering basal mandibular joint anteriorly ( Fig. 55A View Figure 55 ), as well as part of antenna ( Fig. 56A View Figure 56 ).

Body rings: dorsally and laterally with micropunctation, meso- and metazona ventrally with numerous transverse impressions. Ozopores starting at ring 6, touching suture between mesozona and metazona ( Fig. 55A View Figure 55 ).

Telson: preanal process protruding, well-rounded, slightly curved ventrally ( Figs 55C View Figure 55 , 56C View Figure 56 , 57E View Figure 57 , 58C View Figure 58 ). Anal valves short, smooth, with neither grooves, nor lips, nor micropunctation ( Fig. 55C View Figure 55 ). Subanal scale inconspicuous ( Fig. 55C View Figure 55 ).

Legs: coxae 1 and 2 elongated and fused with sternum, podomeres from prefemur to tarsus in both sexes each with 4–10 ventral/mesal setae. Length of midbody legs in males 0.6–0.7 ( Fig. 55H View Figure 55 ), in females 0.4–0.5 times body diameter ( Fig. 55I View Figure 55 ). Each podomere with a long, apical, ventral seta. Coxae 3 and beyond of rectangular shape ( Fig. 55H View Figure 55 ). Tarsus with a tiny dorso-apical seta and a pair of extraordinary long ventral setae ( Figs 55H, I View Figure 55 ).

Male sexual characters: tarsal pads present only on legs 3–7 ( Figs 55B View Figure 55 , 60A View Figure 60 ). Coxae 3–7 without processes, but coxa 7 twice as wide as coxa 6 ( Figs 55B View Figure 55 , 56B View Figure 56 , 57B View Figure 57 ). Ring 7 large, in ventral view twice as wide as normal rings ( Figs 55B View Figure 55 , 57B View Figure 57 ).

Anterior gonopods: prominently elongated, tips projecting from gonopod pouch ( Figs 55B View Figure 55 , 57B View Figure 57 ). Anterior gonopods basally with a small sternal apodeme ( Fig. 55L View Figure 55 ), coxite and telopodite apodeme absent. Sternite always well-developed, but hyaline (sheer), of species-specific shape, either triangular ( Fig. 55L View Figure 55 ), rectangular ( Fig. 56D View Figure 56 ), or well-rounded ( Fig. 60D View Figure 60 ). Coxites wide, in some species mesally with a wide, well-rounded process ( Figs 57E View Figure 57 , 58D View Figure 58 , 59D View Figure 59 ). Telopodites large, elongated ( Fig. 55N View Figure 55 ), mesally protruding into a wide, well-rounded process ( Figs 55N View Figure 55 , 56F View Figure 56 ). Mesal margins of process often large and widely protruding ( Figs 56F View Figure 56 , 58F View Figure 58 ). Margins basally of process in some species additionally protruding ( Fig. 57G View Figure 57 ).

Posterior gonopods resembling long neck and small head of dinosaurs belonging to the Sauropoda group ( Figs 55M, O View Figure 55 ). Coxite and telopodite fused, a suture partially visible ( Fig. 55O View Figure 55 ). Sternite absent ( Figs 55O View Figure 55 , 56G View Figure 56 ), posterior gonopods nevertheless connected via membranes. Coxite conspicuously elongated ( Figs 55O View Figure 55 , 56G View Figure 56 , 57F, H View Figure 57 ), basally at mesal margin with a triangular sclerite, median part of sclerite membranous ( Figs 55O View Figure 55 , 56G View Figure 56 ). Coxite mesally with a single spermatic groove. Telopodites arranged face-to-face with one another, tips bent mesally by 60° ( Fig. 64D View Figure 64 ) or (more often) 90° ( Fig. 55O View Figure 55 ). Apically at lateral margin often with a well-rounded short projection (w in Figs 55M View Figure 55 , 56E View Figure 56 ). Sperm canal apically protruding above telopodite margin (z in Figs 55M View Figure 55 , 56E View Figure 56 ). Telopodite often with an apical process protruding as continuance of tip (x in Figs 55M View Figure 55 , 56E View Figure 56 ). A single membranous lobe (y) often present between (x) and (z) ( Figs 55M View Figure 55 , 56E View Figure 56 ), lobe in one species greatly enlarged ( Fig. 66B View Figure 66 ). Apodeme very long, oriented in 90° angle towards gonopod ( Figs 55O View Figure 55 , 56G View Figure 56 , 59G View Figure 59 ).

Female sexual characters: vulva simple, bivalve-like ( Fig. 55J View Figure 55 ), with a small, poorly sclerotized operculum at base ( Fig. 55K View Figure 55 ). Posterior valve apically slightly overlapping anterior one ( Fig. 61F View Figure 61 ). Both valves smooth, sensory cones absent. Two or three rows of setae basally on each valve ( Fig. 61F View Figure 61 ).

Etymology: Hylekobolus, Latin , masculine, consisting of “hyleko”, short form of hylekoites Greek, m., dweller in wood, which refers to the ecology of this species, and - bolus.