Dalodesmus hamatus (Brandt, 1841)

Wesener, Thomas, Akkari, Nesrine & Golovatch, Sergei I., 2025, Revision of the millipede family Dalodesmidae in Madagascar, with descriptions of two new Malagasy species of Dalodesmus Cook, 1896 (Diplopoda, Polydesmida), ZooKeys 1223, pp. 185-220 : 185-220

Dalodesmus hamatus (Brandt, 1841)

Figs 5 , 6 , 7 , 8

Polydesmus hamatus Brandt, 1841 a: 10–11 (D); Brandt 1841 b: 140 (D); Gervais 1847: 114 (D); Attems 1940: 493 (L); Golovatch and Hoffman 2000: 237 (L).

Non Polydesmus (Tubercularium) sakalava – de Saussure and Zehntner 1902: 93 (N).

Dalodesmus hamatus – Golovatch and Hoffman 1989: 160, figs 1–6 (D); 2000: 237 (L); Enghoff 2003: 623 (L); Wesener and Enghoff 2022: 926 (L).

Note.

The ♀ holotype, currently housed in the ZISP collection and coming from an unspecified locality, presumably in Madagascar, has been revised, properly redescribed, and illustrated ( Golovatch and Hoffman 1989).

New material examined.

• ♂ ( ZFMK MYR 13631 ), Madagascar, Toamasina Province, Analanjirofo, Makira Natural Park, ca 44.5 km NW of Maroantsetra, Antainambalana River tributary, 1 km around coordinates, 15°4'15"S, 49°34'48"E, 240–670 m, primary lowland rainforest on basalt, 30. VIII. – 08. IX. 2023, D. Telnov leg. • 2 ♀ ( ZFMK MYR 13629 ), same data as previous • 2 ♀ ( ZFMK MYR 13630 ), with eggs, same data as male • 1 ♀ ( NHML), same data as male .

Diagnosis.

Tips of paraterga mostly sharp and projecting past posterior tergal margin, as in D. odontopezus , D. orator , vs wider and not projecting past rear tergal margin in D. speophilus sp. nov., D. tectus , and D. kompantsevi sp. nov. Colour uniformly dark grey to blackish, paraterga not yellow as opposed to D. odontopezus and D. orator . Both latter species with a male body length of 26–28 mm that is larger than D. hamatus with 20 mm male and 22–24 mm females. See also the key below.

Identity of the new material of D. hamatus .

The ♀ holotype (after Golovatch and Hoffman 1989) has a similar size (length ~ 22 mm, width 2.9 mm) to the newly discovered material. Its colouration is rusty brown (dry specimen, probably faded). The habitus with the paraterga clearly upturned above the dorsum (Fig. 5 A – D ), dorsal surface between midbody paraterga largely areate, polygonal bosses mostly being clearly obliterated (Fig. 5 B ), this being identical to the new material. While the type locality of D. hamatus is just “ Madagascar ”, the newly discovered locality in Makira Natural Park also included specimens of the very large (> 200 mm) spirostreptid Analacostreptus sculptus ( de Saussure & Zehntner, 1902) , another species otherwise known only from “ Madagascar ”.

Redescription.

(Based on fresh material from Makira.) Length ~ 20 mm (n = 1), width of midbody pro- and metazona 1.7 and 3.9 mm (n = 1), respectively (♂), ♀♀ 22–24 mm long (n = 3), width of prozona 1.9–2.3 mm (n = 1), of metazona 4.1–4.3 mm (n = 4).

Colouration, after less than 6 months of preservation in alcohol, dark grey to blackish, collum faded brown, head brown, epicranium grey, legs pale grey; antennae dark brown (Fig. 6 A – C ).

Body with 20 rings. Tegument mainly dull, microgranulate to microtuberculate throughout (Figs 5 A – D , 6 A – C , 7 A – D ), even surfaces of prozona and of metazona below paraterga finely microgranulate, sterna granulate. Head also densely microtuberculate or granulate throughout, micropilose up to level of antennae; epicranial suture thin, but distinct; genae squarish, set off ventrally from gnathochilarial stipes by a small, but evident ridge. Interantennal isthmus ~ 2 × diameter of antennal socket. Antennae short and rather clavate, in situ reaching in both sexes back past ring 4 when stretched dorsally, very densely setose and microgranulate. In length, antennomere 6> 3> 5> 4 = 2> 1 = 7; antennomere 6 the largest and the highest, antennomeres 5 and 6 each with a small, round, distodorsal knob, most likely beset with sensory cones. In width, collum ≤ head <ring 2 = 3 <4–16; thereafter body gradually tapering towards telson (Fig. 6 A – C ). Collum transversely suboval, regularly and broadly rounded laterally, densely tuberculate, most tubercles slightly oblong-oval, evident, equipped with very short, mostly subclavate setae and arranged in 16–17 lateral, 6 transverse, rather irregular, arcuated rows. Metaterga 2–4 narrow, each with 3–4 similar transverse arcuated rows of setigerous tubercles, following metaterga each largely with 4–5 such rows (Fig. 7 A, B ). Paraterga well-developed, set high (mostly at upper ¼ body), upturned to subhorizontal, thus leaving the dorsum only faintly convex (Fig. 7 B ); anterior and posterior margins of paraterga 2 and 3 clearly drawn forward and caudad, respectively, following paraterga drawn increasingly only caudad (Fig. 6 A – C ); caudal corners sharp, produced past rear tergal margin; caudal margins of paraterga with five oblong projections (Fig. 7 B ). Lateral margins of paraterga beset with numerous, similarly oblong and usually subequal, setigerous tubercles / lobulations. Ozopores inconspicuous, opening dorsally near penultimate lateral lobulation on pore-baring rings 5, 7, 9, 10, 12, 13, 15–19. Strictures between pro- and metazona narrow and rather deep, nearly smooth.

Telson: Epiproct small, conical and subtruncate at tip. Paraprocts with 2 + 2 setae on triangular, projections / knobs (Figs 5 C , 6 C ). Hypoproct trapeziform, with 1 + 1 setae borne on distinct oblong knobs at caudal margin.

Limbus very thin, small, and entire. Neither an axial line nor pleurosternal carinae (Fig. 7 A – C ). Endotergum inconspicuous, posterior margin of metazona projecting into long, sharp, apically microdenticulate, triangular projections (Fig. 7 F ).

Gonopodal aperture roundly pentagonal, relatively small, taking up ~ 1 / 2 width of metazonum 7, clearly open and drawn into metazonum 6.

Midbody legs incrassate, rather long. 1.4–1.5 × as long as body height, with small, stout, abundant and usually curved setae with admixture of sphaerotrichomes ventrally on all podomeres (♂, Fig. 7 E ); gonopores on ♂ coxae 2 inconspicuous, each borne on a very small swelling (♂); prefemora not bulged laterally; claws simple and very small; in length, tarsus> femur> prefemur> tibia> postfemur> coxa.

Gonopods (Figs 6 D – G , 8 A – I ) very slender and long, tips in situ reaching anteriorly until coxae 5. Both coxites and prefemorites (= densely setose parts of telopodites) equally very short and stout, fused medially, the former fully and the latter mostly hidden inside gonopodal aperture. Femorites (fe) contiguous medially in basal 1 / 3, setose almost all along, both slightly diverging distad towards acropodites. Apical portions of each telopodite (= acropodites) clearly diverging, rather simple and compact, curved ventrad and clearly divided into three unequal branches: a short, slightly curved, submesal, tubiform, simple and non-sigmoid solenomere (sl) flanked by a rather simple, 2 - branched solenophore, this latter being represented by a flagelliform, slightly barbed, short and acuminate lateral branch (lb), and a particularly large, lobe-shaped, acuminate and membranous mesal branch (mb) with a tooth near base.

Figures

Figure 5. Dalodesmus hamatus (Brandt, 1841), ♀ holotype A anterior part of body, dorsal view B right half of metazonum 10, dorsal view C posterior end of body, dorsal view D body ring 9, oral view E leg 2 and epigynal lobe, ventral view F midbody leg, lateral view. Scale bars: 1000 µm (after Golovatch and Hoffman 1989).

Figure 6. Dalodesmus hamatus (Brandt, 1841), ♂ from Makira (ZFMK MYR 13631). Multi-layer photographs A anterior body, dorsal view B midbody, dorsal view C telson, dorsal view E gonopods, posterior view E gonopods, anterior view F gonopods, lateral view G right gonopod, mesal view. Abbreviations: lb = lateral branch; mb = mesal branch; sl = solenomere branch. Scale bars: 1000 µm.

Figure 7. Dalodesmus hamatus (Brandt, 1841), ♂ from Makira (ZFMK MYR 13631). SEM micrographs A midbody ring with pro- and metazonite, dorsal view B midbody ring, lateral view C details of surface structures of prozonite and metazonite D details of surface structures, dorsal view E tarsus of midbody leg F endotergum. Scale bars: 1000 µm (A); 200 µm (B); 100 µm (C, E); 30 µm (D); 0 µm (F).

Figure 8. Dalodesmus hamatus (Brandt, 1841), ♂ from Makira (ZFMK MYR 13631). SEM micrographs. Gonopod, A = right B – I = left. A Right, anterior view B left, anterior view C lateral view D posteromesal view E posterior view F acropodite, anterior view G acropodite, lateral view H acropodite, posteromesal view I acropodite, mesal view. Abbreviations: fe = femorite; lb = lateral branch; mb = mesal branch; sl = solenomere branch. Scale bars: 100 µm.