Carinocryptus, Golovatch, 2018

Golovatch, Sergei I., 2018, Further notes on the millipede family Cryptodesmidae in Southeast Asia, with descriptions of a new genus and two new species from Indochina (Diplopoda: Polydesmida), Raffles Bulletin of Zoology 66, pp. 361-370 : 364-365

Carinocryptus , new genus

Diagnosis. A genus of Cryptodesmidae that differs from all other genera of Cryptodesmidae primarily by the peculiar, increasingly high, mid-dorsal, axial rib/carina on postcollum metaterga, coupled with numerous setigerous lobulations and radii at the anterior margin of a typically flabellate collum; a cerotegument crust present on the collum, following metaterga and epiproct; each postcollum metatergum shows several transverse rows of non-differentiated setigerous tuberculations; paraterga are very broad, each paratergum is with an entire anterior margin, a lobulated lateral margin and a multilobate caudal margin; ozopores invisible; the epiproct is conical, the gonopod aperture is obcordate, with slightly elevated lateral and caudal edges; the gonopods in situ are held parallel to each other, with small, squarish, medially fused, very poorly setose coxites and long, slender, typically curved cannulae; the gonopodal telopodites are deeply bipartite and stout, non-circular, both branches being complex and subequal in height, the basal (= main, = caudal) branch has a prominent “prefemoral” (= densely setose) part devoid of any processes and shows a seminal groove running largely on the mesal side, turning laterad only distally before moving onto a distinct, spiniform, simple, retrorse solenomere; the solenophorous (= anterior) branch is more slender and tightly attached to the main branch, with neither a developed accessory seminal chamber nor a hairy pulvillus, but with a long and distinct duct starting at a small node just opposite the solenomere tip and ending up apically on the solenophore.

Type species. Carinocryptus semenyukae sp. n.

Name. To emphasise the apomorphic, evident, mid-dorsal carina on postcollum metaterga; masculine in gender.

Remarks. The new genus is highly peculiar in being the sole representative of Cryptodesmidae that shows the mid-dorsal region of postcollum metaterga not flattened, but carrying a conspicuous, increasingly distinct, axial rib. Moreover, the dorsal tegument of the collum, metaterga and epiproct is clothed with a cerotegument crust.

The presence of these two characters, coupled with a flabellate collum that completely covers the head from above, as well as three transverse rows of tuberculations on each postcollum metatergum and lobulated margins of paraterga are likewise characteristic of the family Pyrgodesmidae , but the latter group usually shows two paramedian dorsal ribs and differentiated tuberculations on metaterga, highly varied and often special pore formulae up to ozopores often being borne on porosteles, and there is no tergal setation. In addition, the medially fused gonopods are typically a pair of globose and hypertophied coxites (with short, normal cannulae) that form a more or less deep gonocoel for the usually highly complex, stout and mainly bi- or tripartite telopodites to hinge into. Similarly, members of the family Haplodesmidae sometimes also have an evident rib and/ or conspicuous outgrowths mid-dorsally on postcollum metaterga, a cerotegument crust, normal pore formulae and ozopores often borne on porosteles, largely also several transverse rows of tuberculations on metaterga, occasionally even a flabellate collum that completely conceals the head in dorsal view. However, haplodesmids contain numerous volvatory forms with clearly enlarged paraterga 2 (vs. only very few in Pyrgodesmidae and none in Cryptodesmidae ) and a relatively small collum (vs. never the case in Pyrgodesmidae or Cryptodesmidae ), as well as peculiar, modified, often 2-segmented tergal setae (shared only with numerous Cryptodesmidae ), while the gonopods show a pair of medially fused, short, subcylindrical coxites with normal cannulae and no gonocoel, whereas the telopodites are slender, elongate, unipartite and relatively simple. Unlike Haplodesmidae , cryptodesmids are never inclined to volvation and always have a large, flabellate, fan-shaped, anteriorly radiate and lobulate collum that completely covers the head from above, normal (broad) paraterga 2, non-differentiated metatergal tuberculations, usually reduced ozopores and, above all, a pair of short, stout, squarish, medially fused gonopodal coxae with particularly slender and relatively long cannulae, and stout, complex, typically uni- or bipartite telopodites.

Amongst Cryptodesmidae , Carinocryptus gen. n. appears to be especially similar to Circulocryptus Golovatch, 2016 , a small Oriental genus (see above), in sharing bipartite gonopodal telopodites and the same general conformation of their main branches, each of which carries a seminal groove running distad largely on the mesal side before moving onto a spiniform, lateral, retrorse solenomere. Moreover, a slender solenophorous branch opposite the solenomere tip shows either a distinct ( Circulocryptus ) or underdeveloped ( Carinocryptus , new genus) accessory seminal chamber and an accessory seminal duct, the latter being either very small, short and running ventrad ( Circulocryptus ) or long, strongly developed, directed distad and ending up apically ( Carinocryptus , new genus). In addition to the above distinguishing somatic characters, the gonopods are subcircular in Circulocryptus , vs. subquadrate in Carinocryptus , new genus.

As noted above, both these genera are sufficiently disjunct to form the new tribe Circulocryptini , tribus nova, of the family Cryptodesmidae , which is distinguished not only within cryptodesmids, but also among all Polydesmida through the development of both an accessory seminal chamber or its anlage and an accessory seminal duct not at or near a spiniform solenomere, but on a separate, anterior branch opposite the solenomere tip.