Gonatodesmus, Golovatch, Sergei I., Geoffroy, Jean-Jacques & VandenSpiegel, Didier, 2014

Golovatch, Sergei I., Geoffroy, Jean-Jacques & VandenSpiegel, Didier, 2014, Review of the millipede family Trichopolydesmidae in the Oriental realm (Diplopoda, Polydesmida), with descriptions of new genera and species, ZooKeys 414, pp. 19-65 : 47-48

Gonatodesmus gen. n.

Diagnosis.

19 segments (♂, ♀); pore formula normal: 5, 7, 9, 10, 12, 13, 15-18; ♂ head with a considerable, rounded, central hump above antennae; paraterga poorly developed, serrate/microdentate at lateral edge, with 3 rows of 3+3 or 4+4, long, bacilliform setae (regardless of lateral setae); gonopod coxae with gonocoel not deep; telopodites clearly exposed, but lying rather tightly appressed and mostly parallel to venter, unipartite, slender, abruptly geniculate and directed laterad distal to prefemoral parts, the latter about half as long as telopodites, held parallel to main axis, each set off from a twisted acropodite by a geniculation cingulum (c); acropodites elongate, near midway with a remarkably large hairy pulvillus (p) on top of a small accessory seminal chamber; neither a separate solenophore branch nor a solenomere. Seminal groove (sg) running mostly on mesal side, turning caudad (= ventrad) only beyond geniculation.

Name.

To emphasize the geniculated gonopod telopodite (γόνατο meaning "a knee" in Greek), masculine.

Type species.

Gonatodesmus communicans sp. n., by present designation.

Remarks.

This new genus is highly disjunct in being the sole member of the family which shows a remarkable midway geniculation of the gonopod telopodite. The gonopod tip being directed laterad is not unique in Trichopolydesmidae , shared also with Aporodesmella tergalis sp. n. However, the entire distal, post-geniculation half of the gonopod in Gonatodesmus gen. n. is obviously twisted and strongly elongate, also showing a remarkably distinct hairy pulvillus on top of a small, but evident accessory seminal chamber. Only vestiges of the latter are occasionally observed in a couple of Euro-Mediterranean genera of Trichopolydesmidae ( Golovatch 2013), whereas an obvious hairy pulvillus seems to be singular in the family. In contrast, such a gonopod conformation vividly resembles the conditions largely characterizing the family Opisotretidae ( Golovatch et al. 2013), but the prefemoral parts in Gonatodesmus gen. n. are clearly elongate and held parallel to the main axis while the acropodites distal to the unique geniculation are yet relatively short to be directed dorsolaterad. So the assignment of Gonatodesmus gen. n. to Trichopolydesmidae , not Opisotretidae , is preferred. However, one may justly regard Gonatodesmus gen. n. as a kind of transition or bridge between these two families of Trichopolydesmoidea . This new genus rather demonstrates an evolutionary trend from the more basal Trichopolydesmidae towards the advanced Opisotretidae .