Setoisenoton, Mesibov, Robert, 2010

Mesibov, Robert, 2010, Two new millipede genera from northwest Tasmania, Australia (Diplopoda: Polydesmida: Dalodesmidae), Zootaxa 2571, pp. 53-61 : 54

Setoisenoton , n. gen.

Type species. S. pallidus , n. sp., here designated.

Diagnosis. Small H+19 dalodesmids (ca 5 mm long) with long, straight, non-fused gonopod telopodites ending in a two-process claw in the longitudinal plane, with the prostatic groove terminating in the anterior process.

Etymology. Setoisenoton is Notonesiotes spelled backwards, and points to the contrasting positions of the solenomere in the two genera (see Remarks and Fig. 2 ); masculine gender.

Remarks. The new species described here resembles the H+19 dalodesmid Notonesiotes aucklandensis Johns, 1970 in non-gonopod details, and in both species the gonopod telopodite ends in a two-element claw. N. aucklandensis is known only from the subantarctic Auckland Islands (ca 50°S 166°E), where it is said to be widespread ( Johns 1970). Jeekel (2006) redescribed N. aucklandensis from Auckland Island specimens collected during the Pacific Expedition (1914–1916) of Theodor Mortensen (Zoological Museum, University of Copenhagen). Jeekel showed that in N. aucklandensis the prostatic groove terminates on the posterior process of the claw ( Fig. 2 C). Peter Johns (in litt., 27 July 2010) has very kindly confirmed Jeekel's description and provided me with a photomicrograph of the telopodite of a male N. aucklandensis in the Canterbury Museum (collected at Magnetic Station Cove, Adams Island, Auckland Islands, January 1966); the prostatic groove is clearly visible in the image as it enters the posterior process.

The prostatic groove terminates on the anterior process in the species described here ( Figs 2 A, 2B). If the Tasmanian and Auckland Islands species are closely related, then the prostatic groove has moved from one process to the other within this lineage. I favour the alternative and more conservative view that the two species are not closely related, and that the telopodite similarity is the result of convergent evolution.

Figures

FIGURE 2. (A) Posterior and slightly medial and (B) medial views of right gonopod of Setoisenoton pallidus n. gen., n. sp., paratype male ex QVM 23: 51794. (C) Medial view of right gonopod of Notonesiotes aucklandensis Johns, 1970, redrawn from Fig. 5 in Jeekel (2006). Setation not shown; long dashed lines indicate course of prostatic groove. Scale bar for (A) and (B) = 0.25 mm.