Tancitares Chamberlin

Hoffman, Richard L., 2011, The curious genitalic structures of Tancitares michoacanus (Polydesmida, Rhachodesmidae), International Journal of Myriapodology 5, pp. 27-33 : 28-29

Genus Tancitares Chamberlin

Tancitares Chamberlin, 1942, Proc. Biol. Soc. Washington 55: 58. - Loomis, 1968, U. S. Nat. Mus. Bull. 266: 41. - Hoffman, 1999, Va. Mus. Nat. Hist. Spec. Publ. 8: 429.

Type species.

Tancitares michoacanus Chamberlin, by original designation and monotypy.

Diagnosis.

Males of the type species are distinguished from all other rhachodesmids by the occurrence of digitiform accessory processes on the coxae of the second pair of legs (Fig. 3), and by the reduction of the soleniferous element of the gonotelopodite to a vestigial basal remnant, with hypertrophy of the remaining telopodite (Fig. 7). Females may be recognized by the elongated tubular form of the female genitalia and modified pleurosternal region of the 3rd segment (Fig. 10).

Range.

The genus is known only from the western part of the Mexican transverse volcanic belt in Michoacán and Colima.

Affinities.

Among the ranks of established rhachodesmid genera, only one is a possible close relative of Tancitares : the rather poorly-known genus Pararhachistes Pocock (1909) which was proposed for two species ( Pararhachistes elevatus and Pararhachistes vertebratus ) from the coastal mountains of Guerrero. Pocock’s illustrations (1909: pls. 12, 13) portray a general similarity in body form, the large size of the gonopod aperture, and small secondary processes on the male 2nd coxae. The figure of the gonopod of elevatus (reproduced here as Fig. 8), indicates a slender, sinuous process just distad of the basal fossa that might be the homologue of the solenomere in Tancitares . Unfortunately the type material of Pocock’s two species was not found during several personal searches of the British Museum myriapod collection, and may be presumed lost, denying the opportunity for an examination with higher magnification. Eventually topotypic material may become available. A third nominal species, Pararhachistes amblus Chamberlin (1942b) is known to me from a male paratype. This species is not congeneric with those named by Pocock, differing inter alia in that the efferent duct extends to the apex of the telopodite and is not carried on a slender basal solenomere. Lastly, two other species (galeanae and potosinus) named in Pararhachistes by Chamberlin (1943), were based on female specimens which cannot be assigned to any genus with present knowledge of this family. Their geographic origin (San Luis Potosí and Nuevo León) argues against their placement in either Pararhachistes or Tancitares .