Tancitares michoacanus Chamberlin

Hoffman, Richard L., 2011, The curious genitalic structures of Tancitares michoacanus (Polydesmida, Rhachodesmidae), International Journal of Myriapodology 5, pp. 27-33 : 29-31

Tancitares michoacanus Chamberlin Figs 179, 10

Tancitares michoacanus Chamberlin, 1942, Proc. Biol. Soc. Washington, 55: 58, fig. 7. Male holotype, one male and two female topoparatypes (USNM), one male paratype (VMNH) from Pedregal, 6000 ft., Cerro Tancítaro, Michoacán, Mexico; H. Hoogstraal leg. 28 June 1941 (Comment 1).

Material.

The type series, also: Mexico: Colima: "8 mi. NW of Colima", 25 July 1963, Donald R. Whitehead (VMNH 1/0).

Description.

Paratype male (VMNH), length not measurable (specimen fragmented), W ca. 2.8 mm; body parallel-sided over most of length, collum and segments 2-4 slightly narrower than 5. Color, shortly after preservation (teste Chamberlin 1942a): dorsally brown, with caudal margin of metaterga medially yellow, paranota of segments 1-5 and the poriferous paranota thereafter yellow, legs light brown proximally, yellowish distally.

Head and gnathochilarium unmodified. Paranota relatively small and set high on sides, overlapping on anterior segments, moderately separated at midbody, slightly elevated above horizontal; anterior and posterior corners broadly rounded on anterior segments (Fig. 1), posterior corners of poriferous segment beyond midbody notably beveled, marginal peritreme terminating at level of ozopores, not continued to posterior angle (Fig. 2). Pore distribution normal. Metaterga without transverse sulcus, surface densely and coarsely punctate, becoming granulate on paranota, caudal edge with a row of 6 to 8 small tubercles. Stricture not costulate, anterior edge sharply defined. Segment 20 broadly triangular, paraprocts and hypoproct unmodified. Segments ventrally elevated as podosterna, each with moderately deep transverse groove, no subcoxal projections. Sides of metazona notably coriarious. Stigmata small, rounded, in normal polydesmoid positions. Legs long, sparsely setose, without distal tibial or tarsal pads or other modifications.

Sterna of anterior segments narrow, unmodified. Coxae of 2nd pair of legs (Fig. 3) with prominent, digitiform, anteriorly-directed processes originating at bases of gonapophyses, latter long, slender, distally setose.

Gonopod aperture large, subquadrate, narrowing both stricture and prozonum, sternum of 7th segment with two conical setose processes (Fig. 4). Gonopods retracted into body cavity, only apices of coxae visible; no median sternal sclerite. Transverse muscle between sternal apodemes not evident. Coxae reduced in size, without setae, no trace of cannula or its internal musculature (Comment 2). Telopodites long and slender, extending anterior between legs of 5th segment, their apices interlocked (Fig. 4). Basal region globose, with large internal chamber lined with dense short setae, opening on mesal side of base. Edge of cavity/fossa continued as an acuminate, recurved process carrying the efferent duct (Fig. 7). Remainder of telopodite a slender, curved branch with acute terminus and a sigmoidally curved, retrorse subapical process (Fig. 6) on mesal side.

Female genitalia notably modified: sterna region of 3rd segment strongly prolonged ventrad forming a sheath partly surrounding coxae of 2nd legs and cyphopods, coxae prolonged ventrad as subconical processes (Fig. 9). Cyphopods elongate, tubular, entirely membranous, no basal sclerotized element (receptacle) observed (Fig. 10) (valves may be strongly reduced and concealed at ends of tubular region) (Comment 3).