Tidesmus variabilis Loomis 1960, new combination
Creators: name: Shear, William A.
name: Shelley, Rowland M.
Publisher: name: Zenodo
Year: 2007
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Diplopoda
Polydesmida
Tidesmus
Tidesmus variabilis

description: Tidesmus variabilis (Loomis, 1960), new combination
Figs. 5–8, 13–21
Oodedesmus variabilis Loomis, 1960:60, figs. 6–7. Hoffman, 1999:469 –470.
Type specimens. male holotype and 1 male & 2 female paratypes (USNM) collected by H. F. Loomis, 21 January 1923, along Fish Creek (a tributary of the Salt River), ca. 5 mi (8 km) NE Tortilla Flat, Maricopa Co., Arizona.
Diagnosis. Process B overhanging lateral margin of acropodite, with flange distal to midlength but without distal tooth, basal lobe long and narrow, extending ventrad beyond outermost point of process; acropodite with true distal zone prolonged beyond origin of solenomere and expanding into anterior and caudal branches.
Description. Length 11.4–12.0 mm, width 1.6–2.5 mm. All regions of head densely pilose with short, parallel-sided setae; antennae reaching back to around caudal margin of 2nd metatergite, comprising seven densely pilose articles, relative lengths of antennomeres 2>3>6>5>4>7>1, 1 subglobose, 2–5 clavate, 6 subovoid and swollen, 7 truncate with 4 terminal sensory cones, no other sensory structures evident. Collum (Fig. 13) short, not overlapping epicranium, surface granular, giving rise to clavate setae in five poorly defined rows. Prozonites smooth on pregonopodal segments, lightly costulate in midbody region, becoming granular to smooth caudad, occasionally giving rise to clavate setae (Figs. 18, 19). 2nd–7th metatergites (Fig. 13) generally smooth, with three faintly delineated rows of clavate setae arising from low, rounded to lightly conical pustules, 4th–7th metaterga (Figs. 13, 15) also with shallow, moderately distinct, transverse grooves between 1st and 2nd rows of pustules; 8th–18th metaterga (Fig. 16) with grooves sharper & more distinct, and four rows of setae arising from pustules; 19th metatergite (Fig. 18) shorter and with faint groove. Limbi (Fig. 19) deeply serrate with one part as elongated bristle. Paranota short but distinct, margins generally smooth on pregonopodal segments, with three short teeth on segments 8–17; ozopores opening in short caudolateral swellings on segments 5, 7, 9–10, 12, 13, and 15–19. Epiproct (Fig. 17) bluntly subtriangular, overhanging but not extending beyond level of paraprocts, surface generally smooth, with four poorly defined rows of pustules giving rise to clavate setae and 4 long, thin, additional setae arising terminally & subterminally; paraprocts granular, with at most only a few scattered setae; hypoproct short & rounded, with a pair of long, thin, parallel-sided, apical setae.
Pregonopodal sterna (Fig. 14) with at most only faint elevations between leg pairs, otherwise without modifications; postgonopodal sterna with only low elevations between legs. 1st legs short, crassate; legs 2–7 (Fig. 14) longer and slightly less crassate, dorsal surfaces of prefemora swollen & rounded; postgonopodal legs continuing through segment 18, prefemoral swellings becoming progressively shorter and more lobe-like caudally; all legs moderately hirsute, distal articles more so; tarsal claws short & gently curved, apically acuminate.
Gonopodal aperture (Fig. 14) extending caudad between 9th legs, caudal margin elevated and flared. Gonopod structure as follows (Figs. 4–8, 20–21): Coxa as in T. episcopus. Prefemur (pf, Fig. 20) angling generally ventrad, subhorizontal basally in some males, process B (b1 and b2, Figs. 20, 21) extending laterad basally then bending ventromediad and overhanging ventrolateral margin of acropodite, bent sharply dorsad apically and with moderate-size flange on lateral margin distal to bend, basal lobe (b2, Figs. 20–21) long and narrow, expanding slightly at midlength then tapering distad, extending ventrad to level of or even beyond outermost point of process, crossing opposite member in situ; distal margin of acropodite prolonged into two branches thereby constituting true distal zone, extending ventrad beyond origin of solenomere (s, Figs. 20, 21), anterior branch (sp, Figs. 20, 21) variably narrow to blade-like, curving broadly anteriad and recurved apically, possibly partly enveloping main branch of process B, caudal branch variably subspatulate, expanding and curving distomediad and partly enclosing main branch of process B, margin lightly irregular; solenomere relatively long and lightly bisinuate, extending ventrad.
Va r ia ti o n. Variation in T. variabilis involves the relative lengths of all branches other than the solenomere and the breadths of the acropodal projections that constitute the distal zone. The males from between Miami and Superior, Pinal/ Gila cos., agree closely with the holotype except for the breadths and angles of the branches of the distal zone. In that from Prescott, Yavapai Co., the anterior branch is narrower than those in the types or the males from Pinal/ Gila cos., so as to appear as yet another separate projection apart from the caudal branch.
Habitat. Unknown.
Distribution. Central Arizona; occurring in the Prescott, Coconino, and Tonto National Forests from central Yavapai to northern Pinal/ Gila cos., a distance of roughly 125 mi (200 km) in a northwestern-southeastern direction. The samples from Pinal/ Gila cos. are only ca. 20 mi (32 km) south of the type locality, and because of its proximity to the male from Prescott, ca. 40 mi (64 km) to the west-southwest, we include the juvenile sample from Rimrock under T. variabilis. In addition to the types, the following samples were examined:
ARIZONA: Maricopa Co., along Fish Cr. ca. 5 mi (8 km) NE Tortilla Flat, m, February 1924, H. F. Loomis (VMNH). Pinal/ Gila cos., along US hwy. 60 between Miami and Superior, m, ca. 9 ff, juvs., 1 March 1925, H. F. & E. M. Loomis (VMNH) and 2 mm, ca. 9 ff, juvs., 25 July 1976, A. K. Johnson (NCSM). Yavapai Co., Prescott, m, ca. 16 ff, juvs., 9 August 1930, H. F. Loomis (VMNH); and Rimrock, V Bar V Ranch, juvs., 8 April 1976, K. Silivari (NCSM).
Remarks. The gonopod of T. variabilis is highly complex with five separate branches and flanges extending subventrad; when paired with its counterpart in situ, 10 projections emanate from the anterior position on segment 7, some of which cross each other. Consequently, it is difficult to comprehend the gonopodal structure in situ or even to determine which projections arise from which gonopod. Despite this complexity, the gonopod is just an extreme manifestation of the basic generic pattern exemplified by T. episcopus. Though not helpful in determining the acropodal configuration, this pattern of several branches and lamellae extending ventrad is another justification for assigning B. hastingsus to Tidesmus (see subsequent account), as the two incomprehensible illustrations accompanying the original description (Chamberlin 1941:39, figs. 48–49) show several projections arising from a large, subglobose coxa, in a pattern that conceivably could apply to variabilis.
The samples from the VMNH were in a jar labeled " PARATYPES " but were not so designated by Loomis (1960) in the original description and hence do not hold this status (Article 72.4.6 of the Code).
description: Published as part of Shear, William A. & Shelley, Rowland M., 2007, The milliped genus Tidesmus Chamberlin, 1943 (Polydesmida: Macrosternodesmidae), pp. 51-68 in Zootaxa 1656 on pages 58-59, DOI: 10.5281/zenodo.179846