Tidesmus torreyanus ( Loomis, 1960 ) Loomis, 1960

Shear, William A. & Shelley, Rowland M., 2007, The milliped genus Tidesmus Chamberlin, 1943 (Polydesmida: Macrosternodesmidae), Zootaxa 1656, pp. 51-68 : 60-61

Tidesmus torreyanus ( Loomis, 1960) , new combination

Figs. 9–12 .

Phreatodesmus torreyanus Loomis 1960:63 , figs. 8–11. Buckett, 1964:12. Hoffman, 1999:470. Shelley, 2002b:107. Phreatodesmus dentatus Loomis 1960:64 , fig. 13. Buckett, 1964:12. Hoffman, 1999:470. Shelley, 2002b:107. New Synonymy.

Type specimens. Of P. torreyanus , male holotype and ca. 13 female & juvenile paratypes ( USNM) and 1 male paratype ( VMNH) collected by O. F. Cook, 29 November 1925, in a garden at Torrey Pines State Beach and Reserve, ca. 4.5 mi (7.2 km) N La Jolla, San Diego Co., California. Of P. dentatus , male holotype and 1 female and ca. 9 juvenile female paratypes ( USNM) collected by O. F. Cook, 14 February 1929, 7 mi. W Cajon on Big Pine Road in Cajon Pass, Angeles National Forest, San Bernardino Co., California.

Diagnosis. Process B overhanging essentially entire ventral surface of acropodite, terminating over medial margin, apically falcate or sigmoid with tip directed toward or away from acropodal stem, with flange distal to midlength and more distal tooth on inner margin, basal subbranch short and subtriangular; acropodite without true distal zone, margin bent variably caudad.

Description. Agreeing closely with T. variabilis in somatic features with following exceptions: Setae on collum arranged in three well defined rows. Prozonites glabrous, entirely without setae. Transverse metatergal grooves faint, evident on 7th–16th metaterga.

Gonopods in situ ( Fig. 9 ) not completely filling respective halves of aperture, prefemora not contiguous in midline. Gonopod structure as follows ( Figs. 9–12 ): Coxa as described for T. episcopus . Prefemur (pf, Fig. 9 ) subhorizontal, process B (b, Figs. 10, 12 ) extending laterad basally then curving broadly ventromediad and overhanging entire ventral surface of acropodite (ac, Figs. 9, 10 ), apically falcate or sigmoid, terminating over medial acropodal margin, with short basal subbranch, flange on caudal surface distal to midlength, and blunt tooth on inner margin distal to flange; distal margin of acropodite bent abruptly caudomediad forming "shoul- der" on caudal margin, with medially directed spine on anterior edge, and shorter, acuminate projections in between; solenomere (s, Fig. 12 ) relatively short, apically uncinate.

Va r ia ti o n. The few available males with gonopods from Pacific coastal localities agree closely with those of the holotype. The holotype of P. dentatus , however, differs in that the basal subbranch of process B is larger and the apical curvature of process B is sigmoid with the tip directed dorsad, away from acropodal stem. The male from Arizona differs from all the California males in that process B does not extend as far over the ventral surface of the acropodite, and the apical curvature is less sigmoid; the overall length of process B is somewhat intermediate between those of T. episcopus and T. torreyanus .

Habitat. Unknown.

Distribution. Southern California, USA, and northern Baja California Norté, Mexico, extending from Cajon Pass in the San Bernardino Mountains to the Pacific Coast north of San Diego and southward essentially as far as Ensenada; also with an allopatric population in southeastern Arizona, some 475 mi (760 km) to the east-southeast. The California and Mexico localities cover a distance of ca. 170 mi (272 km), and the known range along the Pacific Coast extends for 75 mi (120 km); the sample from Cajon Pass is some 95 mi (152 km) north-northeast of the northernmost coastal site. As the Dragoon Mountains in Arizona are only around 50 mi (80 km) west of New Mexico, T. torreyanus can be reasonably expected in the Peloncillo Mountains of Hidalgo Co. in that state. In addition to the types, the following samples are available:

USA: CALIFORNIA: San Diego Co., Torrey Pines State Reserve, ca. 4.5 mi (7.2 km) N La Jolla, m, 2 ff, 1 November 1925, Hardy (VMNH).

ARIZONA: Cochise Co., Dragoon Mountains (Coronado National Forest) near Dragoon, m, date unknown, H. F. Loomis (FSCA).

MEXICO: BAJA CALIFORNIA NORTÉ: "Wharf Gulley 20 mi down" (=? coastal site ca. 20 mi (32 km) S of US Border), m (gonopods lost), 4 January 1925, O. F. Cook (VMNH); and 14.5 mi (23.2 km) N Ensenada (= ca. 33.5 mi [53.6 km] S of US border), m, 7 January 1925, O. F. Cook (VMNH).

Remarks. The name dentatus was assigned to the variant from Cajon pass, which may represent a separate subspecies; however, documentation of this status by intermediate or intergrade specimens is not presently possible, so we combine the names. From a geographical standpoint, both samples from Riverside Co., California, listed under " Tidesmus spp." in the concluding account likely refer to T. torreyanus and that from Temescal Canyon is from a somewhat intermediate location and might constitute an intermediate form, but the gonopods are missing. As tiny as these millipedes are and as difficult as they are to find, we may never have solid documentation of subspecific or specific statuses. One could even legitimately argue for a single California species with torreyanus and dentatus being subspecies of episcopus , but we believe that association of torreyanus and dentatus in a separate species is defendable by the flanges, distal teeth, and basal branches on processes B, which are absent from episcopus .

While its gonopods differ as described above under "Variation," we nonetheless assign the Arizona male to T. torreyanus , the named species that it most closely resembles. This action seems preferable to naming and describing a dubious new species, the only other option.

The VMNH samples from Mexico 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).

Figures

FIGURES 9 – 12. Tidesmus torreyanus gonopods in situ. 9, ventral view. 10, anteroventral view. 11, posterior view. 12, anterior view.