Tynommatidae Hoffman, 1980

Shelley, Rowland M. & Richart, Casey H., 2014, Tynommatidae, n. stat., a family of western North American millipeds: Hypotheses on origins and affinities; tribal elevations; rediagnoses of Diactis Loomis, 1937, and Florea and Caliactis, both Shelley, 1996; and description of D. hedini, n. sp. (Callipodida: Schizopetalidea), Insecta Mundi 2014 (340), pp. 1-19 : 3

Family Tynommatidae Hoffman, 1980 , new status

Tynommatinae Hoffman, 1980:120 ; 1999:200. Shelley, 1996:30; 2002a:105. Shelley et al. 2000:60. Stoev et al., 2008:35. Stoev and Shelley, 2009:160–161.

Diagnosis (adapted from that in Stoev and Shelley [2009]; terminology of Shelley [1996]). Small- to moderate-size Schizopetalidea with or without light lateral stripes along pleurotergal suture in addition to middorsal one. Carinae large and prominent, transition point varying from pleuroterga 7–19. Gonosterna with or without lateral sternal laminae and variable caudal sternal processes; gonocoxae also with or without processes. Telopodites weakly sclerotized, arising caudally or anteriorly from coxae, generally long, slender, fragile, and sublinear, subupright or leaning, not strongly bent near midlength or distad, with or without true prefemoral processes and proximal projections, divided distad (division point) into two or three branches; solenomere branch usually subterminal, subdivided into ventral solenomere and dorsal branch ‘A’; distal telopodal branch (tibiotarsus) short, configuration varying from expanded and laminate to narrow and gently curved, with or without a third branch, ‘B’, apparently representing relocated prefemoral process.

Components. Five subfamilies – Tynommatinae and Colactidinae both by Hoffman, 1980; Texophoninae Shelley, 1989 ; Diactidinae Shelley, 1996 ; and Aspidiophoninae Shelley, 2000 – the last four constituting tribal elevations and new statuses.

Distribution. Tynommatidae inhabit three or perhaps four disjunct areas (Shelley 1989, 1996; Hoffman 1999; Shear et al. 2003; Stoev et al. 2008; Shelley and Golovatch 2011). The smallest extends along the Gulf Coast of south Texas from San Patricio to Cameron counties (cos.) and is occupied by the two species of Texophon (Texophoninae) . As only three specific localities are involved, two in Cameron and one in San Patricio cos., some 224 km (140 mi) apart, texophonines do not seem continuous but are considered so herein. The second largest area surrounds San Francisco Bay, California, extends along the Pacific coast from northcentral Sonoma to San Luis Obispo cos., ranges inland to San Joaquin Co., and is occupied by the three species of Tynomma . The third and largest area, harboring all other taxa, extends discontinuously from Kern and Los Angeles cos., California, USA, to southern Baja California Sur and Durango / Sinaloa, Mexico. Extensive sampling has taken place to the north in coastal California and in the Dixie and Fishlake National Forests (Nat. Fors.), in southwestern/southcentral Utah, such that northern range limits in these states seem well defined, but the eastern boundary in New Mexico, USA, and the southern in Durango / Sinaloa, Mexico, are nebulous. Tynommatidae probably occupy adjoining Nyarit, Jalisco, and Zacatecas, and Texophoninae may inhabit coastal Tamaulipas, particularly across the Rio Grande opposite Brownsville, Cameron Co., Texas.

Relationships. See concluding section.

Remarks. Though five names, four elevated herein, have been validly proposed, subfamilial categories in Tynommatidae are actually uncertain, and we endorse the decision ( Stoev and Shelley 2009) not to assign Mexicopetalum . Except for Nevada, areas in the US that are reasonably potential for Tynommatidae have been sufficiently sampled that all generic- and higher-level taxa have probably been discovered, but the same cannot be said about potential areas in Mexico. Vast regions in states known to harbor tynommatids (Baja California Norte and Sur, Sonora, Chihuahua, Durango, Sinaloa) are poorly sampled for diplopods in general, so new tynommatids surely await discovery; as more and more Mexican forms are found, bizarre and unique telopodites that appear to warrant new genera, tribes, and perhaps even subfamilies are virtually guaranteed. The overall picture of Mexican Tynommatidae will gradually become evident, so to avoid having to synonymize superfluous supra-generic names, we think new ones should be deferred until gonopodal patterns come into focus. The three most recent discoveries required monotypic genera – Colactoides , Aspidiophon , and Mexicopetalum – but only the first was assignable to an established higher category, Colactidini (now Colactidinae ) ( Shelley 1997, 2000; Stoev et al. 2008; Stoev and Shelley 2009). The monotypic tribe Aspidiophonini (now Aspidiophoninae ) was erected for its namesake, and one could have been justified for Mexicopetalum had the authors so chosen. Tynommatids possess complex, plastic gonopods ( Hoffman 1980), and as D. hedini indicates for the diactidine prefemoral process, sub-structures have been added, lost, rearranged, reconfigured, and relocated, creating a tangled, intricate picture. Until more Mexican tynommatids are available, gonopodal patterns are better understood, and informed supra-generic categories can be proposed, we think that erecting them “piece-meal,” essentially a new one for each newly discovered form, is imprudent. Deferring them seems preferable to individual proposals and having to combine and synonymize names years later.