Rhachodesmidae Carl 1903

Shelley, Rowland M., Espino, Ancelmo Orona & Robles, Miguel Ángel Gallegos, 2015, A contribution on the Middle American milliped family Rhachodesmidae (Polydesmida: Leptodesmidea: Rhachodesmoidea): description of Tiphallus torreon n. sp., the first species from Coahuila, Mexico; first records from Belize; and depiction of the (super) familial distribution, Insecta Mundi 2015 (423), pp. 1-10 : 2-3

Family Rhachodesmidae Carl 1903

Diagnosis (adapted from those of Shear [1973] and Hoffman [1982]). Small to moderate-size, often spectacularly colorful, Rhachodesmoidea with transversely ovoid collums; paranota varying from slight longitudinal ridges to large, subquadrate flanges, rarely slender and subspiniform. Gonopods without cannulae and prefemoral processes; prefemoral telopodital regions densely and subuniformly pilose, fossas usually large, deeply excavated, and with long marginal hairs; acropodites without superficial subdivisions.

Components. Seventeen genera are presently recognized; Hoffman (1999) listed 16 but overlooked Tiphallus .

Distribution. Rhachodesmidae’s distribution – northeastern Mexico to central Costa Rica – is also that of Rhachodesmoidea ; Tridontomidae occupy a small enclave in Alta Verapaz Department (Dept.), Guatemala, in the heart of this area ( Fig. 2 ). Like Glomeridae (Glomerida) , Platydesmidae (Platydesmida) , and Stemmiulidae (Stemmiulida) ( Shelley and Golovatch 2011, Shelley et al. 2012), Rhachodesmidae extend northward along the Gulf Coast of Mexico, through the Sierra Madre Oriental, and across the Tropic of Cancer into northern Nuevo León and Tamaulipas, the northeasternmost states, and nearly to southernmost Texas, USA ( Shear 1973). The projected range spans the breadth of the Middle American isthmus from central Costa Rica to Colima, Mexico, where it angles northeastward and curves to near the Rio Grande. The northernmost locality is Bustamente, Nuevo León, but nearby Sabinas Hidalgo, where Ceuthauxus nuevus (Chamberlin) occurs ( Chamberlin 1942, Loomis 1968, Hoffman 1999, Bueno- Villegas et al. 2004), is closer to the US, being some 77 km (48 mi) from the river above Roma, Starr County (Co.), Texas. Like the aforementioned families, Rhachodesmidae has never been encountered north of the watercourse, so the family differs from Allopocockiidae (Spirobolida) , whose northernmost species, Anelus richardsoni (Pocock) , inhabits Willacy Co., Texas, 99 km (62 mi) north of the river ( Cook 1911; Chamberlin and Hoffman 1958; Hoffman 1980, 1999; Shelley and Hoffman 1995). Discounting the Chisos Mountain species in west Texas (Big Bend National Park, Brewster Co.) and the two in the Appalachians ( Hoffman 1998, 1999; Shelley 1989, 1999), Rhysodesmus Cook ( Polydesmida : Xystodesmidae ) also traverses the River into southernmost Texas, as R. texicolens (Chamberlin) inhabits Webb, Willacy, and Cameron Cos. ( Chamberlin 1938, 1943; Chamberlin and Hoffman 1958; Hoffman 1970, 1980, 1999; Shelley 1987).

Aceratophallus lamellifer Brölemann , the southernmost species, occurs at Chitaria, Cartago Province (Prov.), and Parismina, Limon Prov., Costa Rica ( Chamberlin 1933, Loomis 1968, Hoffman 1999), so we project Rhachodesmidae for the Osa Peninsula to the northwest, where they have never been taken. They do not inhabit Panama ( Hoffman 1999), although Loomis (1961) described A. quadratus and Teinorachis tenuis from “presumably/probably Canal Zone,” and subsequently ( Loomis 1964, 1968) reported “probably Canal Zone” and “probably Panama.” According to Loomis (1971), the millipeds were with material that O. F. Cook collected in 1923 in Haiti; Loomis inquired, since the family is unknown from Hispaniola, and Cook replied that they were probably from the Canal Zone where he had also sampled that year. Because the family was known from neighboring Costa Rica, Loomis (1961) considered Cook’s response reasonable and characterized the species as “likely members of the Panamanian fauna.” Later, he ( Loomis 1971) found A. quadratus in a sample that he had collected at Ameya (misspelled as “Amaya”), Chinandega Dept., Nicaragua (12°34’N, 87°09’W), a railroad stop between Corinto and Chinandega (city). Since they routinely collaborated, Loomis surmised that Cook had taken the specimens from the Ameya sample, examined them, and mistakenly placed them with the Haitian material, so he “corrected” their type localities to Ameya. Twenty-eight years later, Hoffman (1999) compounded the confusion by citing the wrong paper, Loomis (1964) instead of (1971), as the source of the “correction.” Confirmation with fresh material that both A. quadratus and T. tenuis do indeed occur there is desirable.

We believe that insufficient time has passed since Rhachodesmidae originated for it to spread as far southward as Panama. They are known from all countries within the projected range except Belize, which we eliminate below, and Honduras, where records are needed.

BELIZE: Cayo District, Xunantunich Ruins near Guatemala border, M, 7 August 1985, and M, F, 8 August 1990, M. A. Brittain ( NCSM). Toledo District, Blue Creek Cave, M, juv., 20 February 1980, B. Martin ( CMN) New Country Records.

Remarks. According to Causey (1973), the only polydesmidan family that is more abundant in Mexican caves than Rhachodesmidae is Pyrgodesmidae (= Stylodesmidae ).

Figures

Figure 2. Known and projected distribution of Rhachodesmoidea. Red line, Rhachodesmidae; green star, area of Tridontomidae in Alta Verapaz Dept., Guatemala (Loomis and Hoffman 1962, Shear 1977). Red dot, type locality of Tiphallus torreon; blue dot, provisional locality in the Sierra Las Delicias. Blue triangles, rhachodesmid localities in Belize detailed in the text.