Parajulus

Shelley, Rowland M., 2008, Way Down South: The milliped family Parajulidae (Julida: Parajulini) in Mexico and Central America; first records from El Salvador and the Baja California Peninsula, Zootaxa 1893, pp. 1-37 : 14

" Parajulus " rosanus Chamberlin, 1943

Diagnosis. Anterior gonopod coxal processes expanding variably basally, curving caudad apically, subequal in lengths to those of telopodites. Anterior branch of posterior gonopod moderately long, anterior margin variably prolonged; solenomere located caudal to opening of seminal canal, curving distad, variably falcate, spinules present on anterior margin; caudal projection broadly curved, overhanging solenomere and part or all of anterior branch, distal extremity curving gently ventrad or strongly dorsad.

Distribution. Northern Distrito Federal and adjoining periphery of Mexico state.

Remarks. The pg of " P." rosanus is so simple as to enable a complete diagnosis. All three branches vary within this pattern, and as specific names are available for the two variants, I conserve them at the subspecific level. The configuration of the pg caudal projection in rosanus appears different than that depicted by Verhoeff (1926:70, fig. 9), which seems shorter, narrower, and more sharply bent. Consequently, " P." rosanus may not belong with M. dampfi , but I tentatively place it here because of the similarly falcate solenomere that is clearly evident in Verhoeff's drawings.

A valid question arises as to distinguishing specific and subspecific differences when little material is available and further sampling is not feasible in the short-term. An element of subjectivity is inevitable, and my interpretation is based on both anatomy and geography, though some workers deplore employing the latter in even preliminary taxonomic decisions. The level of differentiation between rosanus / gyratus , and subsequently herein pueblanus / zempoalus and schmidti /australis n. subsp., involves the degree of expression of common traits like the breadth of the solenomere and the distal curvature of the caudal projection, rather than the presence of totally different features. While documentation of anatomically intermediate forms, constituting irrefutable proof of intergradation, is desirable and clearly the best evidence of geographic races, such forms are not known to exist for these taxa, and it is not presently possible to travel to Mexico and Guatemala to search for them. Decisions must therefore be based on the available material, and without additional evidence, I interpret the former situation as reflecting subspecies and the latter as evidence of reproductive isolation and hence full species. From my overall experience with millipeds in general and parajulids specifically, I believe that rosanus / gyratus and the other forms mentioned above are not reproductively isolated from each other; they are geographically compatible, and their gonopodal configurations seem too similar to represent distinct species. It is also appropriate to recognize australis taxonomically because it constitutes the southernmost record of the family and order in the hemisphere, and as names are available for the other forms, it is likewise appropriate to conserve them at the subspecific level. Valid argumentations can be advanced for different interpretations, but when field sampling is feasible, I have found that anatomically intermediate forms can be retrieved between ones that are as proximate and similar as these are. In documented cases of subspecies linked by intergrades, they likewise differ by the degree of expression of common features; for example in Sigmoria (Sigmoria) latior (Brölemann, 1900) ( Polydesmida : Xystodesmidae ) ( Shelley 1976, 1981; Shelley & Whitehead 1986), the subspecies differ in the degree of expansion of the medial gonopodal flange, the size and shape of the prefemoral process, the size of the telopodal tooth, and the length of the distal zone. In my experience, when geographically proximate surface-dwelling forms differ in this manner, they probably represent a clinal continuum and hence are more likely to be subspecies than species. I adhere to this observation herein, but as with any taxonomic action, alterations can be effected if future discoveries so dictate. An additional benefit in this particular case is that two available names can be conserved while simultaneously simplifying the nomenclature.