Psammodesmus Cook, 1895 Ernostyx Chamberlin, 1941 E. dasys Chamberlin Psammodesmus A new Colombian species in the milliped genus Psammodesmus, symbiotic host for bryophytes (Polydesmida: Platyrhacidae) Hoffman, Richard L. Martinez, Daniela D, Eduardo Florez Zootaxa 2011 3015 52 60 7PVZY Cook, 1895 Cook 1895 [238,578,359,385] Diplopoda Platyrhacidae Psammodesmus Animalia Polydesmida 1 53 Arthropoda genus    PsammodesmusCook, 1895, Brandtia 12: 52. Monobasic with a new species. Typespecies: P. c o sCook, by original designation. — Silvestri, 1897, Boll. Mus. Torino, 12(305): 15. — Hoffman, 1953, Journ. Washington Acad. Sci. 43: 301.— Hoffman, 1980, Classification of the Diplopoda, p. 163. —Hoffman, 1999, Va. Mus. Nat. Hist. Spec. Publ. 9: 398.   Ernostyx Chamberlin, 1941, Bull. American Mus,. Nat. Hist., 78: 497. Monobasic with a new species. Typespecies:  E. dasysChamberlin, by original designation. Synonymized with  Psammodesmusby Hoffman, 1953.   Diagnosis.Terminal lamina of gonopod directed either distad or ventromesad (away from the coxa), solenomere in either case directed sinuously ventrad, in contrast to other Neotropical genera in which both of the apical elements are curved or bent dorsad, thus in the same axis as the coxa.   Comments.The identification of this genus has been solely by circumstantial evidence. The typespecies was based on a female specimen never seen since Cook’s day: not in any likely despository, and presumably lost/misplaced. The original description, which could apply to any number of platyrhacids, is as follows: “ Carinaeof moderate width, with a prominent, square shoulder at base in front; dorsum densely beset with distinct, prominent, rounded granules and divided into three transverse rows of polygonal areas, each of which has a distinct, though not conspicuous tubercle in the middle; tubercles of the posterior row much more conspicuous than the others; first segment with an anterior row of large tubercles, behind which is a distinct transverse depression; vertex densely and finely granular, prominent and cristate on each side of the sulcus; pores removed from the margin by five or six times the diameter of the small ring; clypeus smooth and shining below: Genus Psammodesmus nov., type  Ps. cos, sp. n., Colombia, Philadelphia Academy.” Shortly after publication of this account, F. Silvestri described two new platyrhacids from Ecuador,  Psammodesmus camerani(1897)from Gualaquiza and  P. fasciolatus(1898)from the Rio Peripa, both collected by the renowned Italian ornithologist Enrico Festa. It is not obvious how Silvestri deduced that these species were congeneric with Cook’s rather ambiguously described typespecies. His confidence was not shared by the next writer on these millipeds, H. W. Brolemann (1919)who in reporting specimens from western Ecuadorthat he identified as  fasciolatus, referred the species to  Platyrrhacus[ sic] rather than  Psammodesmus. In this disregard of the Cookian genus, Brolemann was followed by Attems (1938)who placed both  fasciolatusand  cameraniin the subgenus  Tirodesmusof his comprehensive genus  Platyrhacus. Hoffman (1953)on the other hand ventured to recognize  Psammodesmuson the basis of a new species from Panama, and in 1960 went so far as to establish the new tribe Psammodesminifor this one genus, also recognized in the 1980 “Classification”. The discovery that two platyrhacid species quite distinctive in peripheral characters can share a basically identical gonopod structure imposes an important caveat on future use of illustrations of these appendages in definition or identification of species of platyrhacids. Attention to peripheral characters is now mandated, but even a meticulous description like that of Brolemann (1919)for  P. fasciolatuscannot anticipate every detail that future knowledge may require. A precedent to this situation is established in some Nearctic genera of the xystodesmid tribe Rhysodesmini, and the oxydesmid genus  Coromusin particular provides a comparable example.