Bifurcatella, Shear & Richart & Wong, 2020

Shear, William A., Richart, Casey H. & Wong, Victoria L., 2020, The millipede family Conotylidae in northwestern North America, with a complete bibliography of the family (Diplopoda, Chordeumatida, Heterochordeumatidea, Conotyloidea), Zootaxa 4753 (1), pp. 1-78 : 53

Bifurcatella , new genus

Type species: Bollmanella bifurcata Shear, 1974

Diagnosis: This genus is distinguished from other conotylines by two features of the gonopods in combination. The anterior gonopods are composed of two branches which occupy lateral and mesal positions. Except for one species, the lateral branch is the longest and usually has a more or less complicated tip, while the mesal branch may be short, of medium length, or long and is always simple. The posterior gonopod coxites carry a flagellar or pseudoflagellar basal branch, which, unlike other genera, arises laterally on the coxite, is strongly sinuous and more or less fimbriate towards its tip.

Etymology: The genus name is derived from the species epithet of the type species, referring to the anterior gonopods.

Notes: Besides the type, Bifurcatella unca ( Shear, 1974) , new combination, and the following new species. With regard to the form of the gonopods, the species of this genus conform well to a common pattern. The anterior gonopods are upright, with mesal and lateral branches. The lateral branch (L, Fig. 206 ) may be considered the main body of the gonopod and is either acute, flared or branched at its tip. The mesal branch (M, Fig. 206 ) ranges from only about a sixth the length of the lateral to longer than the lateral and is always simple and cylindrical. The posterior gonopod coxites have a characteristic flagellar or pseudoflagellar (we are not sure if it is movable or not) process (pf, Fig. 207 ) that arises basolaterally and curves around the posterior side of the coxite, describing various curves. This process is robust at its base but tapers to a very fine point and is often fimbriate over at least part of its distal surface. The pseudoflagellar process is usually enclosed in a fimbriate sheath (sh, Fig. 205, 207 ). On the mesal side of the coxite about midway in its length a fimbriate process (fp, Fig. 207 ) is seen, which subtends a pore. The main body of the coxite is decurved near its tip and divided into two or three processes. The modifications of the male pregonopodal legs are various.

We cannot be sure that the big pseudoflagellar branch of the posterior gonopod coxites of Bifurcatella is homologous to the T-shaped branch found in nearly the same position in Taiyutyla , but it is tempting to think so, and to infer that the two genera may share a common ancestral form. Further evidence lies in the resemblance of the T-shaped branch of T. napa to the pseudoflagellar branch in Bifurcatella species.

New records of a previously described species

Figures

FIGS. 204–207. Bifurcatella spp. Figs. 204, 205. Bifurcatella bifurcata. Fig. 204. Right anterior gonopod, posterior view. Fig. 205. Right posterior gonopod coxite, posterior view. Figs. 206, 207. Bifurcatella olympiana. Fig. 206. Anterior gonopods, posterior view. Fig. 207. Left posterior gonopod coxite, posterior view.