Benlomondia Shear & Marek, 2025

Shear, William A. & Marek, Paul E., 2025, Additions to the family Caseyidae Verhoeff, 1909. V. The new genus Benlomondia and two new species (Diplopoda, Chordeumatida, Striariidea, Caseyoidea), Zootaxa 5659 (3), pp. 400-406 : 401-402

Benlomondia Shear & Marek , new genus

Type species Benlomondia benlomondensis Shear & Marek , new species

Diagnosis. The minute size of its species (ca 5 mm) separates Benlomondia from other Caseyidae , which are larger than 8 mm in length, except for Martenseya minutocaeca Shear, 2021 , but that species is eyeless while Benlomondia species have black, pigmented ommatidia. From members of the subfamily Ochrogrammatinae , Benlomondia is distinct in lacking broad lamellae projecting from the male mandibular stipes, and from species of Caseya Cook & Collins, 1895 , in the male seventh coxae without modifications or processes. The status of the genus Speoseya Causey, 1963 , is presently unclear, but that single species is twice the size of either of the two species of Benlomondia . Additionally, the new genus is distinct from the related genus Opiona Chamberlin, 1952 , in several characters of the gonopods. In Benlomondia the sterna, coxae and angiocoxites of the gonopods are fused into single units on each side, and the angiocoxites, while separated left from right, are so tightly appressed in the midline that they are functionally one structure. While some species of Opiona have the distal elements of the gonopods arising from a coxosternum, in no case are these distal elements also part of the gonopod complex, and no species are known in which the angiocoxites are closely appressed. Benlomondia species gonopods also lack flagellocoxites, present in nearly all Opiona species, nor have vestigial articulated telopodites, a feature of more than half the species of Opiona . The ninth legs of Benlomondia have reduced telopodites which are laterally flattened, unlike the inflated button-shaped telopodites of Opiona species. The long coxal lobes, strongly reduced and modified telopodites of the third male legs characteristic of species of Opiona , are not seen in Benlomondia .

Etymology. The name of the new genus is feminine in gender and refers to the community of Ben Lomond, California, type locality of the type species.

Description. Tiny caseyid millipedes (<5 mm long) with 30 postcephalic rings. Trunk tapering evenly anteriorly and posteriorly. Rings without shoulders or paranota, smooth and shining. Unpigmented except for faint grayish mottling on anterior end of some individuals. Head ( Fig. 1 ) with three or four black ommatidia on each side. Metazonites with few faint ventrolateral striae. Segmental setae in a straight posterior row, acute. Male mandibles not modified. First legpair of males incrassate, with one or two swordlike, slightly twisted macrosetae on femora and postfemora; tarsus with ventral comb of modified setae ( Fig. 2 ). Second legpair of males reduced, coxae with short, curved gonapophyses densely set with long, curled setae ( Figs 2, 3 ). Coxae of third legpair of males with short distal lobes, densely set with recumbent, curved setae and single long, acute terminal seta; telopodites slightly reduced, prefemora not enlarged and flattened ( Figs 4 , 10 ). Legpairs four to seven unmodified, hardly enlarged. Gonopod complex ( Figs 5, 6 , 9 ) consisting of sternum, coxa and angiocoxite fused on each side with angiocoxites tightly appressed to each other in midline; distally angiocoxites with complex branches and fine, unsocketed cuticular filaments posteriorly. Colpocoxites elongate, poorly sclerotized. Ninth legpair ( Figs 7, 9 ) with telopodites and coxal processes roughly equal in size, coxal processes broad, curved, with pore at the base. Telopodites of a single podomere, laterally flattened, setose. Tenth legpair with enlarged coxae having anteriorly opening glands, coxae without posteriorly directed processes.

Notes. While the pregonopodal leg modifications of the two species of Benlomondia resemble those of species of Opiona , they are much less obvious. The gonapophyses of the male second legs are shorter than the femora; the telopodites of almost normal size, with the typical five postcoxal podomeres. The male third legs of Opiona species have very elongate projecting coxal lobes, with a strongly reduced telopodite attached about in the midlength of the lobes or even more distally. The femora of the third leg telopodites are typically expanded and flattened. Benlomondia species do not have such elongate coxal lobes and the attachment of an unreduced telopodite is more basal; the telopodite femora are cylindrical, not expanded or flattened. The tenth legpair coxae of Opiona species have hooked processes, which are absent in Benlomondia species. The lesser modifications seen in Benlomondia species may be associated with the unusually small size of the animals.

Figures

FIGURES 1–6. Benlomondia benlomondensis, sp. nov., paratypes. 1. Head and anterior end of female, lateral view. 2. Legpairs 1 and 2 of male, anterior view. 3. Gonapophyses. 4. Left leg 3 of male, posterior view. 5. Goonopods, anterior view. 6. Gonopods, posterior view. Abbreviations: ac, angiocoxites; cc, colpocoxite; cl, coxal lobe; cx3, coxa of leg 3; cxs, coxosternite of gonopods; ga, gonapophysis; t1, telopodite of leg 1; t2, telopodite of leg 2; t3, telopodite of leg 3.

FIGURES 7–10. 7, 8. Benlomondia benlomondensis, sp. nov., paratype male. 7. Legpair 9, posterior view. 8. Right legpair 10, anterior view. 9, 10. Benlomondia mateo, sp. nov., male holotype. 9. Gonopods and legpair 9, posterior view. 10. Legpair 3, anterior view. Abbreviations: ac, angiocoxite; cc, colpocoxite; cl, coxal lobe of leg 3; cp, coxal process; cx3, coxa of leg 3; cx9, coxa of leg 9; cx10, coxa of leg 10; g, gland opening; t3, telopodite of leg 3; t9, telopodite of leg 9; t10, telopodite of leg 10.