Paropiona Shear & Marek 2025, new genus
Creators: name: Shear, William A.
name: Marek, Paul E.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Diplopoda
Chordeumatida
Caseyidae
Paropiona

description: Paropiona Shear & Marek, new genus
Type species Paropiona gardneri Shear & Marek, new species.
Diagnosis. Species of this genus are unique among caseyids in entirely lacking gonopod colpocoxites. Differing from Vasingtona Chamberlin, 1941 and Ochrogramma Gardner & Shelley, 1989 in lacking the ventral lamina of the mandible in males seen in those genera. From Caseya Cook & Collins, 1895, the new genus differs in not having the coxae of the seventh legpair of the male greatly enlarged and with complex processes. In species of Opiona Chamberlin, 1951, the gonopods have colpocoxites and flagellocoxites; these are absent in species of Paropiona gen. nov. In addition, the reduced telopodites of the male ninth legs of Opiona species are rounded and button-like, while in species of Paropiona they are narrow and sinuously curved. From Opionoides gen. nov., Paropiona species differ in lacking gonopod flagellocoxites (possibly vestigial in one species); Opionoides gonopods have both flagellocoxites and colpocoxites and have a crown of thorny processes on the anterior angiocoxites. The posterior angiocoxites are densely fimbriate on their mesal surfaces in Opionoides; these features are not found in Paropiona species. The ninth leg telopodites of Opionoides cataracta, sp. nov., are like those of Opiona species.
Etymology. The name of the new genus is feminine in gender and conveys its relationship to the genus Opiona.
Description. Caseyid millipedes with 30 rings, about 8–12 mm long (Figs 30, 31)
Mandibles of males not modified.
Male first legpair (Fig. 1) somewhat reduced, with few elongate, flattened, spiral setae on postfemur and tibia; tarsi with sparse ventral tarsal comb.
Male second legpair (Figs 2, 13) with long coxal gonapophyses slightly curved, subequal in length to reduced telopodites; telopodite femora long, more distal podomeres much shortened. Gonapophyses with opening of vas deferens at base, more distal accessory pore present.
Male third legpair (Figs 3, 13) with prominent, flattened, rounded coxal lobes tightly appressed in midline, lacking apical tuft of modified setae. Telopodites attached midway distal on coxae, with four podomeres; prefemora not flattened or enlarged.
Male legpairs four to seven slightly encrassate, otherwise unmodified.
Gonopods (Figs 4–7, 14–16) with coxae and sternum fused without midline suture.Anterior angiocoxites slightly inclined posteriorly, simple, erect or sinuously curved. Posterior angiocoxites present or absent. Flagellocoxite absent or possibly vestigial in P. gardneri sp. nov. Gonopod telopodites large, robust, erect and divergent or passing anteriorly between angiocoxites. Colpocoxites absent.
Male legpair nine (Figs 8–10, 17–20) with elongate coxae bearing divided coxal process, the mesal branch thin and appressed to telopodite. Coxal pore present at base of coxal process. Telopodite single podomere, narrow, elongate, with apical tuft of stout setae directed mesally.
Male legpair 10 (Figs 11, 12, 21) with enlarged coxae bearing large, frequently everted glands and hooked coxal process; trochanters with small, distal, bifid process; prefemora and femora with a ventral row of acute denticles.
Notes. The modifications of the pregonopodal legs of the males in the two species of Paropiona are very similar to those found in species of Opiona. However, we noted a feature of the gonapophyses of the second legs that has not been seen before in any caseyids: an accessory pore distal to the opening of the vas deferens, which is situated at the base of the gonapophysis. An examination of a few species of Opiona confirms that at least in those species, this pore also occurs. This accessory pore is not present in species of the subfamily Ochrogrammatinae (Shear & Marek 2024) nor in species of Caseya. The gonopods of the two species of Paropiona differ strongly from those of Opiona species in lacking colpocoxites, arising from a coxosternum and lacking flagellocoxites (a single vestigial flagellocoxite may be present in P. gardneri sp. nov.), which are numerous in those species, and often complexly sheathed by the posterior angiocoxites. Paropiona gonopods are in fact so different from those of any other caseyids that establishing even tentative homologies among them is difficult. The gonopods proper arise from a coxosternite and consist of two divisions: anterior and posterior. The anterior division is angiocoxal and in Paropiona gardneri sp. nov., consist of anterior and posterior angiocoxites, while in Paropiona aenigma sp. nov., there is only a single angiocoxite. While functional flagellocoxites appear to be absent in both species of the genus, a small vestigial branch arising from the posterior surface of the anterior angiocoxite in P. gardneri gonopods may be flagellocoxal. In P. aenigma sp. nov., the posterior angiocoxites and any trace of flagellocoxites are apparently absent. We are referring to the posterior divisions of the gonopods as telopodites because they appear to arise from sockets in the coxosterna. It is possible that these structures could also be heavily sclerotized homologs of what we have called the colpocoxites in other caseyids. However, caseyid colpocoxites are very lightly sclerotized and amorphous in shape. If our interpretation is correct, colpocoxites are absent in species of Paropiona. Telopodites are uncommon as a component of the gonopods of most of the families of Chordeumatida, the functional gonopod divisions developing primarily from the coxae. The ninth legs of the males of Paropiona species are reduced to the coxae and single telopodite podomeres, as is typical of caseyids; however, instead of being rounded, globular and button-like, they are elongate and curved, with tufts of stout, ensiform setae in a mesal group at their tips. The coxal processes are bifid, as in many Opiona species, but the lateral branch is small, thin, and usually closely appressed to the telopodite so that its presence is sometimes obvious only in SEM images. The mesal branch is much more robust, sinuously curved and as long or slightly longer than the telopodite. At the base of this mesal branch is a small pore; we have also observed such a pore in species of Ochrogramma (Shear & Marek 2024) and think this pore is homologous to the much larger pores of the tenth coxae, where spermatophores are formed.
While the majority of collections of both species of Paropiona gen. nov., were collected from November to March, as expected for winter-active chordeumatidan millipedes, some were taken as early as September and as late as June, indicating perhaps a longer period of activity than in other chordeumatidans in the region.
description: Published as part of Shear, William A. & Marek, Paul E., 2025, Additions to the millipede family Caseyidae Verhoeff, 1909. IV. Two new genera and three new species (Chordeumatida, Striarioidea, Caseyidae), pp. 533-547 in Zootaxa 5631 (3) on pages 534-536, DOI: 10.11646/zootaxa.5631.3.7, http://zenodo.org/record/15371308