Unicornella Jaschhof & Sikora, 2020

Sikora, Tomáš, Jaschhof, Mathias & Kurina, Olavi, 2020, Additions to the Estonian fauna of mycophagous Cecidomyiidae (Diptera), with a description of Unicornella estonensis gen. et sp. nov., Zootaxa 4851 (2), pp. 349-363 : 360-361

Unicornella Jaschhof & Sikora gen. nov.

Type species, Unicornella estonensis Jaschhof & Sikora sp. nov., described below.

This new genus is introduced here for a new species of Porricondylini from Estonia, described below as Unicornella estonensis (but see below). The species is represented in our material only by two males, meaning female characters of Unicornella remain unknown for the time being.

Diagnosis. Unicornella comprises small, delicate Porricondylini with basitarsal spines ( Fig. 3D ) and 10 male flagellomeres, characters placing it in group Bb by Jaschhof & Jaschhof (2013: 166). The morphology of males is partially atrophied, recognizable by the small size of the body, the eye bridge lacking dorsal ommatidia, and the wings lacking both branches of the media ( Fig. 3B ). Cryptoneurus Mamaev , another genus of group Bb and largely similar to Unicornella , differs in having 11 male flagellomeres. Unicornella is unique among Porricondylini , both within and outside group Bb, in the structure of the male genitalia ( Fig. 3A ), as follows. The gonocoxal synsclerite has only one process medioposteriorly (as opposed to two or no processes in other Porricondylini ), which is moderately sized and sclerotized; the gonostylus is bilobed, the ventral lobe bearing a toothed, basomedial process and the dorsal lobe bearing normal setae; the parameres are present as small sclerotized tusks whose apices are bent ventrad, and whose bases are apparently linked with each other and with the ventral gonocoxal wall; and the aedeagal apodeme has an angular extension of considerable size apically.

Other male characters. Head. Postcranial setae sparse. Postfrons non-setose. Scape slightly larger than pedicel, both slightly lighter than flagellum. Circumfila sinuous, present on all flagellomeres; neck of fourth flagellomere longer than node ( Fig. 3C ). Palpus slightly shorter than head height, 4 setose, subcylindrical segments, apical segment longest of all. Thorax. Scutum with brown stripes dorsally and dorsolaterally; setae sparse. Pronotum and anepisternum non-setose; anepimeron with 3–4 setae. Wing ( Fig. 3B ). Length/width ratio 2.9. Membrane fully setose. Costal cell narrow, slightly reinforced. Radial cell conspicuously large. Costal break distinct. Rs oblique, indistinct. CuA short, running close to posterior wing edge. Legs densely covered with pointed scales. Foreleg: femur and tibia about same length, tibia longer than T 2. Acropod: claws slightly bent, 1 large tooth basally; empodia one third as long as claws. Abdomen. Sclerites faintly contrasting with surrounding membrane, sparsely setose. Pleural membrane setose. Genitalia ( Fig. 3A ). Ninth tergite (not illustrated) short, subtrapezoid, poorly sclerotized, 2–3 setae at posterior edge. Gonocoxal synsclerite with long setae; a pair of setose protuberances near gonostylar bases; medial bridges not bulging towards aedeagus; ventroposterior portions subtriangular, slightly projecting beyond dorsoposterior portions; dorsal apodemes conspicuously broad. Gonostylus with moderately long setae; basolateral apophysis small. Aedeagal apodeme slightly shorter than gonocoxae; rod-shaped portion thin, slightly longer than apical extension. Hypoproct (not illustrated) markedly smaller than cerci, bilobed apically, lobes rounded, each with 1 apical seta. Cerci (not illustrated) bilobed apically, lobes blunt-ended, each with 2–3 apical setae.

Etymology. The name is derived from the Latin word for unicorn, with unus meaning one and cornu meaning horn, in reference to the single gonocoxal process found in this genus. The suffix - ella is a diminutive and refers to Dallaiella, a genus supposed to be closely related. The name’s gender is feminine.

Phylogeny. Characters of the wing, male antenna and genitalia suggest that Unicornella is most closely related to Coccopsilis Harris, Cryptoneurus (both with basitarsal spines), and Dallaiella Mamaev (without basitarsal spines). All these genera have fewer than 14 male flagellomeres, the wing venation is reduced to only three longitudinal veins (R 1, R 5, and CuA), the gonocoxal synsclerite is clearly broader than long, and the gonocoxal emargination is wide and shallow. Among those genera, Unicornella resembles, on the one hand, Cryptoneurus in that the posterior portion of the gonostylus is strongly enlarged (extended in Unicornella , inflated in Cryptoneurus) and, on the other hand, Dallaiella in that the parameres are tusk-shaped. We deem it possible that these four genera are a monophyletic subgroup of the Porricondylini (including Holoneurini , see Jaschhof & Jaschhof (2013: 164)).

Figures

FIGURE 3: Morphology of Unicornella estonensis, male, holotype. A: Genitalia, ventral. B: Wing, dorsal, setae omitted. C: Fourth flagellomere, lateral. D: Basitarsus of foreleg, lateral. Scales for A, C, D, 0.05 mm; for B, 0.5 mm.