Paraneseuthia disjuncta, Jałoszyński, 2025

Jałoszyński, Paweł, 2025, An unexpected discovery: the first species of Paraneseuthia Franz from the Mascarene Islands (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5646 (1), pp. 124-130 : 125-127

Paraneseuthia disjuncta sp. nov.

( Figs 1–5 )

Type material. Holotype: MAURITIUS: ♂, two labels: “ Maurice / Ile des Aigrettes / 24 XII 74 / Schauenberg ” [white, handwritten]; “ PARANESEUTHIA / disjuncta m. / P. Jałoszyński, 2025 / HOLOTYPUS” [red, printed] ( MHNG).

Diagnosis. Body extremely small (BL <0.7 mm); head, protibia and metaventrite in male unmodified; punctures on head and pronotum inconspicuous, on elytra larger and dense, but shallow and diffuse; setae on head, pronotum and elytra extremely short, inconspicuous; aedeagus in ventral view strongly elongate and asymmetrical, broadest in sub-basal region and with sinuate lateral margins, apical region subtrapezoidal with one hyaline subtriangular distolateral lobe; parameres of different lengths, each with one minute apical seta.

Description. BL 0.68 mm. Body of male ( Fig. 1 ) elongate and moderately convex, moderately light brown with legs and antennae slightly lighter, setae yellowish.

Head broadest across large, strongly convex and coarsely faceted eyes, HL 0.08 mm, HW 0.16 mm; vertex and frons confluent and evenly, weakly convex; supraantennal tubercles small and indistinct. Punctures on head dorsum inconspicuous; setae extremely short, barely discernible. Antennae slender but short, shorter than half BL, with distinctly delimited trimerous clubs, AnL 0.28 mm, antennomeres 1–2 elongate, 3 strongly transverse, 4–7 each about as long as broad, 8 transverse, 9 and 10 each enlarged and transverse, 11 slightly broader than 10, about as long as 9–10 together, about 1.6 times as long as broad.

Pronotum semielliptical, equally broad between base and anterior third (in Fig. 1 slightly tilted anteroventrally, so the shape is not shown in strictly dorsal view). PL 0.20 mm, PW 0.23 mm. Anterior margin rounded, lateral margins rounded in anterior third and straight posteriorly, and posterior margin weakly arcuate with short and shallow emargination in front of scutellum, posterior corners nearly right-angled and blunt; pronotal base with pair of small but distinct inner pits not connected by groove, with outer pair of L-shaped impressions near each hind corner (with the bottom line of ‘L’ directed mesad), and with small and shallow median pit. Punctures on pronotal disc fine and inconspicuous; setae sparse and short, nearly recumbent.

Elytra oval, broadest slightly anterior to middle and evenly rounded laterally, evenly convex; EL 0.40 mm, EW 0.30 mm, EI 1.33; humeral calli distinct but small, basal impressions indistinct; apices separately rounded. Punctures on elytra more distinct than those on head and pronotum, dense but shallow and diffuse; setae short and sparse, nearly recumbent. Hind wings well developed.

Metaventrite unmodified.

Legs moderately long and slender, unmodified.

Aedeagus ( Figs 2–5 ) slender, AeL 0.13 mm; median lobe in ventral view strongly elongate and asymmetrical, broadest in sub-basal region and with sinuate lateral margins, apical region subtrapezoidal with one hyaline subtriangular distolateral lobe; endophallic structures poorly sclerotized; parameres slender, slightly broadened in median region, of different lengths, not reaching apex of median lobe, each with one minute apical seta.

Female. Unknown.

Distribution. Île aux Aigrettes at Mauritius.

Etymology. The adjective disjuncta refers to the terra typica remote from the previously known range of Paraneseuthia .

Remarks. The locality listed on the label as Ile des Aigrettes is in fact Île aux Aigrettes, a small island off the south-east coast of Mauritius (Ile des Aigrettes is an island in Baie du Tonnerre in northernmost Madagascar). Three very similar females from La Réunion (Albion and Saint-Philippe) are also deposited at MHNG. One was studied as a whole-body transparent mount in Canada balsam under compound microscope to confirm the diagnostic characters of Paraneseuthia .

The aedeagus of P. disjuncta is unique and especially the strongly asymmetrical apical region allows for unambiguous identification. Similarly slender aedeagi are typical of two species inhabiting New Guinea, P. rugosa Jałoszyński, 2020 or P. levigata Jałoszyński, 2010 . However, these two species have symmetrical apices. Slender aedeagi with asymmetrical apices can also be found in New Guinean species, P. devia Jałoszyński, 2008 , and P. guineana Jałoszyński, 2009 . The shape of the distal asymmetrical region in these species is clearly different than in P. disjuncta . Externally, P. disjuncta is unremarkable, except for being one of the smallest species of the genus.

Among all nominal species of Paraneseuthia (see distribution in Fig. 6 ), the newly described P. disjuncta surprisingly shows closest morphological similarities to New Guinean congeners. Clearly the distribution of this enigmatic and rarely collected genus is still inadequately known, and the discovery of species on the Indian Ocean islands is certainly not the last biogeographical surprise.

Figures

FIGURE 6. Distribution of nominal species of Paraneseuthia.

FIGURES 1–5. Holotype of Paraneseuthia disjuncta sp. nov. Dorsal habitus (1), aedeagus in ventral (2, 4) and lateral (3, 5) views.