Madegassosorius Scheerpeltz, 1961

Sapieja, Mateusz & Jałoszyński, Paweł, 2024, Taxonomic study on Afrotropical Osoriinae (Coleoptera: Staphylinidae). Status of Mimogonellus Fagel and Madegassosorius Scheerpeltz, Zootaxa 5415 (3), pp. 436-450 : 445-447

Status of Madegassosorius Scheerpeltz, 1961

The type species of Madegassosorius (illustrated in Figs 3 , 5, 7 , 10, 11 , 13 , 26 , 28, 32–34 , 37, 38, 42 , 47–50 , 52 ), closely resembles the type species of Mimogonellus . The following characters found to be different in these species, some treated as diagnostic features for Madegassosorius by previous authors, are discussed below.

Shape of pronotum. The pronotal margins converging posteriorly in Osoriini provide a broad constriction between the prothorax and mesothorax, where the distal portions of profemora fit. Therefore, the shape of the pronotum is important for the mobility of the fore legs. This function is realized either by a rapid posterior narrowing (pronotum subcordiform), or simply by a graduall narrowing (pronotum inversely subtrapezoidal). Most nominal species of Mimogonellus have the pronotum subcordiform, so that the lateral margins are distinctly concave near base, as those in Mm. leleupi ( Figs 1–2 ). The type species of Madegassosorius , Md. keiseri , has the pronotum inversely subtrapezoidal, with lateral margins barely noticeably sinuate. However, the pronotal shape is variable within both genera. For instance, in Md. robustus Coiffait and Md. sogai Coiffait , the pronota are intermediate in shape between the one in Mm. leleupi and Md. keiseri , with the basal region distinctly narrowed, but less rapidly and more shallowly than in Mm. leleupi . The variable shapes of pronota within Madegassosorius , from gradually narrowing from anterior third, to abruptly narrowed in the posterior fourth, were illustrated by Coiffait (1979: figs 3–4). The convex vs. strongly sinuate lateral pronotal margins seem to be extreme states of a morphocline and this character cannot be used to unambiguously place species in Mimogonellus or Madegassosorius .

Lateral pronotal carinae. Coiffait (1979) used the carina to distinguish Mimogonellus (carinae incomplete, posteriorly obliterated because of the posterior abrupt narrowing) from Madegassosorius (carina complete, reaching posterior pronotal corners). In fact, the lateral pronotal margins in Mm. leleupi are somewhat diffuse on entire length, not forming sharp edges, in a cross-section they are rounded, not sharp-angled. In. Md. keiseri , the hypomera are more impressed, so that the lateral pronotal margins are slightly more distinct, and the pronotal base bears a pair of shallow lateral impressions that compress the pronotal margins near the base, forming distinct lateral carinae. However, the carinae do not correlate with the presence of the posterior abrupt narrowing, nor with the presence of the lateral antebasal impressions. For instance, in Mm. leleupi the lateral pronotal margins form indistinct lateral edges in front of the posterior narrowing, and within the narrowed region there are no traces of lateral edges. In Mm. microphthalmus Fagel ( Rwanda), with the pronotum similarly subcordiform as that in Mm. leleupi , the lateral pronotal margins in front of the posterior narrowing are also poorly marked, but within the narrowed region slightly diffuse edges can be seen. Such edges, in turn, are not present in Mm. collarti Fagel ( DR Congo), which has conspicuous antebasal lateral impressions on the pronotum. Thus, the length of the lateral pronotal carinae is also a weak taxonomic character and cannot be used to define Madegassosorius .

Antebasal pronotal impressions. Fagel (1955) defined Mimogonellus as not having lateral impressions on the pronotal base. The type species of Madegassosorius has such impressions, while most species of Mimogonellus are indeed devoid of such structures. However, Fagel himself placed in Mimogonellus Mm. collarti , which has two pairs of distinct antebasal impressions.

Adsutural stria/sulcus on the elytra. Coiffait (1979) mentions that Madegassosorius is characterized by the lack of the adsutural sulcus on each elytron, in contrast to Mimogonellus , which has such a structure. This sulcus demarcates a narrow elevated sutural area and is clearly present in the type species of both Mimogonellus and Madegassosorius ( Figs 27‒28 ).

Male sexual characters. The difference in the structure of the abdominal sternite VIII in the examined male specimens is evident ( Fig. 35 vs 37). However, based on many examined nominal species of Mimogonellus , it can be concluded that the size, shape, placement and number of lateral teeth or denticles on the sternite is highly variable. In Mm. leleupi , the sternite VIII ( Fig. 35 ) has only tiny lateral denticles, while in Mm. microphthalmus , Mm. africanus Bernhauer and Mm. similis Fagel there are 6–7 pairs of teeth, not only on margins, but also on the dorsal surface. Moreover, the shape of the sternite VIII within Mimogonellus is variable, from subtriangular to subtrapezoidal with a truncate apex and concave posterior margin (e.g., in Mm. similis ). Therefore, this structure and its modifications cannot be used to distinguish these genera.

As a result, we conclude that the observed differences between the type species of Mimogonellus and that of Madegassosorius reflect species-level variability within one genus. Therefore, Madegassosorius Scheerpeltz , syn. n. is placed as a junior synonym of Mimogonellus Fagel. The resulting new combinations are as follows:

Figures

FIGURES 1–3. Dorsal habitus of Mimogonellus leleupi (Cameron), lectotype male (1) and paralectotype female (2); Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (3).

FIGURES 4–7. Mimogonellus leleupi (Cameron), lectotype male (4, 6); and Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (5, 7). Head and pronotum in dorsal view (4, 5), right antenna in dorsal view (6, 7).

FIGURES 8–11. Mimogonellus leleupi (Cameron), lectotype male (8, 9) and Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (10, 11). Head (8, 10) and prothorax (9, 11) in ventral view.Abbreviations:bst, basisternal region of prosternum; ce, compound eyes; cx1, procoxa; fm1, profemur; fnss, ‘false notosternal suture’; hr, hypostomal ridge; hy, hypomeron; pc, pronotal carina; pcf, procoxal fissure; pstp, prosternal process; sm, submentum; tn, trochantin; tr1, protrochanter;?hs, presumably fused hypostomal sutures. Arrowheads indicate profemoral denticles.

FIGURES 12–13. Mimogonellus leleupi (Cameron), lectotype male (12) and Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (13); mouthparts in ventral view.Abbreviations: bst, basistipes; cd, cardo; lg, ligula; lp1–3, labial palpomere 1–3; md, mandible; mn, mentum; mxp1–4, maxillary palpomere 1–4; ppf, palpifer; sm, submentum.

FIGURES 25–26. Mimogonellus leleupi (Cameron), lectotype male (25) and Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (26). Pterothorax in ventral view. Abbreviations: aest3, metanepisternum; amtvp, anterior metaventral process; el, elytra; epm3, metepimeron; msvp, mesoventral intermesocoxal process; mtvp, metaventral intermetacoxal process; pcr, procoxal rest; pp, prepectus; v2–3, ventrite 2–3.

FIGURES 27–34. Mimogonellus leleupi (Cameron), lectotype male (27, 29, 30, 31) and Mimogonellus keiseri (Scheerpeltz), comb. n. paratype male (28, 32, 33, 34). Elytra in dorsal view (27, 28); protibia (29, 32), mesotibia (30, 33), and metatibia (31, 34) in ventral vies. Abbreviations: mss, mesoscutellar shield. Arrowheads indicate adsutural sulcus.

FIGURES 35–42. Mimogonellus leleupi (Cameron), lectotype male (35, 36, 41), Mm. leleupi (Cameron), paralectotype female (39, 40), and Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (37, 38, 42). Male sternite VIII (35, 37); male tergite VIII, IX and X (36, 38); female tergite IX and X (39); female sternite VIII (40); distal portion of abdomen in right lateral view, upside down (41, 42). Abbreviations: s, sternite; t, tergite.

FIGURES 43–50. Mimogonellus leleupi (Cameron), lectotype male (43–46), and Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (47–50). Aedeagus in ventral (43, 45, 47, 49) and lateral (44, 46, 48, 50) views.

FIGURES 51–53. Original labels of Mimogonellus leleupi (Cameron), lectotype male (51), and Mimogonellus keiseri (Scheerpeltz), comb. n., paratype male (52); Mimogonellus keiseri (Scheerpeltz), comb. n., holotype male and its labels (53) (photo: Matthias Borer).