Paederus Fabricius, 1775

Shaw, Josh Jenkins, Gehler, Alexander & Kaulfuss, Uwe, 2024, Review of the rove beetles (Coleoptera: Staphylinidae) from the Pliocene of Willershausen, Germany, Zootaxa 5424 (1), pp. 116-126 : 121-122

Genus Paederus Fabricius, 1775

† Pliosyntomium Korge, 1967 syn. nov. (Type species: Pliosyntomium schmidti Korge, 1967 by original designation).

† Paederus schmidti ( Korge, 1967) comb. nov.

Material. Holotype, GZG.W.35142 (597-1) ( Fig. 4 ).

Remarks. According to Newton (2022), † Pliosyntomium Korge, 1967 is currently unassigned to a tribe within the subfamily Oxytelinae . Cai et al. (2016) listed † Pliosyntomium in the tribe Syntomiini , albeit without explanation but presumably based on the original description of Korge (1967) who noted its affinity with Syntomium , among other genera of Oxytelinae .

Among other characters, Korge (1967) mentions: “Die Unterfamilie der Oxytelinae zeichnet sich u. a. dadurch von allen anderen Subfamilien der Staphylinidae aus, dass vom zweiten Abdominalsegment Tergit und Sternit ganz deutlich ausgebildet sind. Bei den anderen Unterfamilien sind von den ersten beiden Segmenten nur die Tergite vorhanden, aber nicht chitinisiert und unter den Flügeldecken verborgen; die Sternite sind ganz reduziert.” [The subfamily of the Oxytelinae is characterized i.a. from all other subfamilies of the Staphylinidae in that the tergite and sternite are clearly developed from the second abdominal segment. In the other subfamilies, only the tergites are present from the first two segments, but are not chitinized and are hidden under the wing covers; the sternites are quite reduced.]

Korge (1967) was not entirely wrong in that a synapomorphy of Oxytelinae is the presence of the second sternite of the abdomen. However, Korge’s (1967) interpretation of the fossil was incorrect. No sternites are visible at all on the specimen, but one can clearly observe the fused tergites I and II which are exposed and visible due to the dislocation of the right elytron ( Fig. 4 , T 1 , T 2 ). The left elytron is in resting position, covering the left portion of tergites I and II. If the right elytron was also in resting position, tergites I and II would be completely covered.

Based on overall body shape and above-mentioned characters, all subfamilies of Staphylinidae can be excluded except Aleocharinae , Paederinae and Staphylininae . Unambiguous characters that would allow assignment of the fossil to any of these subfamilies are unfortunately not preserved. The relatively large size of the fossil (ca. 6 mm in length) is more typical of Paederinae and Staphylininae . The elongate body, pronotum apparently differently colored to the elytra, bicolored front leg and abdomen, and abdomen widest at tergite VII immediately suggest affinities of this taxon to the genus Paederus . Very few rove beetles have such aposematic coloration, which is widespread in the genus Paederus (e.g. Parker 2017). Some species of Oedichirus Erichson, 1839 ( Paederinae : Pinophilini : Procirrina ) are also aposematically colored but placement in this genus can be excluded based on the presence of paratergites on the abdomen (lacking in all members of the subtribe Procirrina ). Aposematically colored Staphylininae are much less frequent and in general Staphylininae have the abdomen widest at tergite III or IV. Although we cannot rule out distortion of the specimen during preservation, based on all above-mentioned characters and considerations, the originally proposed affinity of † Pliosyntomium to the subfamily Oxytelinae and the genus Syntomium is not supported. † Pliosyntomium Korge, 1967 syn. nov. is here proposed as a junior synonym of Paederus Fabricius, 1775 . This generic synonymy necessitates transfer of the species to the respective genus resulting in the tentative new combination Paederus schmidti ( Korge, 1967) comb. nov.. † Paederus schmidti represents the second fossil species of the genus, the other being Paederus adumbratus Wickham from the late Eocene Florissant Formation (Colorado, USA) ( Wickham 1913). Extant species of Paederus in Europe are often associated with wet habitats, moors, wet meadows, river and stream edges and marshes.

Figures

FIGURE 1. GZG.W.18268 (Aleocharinae?). Scale bar = 1 mm.

FIGURE 2. Micropeplus macrofulvus Gersdorf, 1976 (Holotype, GZG.W.24110a+b (30166)). A, Part. B, Counterpart. Scale bar = 1 mm.

FIGURE 4. Paederus schmidti (Korge, 1967) comb. nov. (Holotype, GZG.W.35142 (597-1)), tergites: T1, T2. Scale bar = 1 mm.