Cypha sp.

Yamamoto, Shûhei & Newton, Alfred F., 2024, The First Aleocharine Rove Beetle Fossil from Mid-Eocene Bitterfeld Amber of Germany (Coleoptera: Staphylinidae: Aleocharinae: Hypocyphtini), The Coleopterists Bulletin 78 (2), pp. 233-238 : 234-236

Cypha sp.

( Figs. 1 , 2 )

Material Examined. 1 ex., sex unknown; deposited in HUM, accession no. SEHU-0000121233 .

The beetle fossil is embedded in a small, flattenedrhombus, yellowish transparent amber piece (12.5 × 10.9 × 3.3 mm).Although the staphylinid is well preserved and fully visible from both the dorsal and ventral views, its ventral side is partially poorly visible due to a large air bubble, preventing detailed observation of the abdomen.

Locality and Horizon. Bitterfeld, Saxony-Anhalt, eastern Germany; middle Eocene (Wolfe et al. 2016).

Description. Body small, broadly droplet shaped, dorsoventrally rather convex, 0.92 mm long in situ (from apex of pronotum to apex of abdomen). Color uniformly blackish brown to dark reddish brown; mouthparts, legs, and abdominal terminalia somewhat paler. Surface densely pubescent with fine, short setae on pronotum, elytra, and abdomen; antennae with both short and long setae.

Head ( Figs. 1B , 2A ) hypognathous, deflexed, very strongly transverse, 2.14 times wider than long, 0.14 mm long, 0.30 mm wide (including eyes). Clypeus wide, broadly rounded at anterior margin. Compound eyes ( Figs. 2A, B ) moderately large, weakly laterally protuberant, coarsely faceted. Antennal insertions ( Fig. 2A ) fully exposed, located on vertex between eyes.Antenna ( Figs. 2A–C ) short, with 10 antennomeres, with last three antennomeres forming a very loose club, with left antenna 0.36 mm in length; antennomere 10 very long, nearly as long as three preceding antennomeres combined.Mandibles inconspicuous. Maxillary palpi ( Figs. 2B–D ) 4-segmented, short, with conical terminal palpomere. Labial palpi ( Fig. 2A ) 3-segmented, with long, acicu- late terminal palpomere.

Pronotum ( Fig. 1A ) broadly transverse, semicir- cular, strongly convex dorsally, widest at base, 0.18 mm long, 0.48 mm wide; anterior margin nearly truncate, whereas that of posterior margin sinuate; lateral margins arcuate, not crenulate; surface uniformly covered with dense and fine microsetae.

Elytra ( Fig. 1A ) short, wide, left elytron 0.28 mm long (from pronotal posterior margin to elytral apex along suture), together 0.49 mm wide, with only weakly sinuate posterior margins. Elytral epipleural keel absent. Mesocoxal cavities widely separated. Mesosternal area not well visible.

Legs ( Figs. 1 , 2A, G ) short, rather thick. Tibiae lacking tibial spines along outer edges, with hind tibial length of 0.19 mm. Metacoxae with well-developed ventral lamellae (sensu Yamamoto 2021). Tarsi shorter than tibiae, with tarsal formula 4-4-4. Metatarsus ( Fig. 2G ) slender; metatarsomere 1 shorter than the remaining three metatarsomeres combined.

Abdomen ( Figs. 1 , 2E, F ) short and broad, grad- ually tapering toward apex, widest at segment III, with six exposed tergites and sternites excluding terminalia. Tergites ( Figs. 1A , 2E, F ) covered with V- or U-shaped microreticulation; tergites III– VI each strongly transverse; tergite VIII with rounded apical margin. Abdominal segments III– VI each with two pairs of paratergites (not clearly visible on segment VII). Sternite VIII with gently rounded apical margin. Genitalia not visible .

Remarks. The newly found fossil specimen can be easily attributed to the aleocharine tribe Hypocyphtini by having antennae composed of 10 antennomeres and 4-segmented tarsi. The similar-looking mesoporine genera such as Mesoporus Cameron, 1959 and Anacyptus Horn, 1877 with 10 antennomeres all have 5-5-5 tarsi, nearly contiguous mesocoxae with an acute mesoventral process, and much larger metacoxal plates, among other differ- ences, so that group can be eliminated. Within Hypocyphtini , it is most reliably placed in the extant genus Cypha , which is characterized by the strongly transverse head (more than twice as wide as long) and the relatively large antennomere 10 that is at least as long as 8–9 together (but not usually as long as 7–9 together), while the other genera have a more elongate head and smaller antennomere 10. Cypha can be distinguished from Baltioligota Paśnik, 2005 (described from Baltic amber) by having less distinctly sinuate posterolateral margins of the elytra, a much larger antennal club, and a shorter metatarsomere 1 ( Paśnik 2005).

Syninclusion. A tiny spider (Araneae) is also embedded in the amber piece.

Figures

Fig. 1. Cypha sp. in Bitterfeld amber. A) Dorsal habitus, B) Ventral habitus. Scale bars = 0.5 mm.

Fig. 2. Cypha sp. in Bitterfeld amber. A) Forebody in ventral view, B) Left antenna, C) Left antenna and maxillary palpus, D) Maxillary palpus, E) Abdomen in dorsal view, F) Abdomen in dorsolateral view, G) Left metatibia and meta- tarsus. Abbreviations: a8–10 = antennomeres 8–10; mp3–4 = maxillary palpomeres 3–4; mtt1–4 = metatarsomeres 1–4.