Phyllodrepa daedali Shavrin & Yamamoto

Shavrin, Alexey V. & Yamamoto, Shuhei, 2019, Unexpected palaeodiversity of omaliine rove beetles in Eocene Baltic amber (Coleoptera, Staphylinidae, Omaliinae), ZooKeys 863, pp. 35-83 : 35

† Phyllodrepa daedali Shavrin & Yamamoto sp. nov. Figures 7-9, 54-56, 57-64

Type materials examined.

Holotype (male), FMNHINS-3260629, complete specimen as inclusion in very small piece of light yellow Baltic amber, 9.3 mm × 5.9 mm × 2.9 mm in size (Figs 7-9), with the following labels: "16 [printed] 02 [handwritten] SYAC 0 [printed] 294 [handwritten] | Baltic / Burmite | Other: | Larva / Adult | Omalium sp. [handwritten] | Omaliinae [handwritten] | Yantarny, Kaliningrad [handwritten] | Shûhei Yamamoto’s | Amber Collection" <large rectangular label, printed>, "[FMNH barcode at left side of label] FMNHINS | 3260629 | AMBER [handwritten] | FIELD MUSEUM | Wet" <small rectangular label, printed>, "HOLOTYPE | Phyllodrepa | daedali sp. nov. | Shavrin A. & Yamamoto S. des. 2019" <red rectangular label, printed> (FMNH).

Preservation.

The specimen is relatively well preserved and many details are visible, from the dorsal, ventral and lateral sides (Figs 7-9). However, most body parts, except the dorsal surface of the head, are covered with cloud of milky substance, especially most of the ventral side.

Locality and horizon.

Baltic amber from Yantarny, Kaliningrad, westernmost Russia; mid-Eocene (ca 44 Ma; Wappler 2005).

Description.

Measurements: HW: 0.32; HL: 0.22; OL: 0.11; AL: 0.52; PML × PMW (III, IV): III: 0.02 × 0.02, IV: 0.07 × 0.02; PL: 0.35; PW: 0.48; ESL: 0.56; EW: 0.51; MTbL: 0.31; MTrL: 0.20 ( I–IV: 0.08; V: 0.12); AW: 0.50; TL: ~1.80. Antennomeres with lengths × widths: 1: 0.08 × 0.03; 2: 0.06 × 0.02; 3-4: 0.05 × 0.02; 5: 0.04 × 0.02; 6: 0.04 × 0.03; 7: 0.03 × 0.03; 8-10: 0.03 × 0.04; 11: 0.08 × 0.04.

Body elongate and slightly convex, glossy (Fig. 54), reddish-brown, with darker head and abdomen; mouthparts, antennae, legs and apical margins of abdominal sclerites yellow-brown. Body lateroventrally as in Figure 55 and laterally as in Figure 56. Lateral margins of pronotum (Figs 54, 57), paratergites and abdominal tergite VIII (Fig. 64) with several long erect setae.

Head 1.4 times as wide as long, with slightly convex median portion and slight oval lateroapical impressions (Fig. 57), with sparse, small and moderately deep punctation, with shallow postocular carina. Eyes large and broadly convex (Figs 55-57, 60). Ocelli large and convex, situated at level of posterior margins of eyes, distance between ocelli much more than twice as long as distance between ocellus and posterior margin of eye; grooves in front of ocelli present, moderately deep and short (Fig. 57). Apical segment of maxillary palp significantly longer than small penultimate segment, from swollen middle gradually narrowing apicad (Figs 56, 57, 63). Antenna moderately short, just surpassing basal margin of pronotum, with sparse very long setae on antennomeres 5-11; basal and antennomere 2 swollen and elongate, 3 and 4 narrow and elongate, 5 ovoid, 6 and 7 slightly transverse and 8-10 distinctly transverse, apical antennomere large, strongly narrowing from about middle apicad (Figs 54-58).

Pronotum slightly convex, without longitudinal impressions, 1.3 times as wide as long, 1.5 times as wide as head, from middle distinctly more narrowed posterad than apicad, with widely rounded anterior and obtuse posterior angles; apical margin widely rounded, slightly shorter than somewhat straight posterior margin; lateral margins slightly sinuate posteriorly, narrowly emarginate and finely crenulate; lateroposterior portions with indistinct, moderately wide impressions (Figs 54, 57). Dorsal surface of pronotum without visible microsculpture between punctures, with dense, very large and deep punctation, markedly sparser in lateral and smaller in apical and basal portions (Figs 54, 57). Prosternum with wide procoxal fissures and moderately short prosternal process, with acute apex (Fig. 60). Scutellum moderately large, triangular, with somewhat rounded apex, without visible punctures or microsculpture (Fig. 54).

Elytra slightly convex, longer than wide, 1.6 times as long as pronotum, reaching basal margin of abdominal tergite IV, with somewhat parallel lateral sides and widely rounded lateroapical angles, with sutural apices truncate to very oblique (Fig. 54). Punctation as that in pronotum, but shallower and somewhat smoothed on apical portion, smaller and sparser on basal and apical portions. Surface between punctures with shallow dense isodiametric microsculpture.

Legs long and slender, similar in shape, with moderately wide femora; tibiae slender, gradually widened apicad, covered by elongate setae, denser and stronger on inner margins, and with a few strong spines near apex and additional spine on outer margin in apical third (Figs 55, 56, 59); tarsi long, with apical metatarsomere distinctly longer than previous tarsomeres together (Figs 59, 61, 62); protarsus as in Figure 61, with long tenent setae (probably only in males); tarsal claw simple (Figs 61, 62).

Abdomen markedly convex, slightly narrower at base than elytra; wing-folding patches in middle of tergite IV and/or V not visible; intersegmental membranes between tergites IV–VII with brick-wall sculpture, apical margin of tergite VII with indistinct very narrow palisade fringe (Fig. 54). Abdominal tergites without visible punctation, with large distinct transverse microsculpture.

Male. First four protarsomeres wide (Figs 55, 59, 61); ventral surface of protarsomeres 1-4 with several rows of modified tenent setae (not all details visible) consisting of internal rows formed by markedly elongate setae with leaf-shaped apical parts (Figs 55, 56, 59, 61); ventral surface of mesotarsomeres 1-4 with two rows of elongate setae with broadened apical parts as that in protarsomeres 1-4 but without additional internal rows (Figs 55, 56); metatarsi as in Figure 62. Apical margin of abdominal tergite VIII straight.

Female unknown.

Etymology.

The specific epithet is the Latinized name of Daedalus , -i, m, the Greek architect of the times of Theseus and Minos, and father of Icarus.

Remarks.

In external characters such as proportions of the body, antennomeres, and maxillary palpomeres, and, more substantially, by the proportions of tarsi with elongate apical tarsomere, the fossil undoubtedly belongs to the tribe Omaliini . Based on the triangular and elongate apical maxillary palpomere, shape of slightly convex head and slightly transverse antennomere 7, presence of two small depressions between bases of antennae, short grooves (dorsal tentorial pits) in front of the ocelli, and shape of the moderately convex pronotum with slightly sinuate lateral margins in front of obtuse posterior angles, the new species belong to the Phyllodrepa complex, specifically to the genus Phyllodrepa . Phyllodrepa includes about 30 species distributed in Palaearctic, Nearctic, and Neotropical regions ( Newton et al. 2000; Herman 2001; Schülke and Smetana 2015). The genus requires a worldwide revision and apparently includes some taxa that belong to other related genera ( Shavrin 2016; Zanetti et. al. 2016). Phyllodrepa daedali sp. nov. and Ph. icari sp. nov., described below, are species with a very small and pale body that reminds of some Palaearctic species of the genus Dropephylla Mulsant & Rey, 1880, that for a long time had been regarded as a subgenus of Phyllodrepa . Nevertheless, species of Dropephylla differ by the absence of grooves in front of ocelli and microsculpture on the elytra, wider apical maxillary palpomere, oval antennomere 4, by the presence of moderately defined short and rounded temples, shorter apical tarsomere, and other morphological characters that were considered in the revision of the Palaearctic fauna of the genus by Jászay and Hlaváč (2006). Although faintly crenulate lateral margins of the pronotum (Fig. 57) are similar to those in Dialycera Ganglbauer and Hapalaraea Thomson ( Zanetti 1987, 2012b; Zanetti et al. 2016), they are also known to the first author in European Phyllodrepa puberula Bernhauer, 1903 and some little-known species distributed in the eastern Palaearctic Region. Despite this, the new species can not be reliably associated with any extant species of the genus due to its unique morphological characters and the fact that most species differ only by the external structure of the aedeagus. Both new species of Phyllodrepa described herein differ from the more ancient Transbaikal † Eophyllodrepa Ryvkin from the Middle-Upper Jurassic of Novospasskoe ( Ryvkin 1985) and † Daidromus Ryvkin from the Upper Jurassic of Daya ( Ryvkin 1990), by the same morphological characters as in Ph. electrica (see Zanetti et al. 2016). Based on the small body, shape of head, general shape of apical antennomeres, and pronotum with finely crenulate lateral margins, Ph. daedalum sp. nov. is similar to Ph. antiqua Zanetti, Perreau & Solodovnikov, 2016, which was recently described from Baltic amber ( Zanetti et. al 2016). It is also similar to Ph. icari sp. nov. (see below), based on the crenulate lateral pronotal margins, pale body, and large and deep punctation of the elytra. It differs from Ph. antiqua by the smaller, paler and slightly more convex body (Figs 54, 56), coarser and deeper punctation of pronotum (Figs 54, 57) and elytra (Fig. 54), and elongate antennomeres 2-5 (Fig. 58), and from Ph. icari sp. nov. by the darker abdomen, wider apical maxillary palpomere (Fig. 57), shape of anterior angles of the pronotum not protruded apicad (Fig. 57), denser punctation of the pronotum, less transverse head and pronotum (Fig. 57), and longer antennomeres 4-5 and 11 (Fig. 58). From both these species it differs by longer elytra, and from Ph. antiqua by the presence of modified setae on tarsomeres 1-4 of front and middle legs of the male.

A remarkable morphological feature of Ph. daedali sp. nov. is the presence of modified rows of elongate setae (Figs 55, 56, 61) with leaf-shaped apical parts on ventral surface of pro- and mesotarsomeres 1-4, described earlier as disco-setae ( Stork 1980) or clavate adhesive setae ( Smetana 1987). Similar structures were observed in species of the Oriental genera Xanthonomus Bernhauer by Steel (1955: fig. 6), Prosopaspis Smetana ( Smetana 1987: fig. 22), Duocalcar Peris & Thayer, 2014 (at least protarsi), and Paraphloeostiba ( Steel 1960a).