Mistran

Alekseev, Vitalii I. & Bukejs, Andris, 2016, New fossil genus of Silvanidae (Insecta: Coleoptera) from Baltic amber (Tertiary, Eocene), Zootaxa 4144 (1), pp. 101-108 : 103-107

Mistran ot sp. nov.

( Figs 1–5 )

Type material. Holotype: Nr. 1279-1 [CCHH]; possible female (hind femora simple). A complete beetle with partially exposed hind wings is included in a small, transparent yellow amber piece embedded in a block of GTSpolyester resin with dimensions 14 × 8 × 5 mm. Syninclusions (except one gas vesicle) are absent.

Type strata. Baltic Amber, Eocene.

Type locality. Yantarny settlement (formerly Palmnicken), Sambian (Samland) Peninsula, the Kaliningrad region, Russia.

Description. Body length about 2.55 mm, maximum width 0.9 mm; robust, elongate, nearly parallel-sided, slightly flattened dorsally; body and appendages uniformly black.

Head slightly longer than wide; vertex covered with irregular cells; frons and clypeus finely and sparcely punctate; punctures smaller than facets of eye, distance between punctures twice larger than puncture diameter. Anterior clypeal margin widely rounded. Compound eyes large, prominent, hemispherical, with coarse facets. Temples absent. Antennal grooves absent. Maxillary palpi short; terminal palpomere elongate, spindle-shaped, truncate, three times longer than penultimate one. Ultimate labial palpomere elongate and mucronate. Antennae stout, short, gradually thickened to apex; short, extending to middle of pronotum; 11-segmented with indistinct apparently 4-segmented club, densely covered with dark, fine semierect setae. Scape, pedicel and antennomere 3 conical, almost equal in size; antennomeres 4–6 transverse; antennomeres 7–9 subquadrate; antennomere 10 the widest; antennomere 11 rounded, as long as wide. Relative length ratios of antennomeres 1–11 equal to 5-5-5-4-4- 3-3-3-3-5-3.

Thorax. Pronotum subquadrate, almost as wide as long, finely bordered, disc flattened. Pronotal surface covered with irregular mostly four-sided cells (like on vertex); pronotum with three fine parallel longitudinal carinae (which divide the pronotum in almost equal quarters). Anterior and posterior margins arcuate; lateral margins almost parallel, crenulate, each side with six obtuse denticles; anterior and posterior angles obtuse, not prominent. Pronotal hypomera with shallow femoral grooves directed to posterior angles. Pro-, meso- and metaventrites densely punctured (distance between punctures equal to 0.25–0.30 × diameter of one puncture) and covered with dense secondary micropunctation. Pronotal hypomera sculptured like pronotum dorsally, covered with irregular cells. Procoxae nearly round. Procoxal cavities closed, mesocoxal cavities open, metacoxae do not extend laterally to meet the elytra. All coxae separated: procoxae separated by distance slightly wider than procoxal diameter; mesocoxae separated by distance approximately 0.5 × of coxal diameter; metacoxae almost contiguous. Prosternal process elongate, strongly dilated apically, truncate.

Scutellar shield distinct, strongly transverse, 3 × as wide as long. Elytra together 1.8 × as long as wide, elongate, subparallel, at humeri slightly wider than pronotum, separately rounded apically, finely pubescent. The sutural area in apical one-third weakly impressed. Humeral angles rounded. Each elytron with four entire (non-interrupted) fine and straight carinae (raised interstriae 3, 5, 7, 9), third carina not reaching elytral apex; and with 10 rows of punctures, strial punctures small, oval, oblique, with intervals about 1.0 × puncture diameter; scutellary striole not distinct. Lateral margins narrowly explanate. Epipleura well developed, reaching apex of ventrite 4, widest at humeral angle, with 3–4 rows of small punctures. Hind wings present. The ratio of lengths of mesoventrite to metaventrite to abdomen: 6-13-35.

Abdomen with five visible, similarly articulated, finely pubescent ventrites. Relative lengths (medially) of ventrites 1–5 equal to 25-15-10-9-11. All ventrites finely and densely punctured; ventrite 5 rounded apically. Intercoxal process of abdominal ventrite 1 triangular and acute.

Legs robust, short ( Fig. 5 ). Femora incrassate; hind femora simple (without denticle or tooth). Tarsal formula 5-5-5. No tarsomeres lobed. Length of apical tarsomere subequal to combined length of tarsomeres 1–4; tarsomere 4 the smallest; tarsomeres 1–3 broad, almost equal in size. Tarsal claws thickened basally, large, equal in size, length about one-third of apical tarsomere.

Remark. The femoral lines of ventrite 1 (an important character for diagnosis) are not visible on the specimen because of the position of the legs.

Etymology. The species name is an abbreviation used as noun in apposition. “OT” is an abbreviation of the Latin “Ordo Teutonicus” (official names: Latin: Ordo domus Sanctae Mariae Theutonicorum Hierosolymitanorum, German: Orden der Brüder vom Deutschen Haus der Heiligen Maria in Jerusalem, English: the Order of the Teutonic Knights of St. Mary's Hospital in Jerusalem). The Teutonic Order was the German medieval military order created the independent Monastic State of the Teutonic Knights in the conquered territory of the South- Eastern Baltic region during the Northern Crusades.

Taxon References Fossil Type Locality Age A wide variety of lifestyles is represented in extant representatives of the subfamily Silvaninae , including subcortical fungus feeding, leaf litter dwelling, ant inquilinism, facultative predation and seed feeding. The majority of Silvaninae are subcorticolous in the natural habitat ( McElrath et al. 2015). In all likelihood, the fossil Mistran ot was fungivorous and inhabited the microhabitat under loosened bark on dead trees in the Eocene “amber forest”.

The newly described genus Mistran is apparently close to the genus Nausibius , also reported from Baltic amber (primarily by Klebs 1910). However, the studied beetle merits the separate generic level for the reasons mentioned in the diagnosis. The presence of the extant genus Nausibius in Eocene Europe is under question and should be confirmed.

A checklist of fossil Silvanidae is compiled and provided ( Table 1 ). The oldest representative of the family currently known is from the Cretaceous Lebanese amber.

Ermisch (1942) described one species assigned by him to Airaphilus Redtenbacher, 1858 (Silvaninae) from Baltic amber. The description is quite detailed, but some important characters of ventral side (e.g. distance between coxae, closeness or openness of coxal cavities) and shape of scutellum are not mentioned. The correct generic and subfamily placement of Airaphilus denticollis Ermisch, 1942 is doubtful to our opinion. Judging by the photo in the original description (primarily the shape of the pronotum, antennae and head) and described well-marked frontal grooves [“ An den Seiten des Kopfes, innerhalb der Augen, befindet sich jederseits eine seichte, nach vorn konvergierende Furche, die sich über den flachen Beulen oberhalb der Fühlereinlenkung etwas grubenartig erweitert.”], we conclude that this species does not belong to Airaphilus and is not a member of subfamily Silvaninae . Probably, the beetle described as Airaphilus denticollis should be assigned to the tribe Telephanini LeConte, 1861 within subfamily Brontinae and should be placed in the genus Psammoecus Latreille, 1829 (habitus similar, scutellary striole apparently absent) or is close to it (M. Thomas, pers. comm.). A detailed study of the type material or designation of neotype (because the type specimen was likely lost during World War II and it is quite possible that the holotype does not exist anymore) is needed. In present study and compiled checklist, we leave it as described by Ermisch (1942) without formal systematic change, because we lack sufficient proof to do so presently.

Figures

FIGURES 1 – 3. Mistran ot gen. et sp. nov., holotype: 1 — habitus, dorsal view; 2 — habitus, ventral view; 3 — habitus, lateral view.

FIGURES 4 – 5. Mistran ot gen. et sp. nov., reconstruction: 4 — habitus, dorsal view; 5 — foreleg.

Tables

TABLE 1. Check-list of fossil Silvanidae.

Silvanidae	Peris et al. 2013, 2016	Spanish amber	Peñacerrada I, and San Just (Spain)	100–112 Ma
Silvanidae	Kulicka & Ślipiński 1996	Baltic amber	Kaliningrad region (Russia)	37.2–33.9 Ma
Brontinae
Antiphloeus stramineus	Kirejtshuk & Nel 2013	Oise amber	Oise department (France)	55.8–48.6 Ma
Cryptamorpha sp.	Hieke & Pietrzeniuk 1984	Bitterfeld amber	Goitzsche/Bitterfeld (Germany)	37.2–33.9 Ma
Dendrobrontes popovi	Kirejtshuk 2011; Alekseev 2013	Baltic amber	Kaliningrad region (Russia)	37.2–33.9 Ma
Silvaninae
Silvaninae	Kirejtshuk & Azar 2013	Lebanese amber	Hammana – Mdeirij and Nabaa Es-Sukkar – Brissa (Lebanon)	129–113 Ma
Airaphilus denticollis	Ermisch 1942; Spahr 1981; Alekseev 2013	Baltic amber	Kaliningrad region (Russia)	37.2–33.9 Ma
Airaphilus sp.	Klebs 1910; Handlirsch 1925; Bachofen-Echt 1949; Larsson 1978; Spahr, 1981;	Baltic amber	Kaliningrad region (Russia)	37.2–33.9 Ma
Mistran ot	present paper	Baltic amber	Kaliningrad region (Russia)	37.2–33.9 Ma
Nausibius sp.	Klebs 1910; Bachofen-Echt 1949: Larsson 1978; Spahr 1981	Baltic amber	Kaliningrad region (Russia)	37.2–33.9 Ma
Pleuroceratos burmiticus	Poinar et al. 2008	Burmese amber	Myanmar/Burma	100–94 Ma
Silvanus sp.	Hope 1836; Berendt 1845; Giebel 1852, 1856a, 1856b; Menge 1856; Motschulsky 1856; Scudder 1885, 1886, 1891; Helm 1896; Handlirsch 1908, 1925; Klebs 1910; Bachofen-Echt 1949; Larsson 1978; Spahr 1981	Baltic amber	Kaliningrad region (Russia)	37.2–33.9 Ma
Subfamilia incerta
Sinisilvana fushunensis	Hong 2002; Kirejtshuk 2011	Fushun amber	Guchengzi, Liaoning Province (China)	55.8–48.6 Ma
Discussion