Passandra septentrionaria, Bukejs, Andris & Alekseev, Vitalii I., 2016

Bukejs, Andris & Alekseev, Vitalii I., 2016, Passandra septentrionaria sp. nov.: the first described species of Passandridae (Coleoptera: Cucujoidea) from Eocene Baltic amber, Zootaxa 4144 (1), pp. 117-123 : 118-121

Passandra septentrionaria sp. nov.

( Figs 1–7 )

Type material. Holotype: Nr. RSM P3300.013 [ RSM], “ Holotype / Passandra septentrionaria sp. nov. / des. Bukejs A., Alekseev V.I. & McKellar R.C. ” [red printed label]; Yantarny village [formerly Palmnicken], the Sambian [Samland] peninsula, Kaliningrad region, Russia ; sex unknown. The complete beetle is included in a piece of amber that has been polished into a rhombic shape in order to create viewing planes (maximum length 10 mm, width 6 mm, and thickness 4 mm), and preserved without supplementary fixation. Ventral details are partly obscured by prominent drying line within amber that contains many particulates; thin veil of “milky” amber (created by decay products interacting with resin) is pervasive on ventral surface, but most anatomical details remain visible; much of the cuticle has carbonized and pulled away from the surface of the surrounding amber, creating silvery areas dorsally. Syninclusions: spider web (silk) fragments, and a few plant trichomes, separated during preparation and catalogued as specimen RSM P 3300.014.

Paratype: Nr. 1291 [ CAG], “ Paratype / Passandra septentrionaria sp. nov. / des. Bukejs A., Alekseev V.I. & McKellar R.C. ” [red printed label]; Baltic Sea coast, Gdańsk, Poland; sex unknown. The complete beetle is included in a small, elongate amber piece (length 29 mm, width 9 mm, and maximum thickness 5 mm), and preserved without supplementary fixation. Elytra and anterior part of head are partly obscured by a “milky” opacity; ventral part of specimen is almost not visible because of location of the beetle in amber piece. Syninclusions: leg of unidentified insect, and few small gas vesicles.

Type strata. Baltic amber, Blaue Erde deposits, mid-Eocene to Upper Eocene.

Type locality. Southeastern Baltic Sea coast.

Etymology. The specific epithet refers to the northern location of the specimen’s origin. It is formed after the Latin “ septentrionarius ”—northern.

Diagnosis. Passandra septentrionaria sp. nov. has pronotal sublateral lines only in basal one-third of pronotal length. In all extant species of Passandra , pronotal sublateral lines are more or less complete, except for in African species P. sexstriata Dalman, 1817 , which differs from the new species in (1) lacking admedian grooves and median process on head, (2) lacking pronotal sublateral lines, (3) pronotum with strongly prominent and acute anterior angles, (4) sublateral grooves on head well-defined and not joined to occipital groove, and (5) bicoloured body (rarely uniformly brown).

Description. Holotype. Body length 5.45 mm, maximum width 1.23 mm; body outline narrowly elongateoval, parallel sided, flattened dorsally, slightly convex ventrally; generally glabrous, unicolourous black, moderately shiny.

Head slightly convex, about 1.4× as wide as long, measured across compound eyes and along length of dorsal disc; covered with small and dense punctation, distance between punctures approximately 1–2× diameter of single puncture. Admedian grooves moderately deep, slightly diverging anteriorly, joined posteriorly to wide and deep occipital groove which contains shallow, broad foveae; medial process wide, slightly convex, triangular with widely rounded apex; sublateral grooves shallow and narrow but clearly impressed throughout their lengths, forming continuous lip around lateral and anterior margins of dorsal surface of head, and clearly joined to occipital groove. Clypeus narrow, slightly depressed, with emarginate anterior margin. Compound eyes small, about 1.2× as long as antennomere 1 is wide (in lateral view), subspherical, moderately convex.

Antennae with 11 antennomeres, moderately slender and long, extending to basal one-third of elytra; scape subcylindrical and somewhat globose, large, about 1.2× as long as wide; pedicel subquadratic, nearly as long as wide, 0.8× as long as antennomere 3; antennomeres 3–10 subcylindrical with mildly constricted bases, and markedly longer than wide, with long pale setae; antennomeres 5–6 narrowly grooved ventrally, and antennomeres 7–8 bear exceptionally faint longitudinal groove on ventral surface (other antennomeres are not clearly visible in either examined specimen); apical antennomere asymmetric, elongate-oval with broad apex, keeled, covered with setae. Setation absent from scape, but coarse setae are concentrated upon ventral and medial surfaces of subsequent antennomeres, and surround their apices; 3 or 4 short setae suberect on apex of pedicel; antennomere 3 with tuft of 20 or more suberect setae near apex, with lengths that exceed 1.5× width of antennomere; antennomere 4 with few apical setae as long as antennomere is wide, plus coarser, shorter setae dispersed along length and encircling apex of antennomere; antenommeres 5–8 bear similar setation to antennomere 4; antennomeres 9 and 10 apparently have reduced setae lengths; antennomere 11 has coarse, inclined setae basally, and encircling apex, plus dense coat of finer setae on asymmetrical apex.

Pronotum 1.13× as long as wide, subquadrate, nearly flat, widest in anterior one-third, distinctly narrowed posteriad; with small and dense longitudinally oval punctures (similar to punctures on head), disc with markedly sparser punctation. Sublateral lines present in basal one-third of pronotal length only. Lateral margins slightly convex, with narrow bordering; anterior margin sinuated, with faint bordering only present in medial one-third of width; posterior margin almost straight, with narrow bordering. Anterior angles obtuse, rounded, not protruding; posterior angles rectangular.

Scutellum moderately large, transverse, suboval. Elytra 2.5× as long as their combined width, and 2.7× as long as pronotum; base markedly wider than pronotal posterior margin. Elytral striae 1 and 6 complete: stria 1 grooved throughout entire length, stria 6 grooved in basal four-fifths of length; striae 2–5 indistinct (consisting of very fine punctures), grooved only faintly at base of elytra. Sutural interval convex; other intervals flat, smooth. Elytra of holotype appear to display microsculpture and large-scale colour patterns, but these are artefacts created by carbonization (cracking) of cuticle, and by cuticle adhering to surrounding amber only in a few patches, respectively.

Legs short and robust. Tarsal formula 5-5-5. Tarsomere 1 of all tarsi short, markedly shorter than tarsomere 2, partly covered by tibial apex; tarsomeres 2–4 short, subequal in length and shape; tarsomere 5 long, about as long as tarsomeres 3–4 combined; tarsomeres 2 and 3 of meso- and metatarsus with plantar comb of thick, inclined setae along apical margins, with comb most prominent at anterior and posterior corners, while tarsomeres 1 and 4 have reduced version of comb; low, broad spicules present along apex of metatibia. Claws simple, thin.

Paratype. Body length 8.5 mm; otherwise similar in all visible morphological characters to holotype.

Comment. Adult size varies significantly within some passandrid species, possibly due to the parasitic lifestyle of the larvae and different sizes of their hosts. For instance, adults of the extant Passandra sexstriata Dalman, 1817 can be 16–32 mm long; extant P. simplex (Murray, 1867) is 7–13 mm in length; the body length of the extant P. fasciata (Gray, 1832) varies in range 10–28 mm ( Ślipiński 1987). As in the recent species, we do not treat body size in the newly described fossil species as a species-specific character.

Figures

FIGURES 1 – 3. Passandra septentrionaria sp. nov., holotype: 1 — habitus, dorsal view; 2 — habitus, ventro-lateral view, 3 — habitus, dorso-lateral view. Scale bar = 1 mm.

FIGURES 4 – 7. Passandra septentrionaria sp. nov.: 4 — habitus, dorsal view, paratype; 5 — details of forebody, dorso-lateral view, holotype; 6 — apical antennomere, paratype; 7 — right antenna of holotype, the arrows indicate narrow grooves. Not reproduced to the same scale.