Silis (Silis) hegnai FANTI & M. G. PANKOWSKI, 2021

Fanti, Fabrizio & Pankowski, Maximilian G., 2021, Two new species of soldier beetles (Coleoptera, Cantharidae), the first from the tribe Silini in Dominican amber, Zootaxa 4996 (1), pp. 163-170 : 164-166

Silis (Silis) hegnai FANTI & M. G. PANKOWSKI sp. nov.

( Figs. 1–2 )

Description. Adult. Male winged, with large and elongated lateral lobes of the pronotum. Head and antennae blackish, pronotum and scutellum testaceous (probably yellow or red in life), elytra dark brown, legs brown. Body length: about 9.3 mm; elytra: 6.0 mm.

Head large, transverse, as wide as pronotum, slightly restricted and rounded behind the eyes, finely punctate and pubescent, partially covered by pronotum. Eyes sub-elliptical and strongly protruded, convex, inserted in upper and lateral part of head. Mandibles falciform. Maxillary palpi 4-segmented, palpomeres unequal in length with last palpomere strongly elongate and slightly securiform. Labial palps 3-segmented with last palpomere securiform. Antennae inserted in frons and away from eyes, reaching back to half of elytra, 11-segmented, filiform, all antennomeres wrinkled and covered with sparce setae; scape elongate, club-shaped; antennomere II (pedicel) short, approximately 1.5 times shorter than scape, thinner than scape and slightly thinner than the others; antennomere III slightly longer than second; antennomeres IV-VIII robust, slightly longer than antennomere III; antennomeres IX-X shorter than previous ones; antennomere XI filiform, oblong, with rounded apex. Pronotum almost as long as wide, surface undulating and thickened in the central disc, with semi-erect long setae and with small rugosity; margins and sides flat, anterior margin strongly rounded, posterior margin slightly rounded especially near the corners, sides with a kind of two lobes with a large groove in the middle of these. Scutellum triangular-shaped with pointed apex. Elytra wider than pronotum, elongate and reaching the last abdominal segments, parallel-sided, with slightly wrinkled microsculpture and some semi-erect setae, apex strongly rounded. Posterior wings almost completely covered by elytra. Metasternum sub-quadrate with undulating posterior margin; abdominal segments robust, transverse and pubescent; last tergite broad and rounded; last ventrite elongate, triangular-shaped and deeply divided forming two halves, with apex rounded. Legs slender and pubescent; coxae short and robust; trochanters robust with rounded apex; femora enlarged and almost straight; tibiae cylindrical, pro- and mesotibiae slightly shorter than pro- and mesofemora, metatibiae as long as metafemora, with an apical spur. Tarsal formula 5-5-5; first tarsomere very elongate; second tarsomere shorter than first; third tarsomere shorter and sturdier than tarsomere II; fourth tarsomere deeply bilobed at sides; fifth tarsomere elongate, slender and curved; proclaws with a small obtuse basal tooth, meso- and metaclaws simple without basal tooth. Female unknown.

Etymology. Species named after Dr. Thomas A. Hegna for his many contributions to paleontology and his selfless dedication to helping students succeed.

Holotype. Male , adult specimen in a Dominican amber piece: Catalog number MCZ: Ent:PALE-43616, in the Museum of Comparative Zoology ( MCZ) at Harvard University.

Type locality. The Cordillera Septentrional mountain range in the Dominican Republic, from the “Los Brachos” mine in the mining area known as “La Cumbre.”

Type horizon. Late Early/Middle Miocene; 15–20 million years ago (mya), probably close to 16 mya. La Toca Formation.

Syninclusions. Detritus and plant remains, a few air bubbles, an unidentified insect and an insect leg.

Systematic placement. The last maxillary palpomere securiform, the pronotum with lateral lobes/ apophyses, the abdomen with only eight visible urites, the elongated elytra, and meso- and metatarsal claws simple and without basal tooth, place this new species in the subfamily Silinae and the genus Silis ( Brancucci 1980; Ramsdale 2002; Constantin 2009, 2017). Its large size and the lateral margin of its pronotum without a minute glandular tuberosity also place Silis hegnai sp. nov. in the nominotypical subgenus Silis ( Constantin 2009) .

Differential diagnosis. Silis flavofemorata Wittmer, 1991 from the Dominican Republic is morphologically similar—albeit only vaguely—to Silis hegnai sp. nov. The new species shows a kind of broad concavity between the two lateral lobes that is not present in Silis flavofemorata ( Wittmer 1991a) . Furthermore, S. flavofemorata is smaller in size: 6–7 mm ( Wittmer 1991a). The only other Silis found in Miocene deposits is Silis chiapasensis Wittmer, 1963 from Mexican (Chiapas) amber ( Wittmer 1963). S. chiapasensis differs from Silis hegnai sp. nov. by the former species’ more transverse pronotum and the presence of a spine on each side, as well as for its considerably smaller body size than Silis hegnai sp. nov.

Remarks. The amber piece is extremely transparent, measures 20.7 x 15.6 x 6.2 mm and weighs 1.08 grams. The inclusion is complete and perfectly visible.

Figures

FIGURE 1. Silis (Silis) hegnai sp. nov. in Dominican amber.A: Holotype, dorsal view, scale bar = 1.0 mm. B: Holotype, ventral view, scale bar = 1.0 mm.

FIGURE 2. Silis (Silis) hegnai sp. nov. in Dominican amber. A: Holotype, detail of head, and pronotum, scale bar = 0.5 mm. B: Holotype, detail of elytral apex, scale bar = 0.5 mm. C: Holotype, detail of head and palps, scale bar = 0.5 mm. D: Holotype, detail of antennae, scale bar = 0.5 mm.