Malthinus (Malthinus) masoni M. G. PANKOWSKI & FANTI, 2022

Pankowski, Maximilian G. & Fanti, Fabrizio, 2022, Two new fossil species of soldier beetles (Coleoptera, Cantharidae, Malthininae) from Baltic amber, Zootaxa 5165 (4), pp. 548-556 : 549-550

Malthinus (Malthinus) masoni M. G. PANKOWSKI & FANTI sp. nov.

( Figs. 1–2 )

Description. Adult, winged, female defined on the basis of the short antennae and wide last sternite (not triangular shaped). Body length: 4.4 mm. Entirely dark brown-blackish without yellow spots on elytra, and with head and pronotum lighter brown and covered by black lines and marks.

Head exposed, strongly narrowed behind eyes, very strongly rugose, with deep and wide punctation and very few setae. Eyes very large, prominent, convex, rounded, inserted in the lateral-upper part of head. Mandibles falciform, elongated, thin. Maxillary palpi 4-segmented, with last palpomere globular and distally pointed. Labial palpi 3-segmented, with last palpomere globular and distally pointed. Antennae filiform, 11-segmented, short, reaching and surpassing two thirds of elytra; antennomere I elongated and nearly as long as the sum of antennomeres II and III, club-shaped; antennomere II about 1.7 times shorter than antennomere I; antennomeres III-V about 1.3 times longer than antennomere II; antennomeres VI-X subequal in length, millimetrically shorter than previous ones; antennomere XI elongated, very slightly pointed; all antennomeres covered by short setae. Pronotum as wide as long, narrower than head, rugose, surface slightly undulate and deeply impressed punctate, equipped with short setae, sides straight and strongly bordered, posterior and anterior margin straight and strongly bordered. Elytra short (revealing three abdominal segments uncovered), wider than pronotum, covered with deep punctation and some erect setae, parallel-sided, strongly rounded at apex. Hind wings slightly infuscate, exceeding the elytra and covering last two abdominal segments. Legs slender, pubescent; coxae short, stout; trochanters slightly elongated with rounded apex; femora enlarged, rather straight; tibiae cylindrical and thin, pro- and mesotibiae shorter than pro- and mesofemora, metatibiae longer than metafemora. Tarsi 5-segmented, pubescent; tarsomere I thin, elongated; tarsomere II about 1.5 times shorter than tarsomere I; tarsomere III very short, triangular-shaped; tarsomere IV strongly bilobed; tarsomere V elongated, slightly curved, slender; claws simple without tooth. Metasternum with rounded posterior margin, covered with many dispersed, very short setae and very shallow punctation. Sternites transverse and pubescent. Last tergite short, transverse, rounded apically; last sternite as wide as last tergite, rounded apically. Male unknown.

Etymology. Species named after Dr. R. Bryan Mason, a gifted neurosurgeon in Maryland who operated on the first author’s mother and successfully removed her brain tumor.

Holotype. Female , inclusion in Baltic amber, housed at the Smithsonian National Museum of Natural History in Washington, DC, USA, under catalog No. 775570.

Type locality. Amber mine in the Yantarny settlement, Sambian Peninsula, Kaliningrad Region, Russia.

Type horizon. Middle Eocene (Lutetian) (47.8–41.2 Ma) to late Eocene (Priabonian) (37.8–33.9 Ma).

Syninclusions. Detritus, botanical fragments, air bubbles and a few stellate hairs.

Systematic placement. The new, extinct species clearly belongs in the subfamily Malthininae based on its last maxillary palpomere that is globular and pointed distally. Characters including its triangular head behind the eyes, filiform antennae, long elytra and unmodified terminalia place the new species in the genus Malthinus .

Differential diagnosis. No sister group of Malthinus masoni sp. nov. has been found living in the Baltic region or Central Europe, and no other fossil species of Malthinus exhibits the same characters as the new species. Malthinus masoni sp. nov. differs from the fossil species Malthinus danieli Kuśka & Kania, 2010 in its coloration: Malthinus danieli has a lighter pronotum with a black spot on the posterior half, and it has pale yellow-brown tibiae and dark femora ( Kuśka & Kania 2010). The new species also differs by its pronotum with straight sides: The pronotum is narrower anteriorly in Malthinus danieli ( Kuśka & Kania 2010) . Compared to the new species described here, Malthinus rifbjergi Fanti & Damgaard, 2018 has a more transverse pronotum (1.5:1 vs. 1:1), as well as different lengths and slightly different shapes of its antennomeres ( Fanti & Damgaard 2018). In the new species, for example, antennomeres II is shorter (in comparison to the other 10 antennomeres) and more club shaped than in Malthinus rifbjergi .

Remarks. The yellow rectangular amber piece measures approximately 27x16x 5 mm and weighs 1.5 grams. The inclusion is complete and clearly visible. The amber piece has some superficial cracks.

Figures

FIGURE 1. Malthinus (Malthinus) masoni sp. nov. A: Holotype, habitus, dorsal view, scale bar = 1.0 mm. B: Holotype, habitus, dorsal view (detail), scale bar = 0.5 mm.

FIGURE 2. Malthinus (Malthinus) masoni sp. nov. A: Holotype, habitus, ventral view, scale bar = 1.0 mm. B: Holotype, habitus, ventral view (detail), scale bar = 0.5 mm.