Malthodes (Malthodes) greenwalti, PANKOWSKI & Fanti, 2023

PANKOWSKI, MAXIMILIAN G. & Fanti, FABRIZIO FANTI, 2023, Six new species of fossil soldier beetles (Coleoptera: Cantharidae) from Eocene Baltic amber, Palaeoentomology 6 (3), pp. 300-312 : 309-310

Malthodes (Malthodes) greenwalti sp. nov.

( Figs 7 , 8 )

Holotype. Male , inclusion in Baltic amber, housed at the Smithsonian National Museum of Natural History, USNM PAL 787828 .

Syninclusions: Small air bubbles and debris.

Etymology. Species named in honor of Dr. Dale Greenwalt, researcher at the Smithsonian National Museum of Natural History, former president of the Washington Paleontological Society and much-admired mentor to the first author.

Diagnosis. This species belongs to the genus Malthodes based on its globular and distally pointed last maxillary palpomere, the very short and almost smooth elytra, head rounded behind the eyes, and the strongly modified last abdominal segments.

The new species is easily distinguished based on its last sternite (st9) that is elongated, wide and slightly folded and rounded in the apical margin. These features are not present in any known fossil Malthodes .

Locality and horizon. Amber mine in the Yantarny settlement, Sambian Peninsula, Kaliningrad Region, Russia. Middle Eocene (Lutetian) (47.8–41.2 Ma) to late Eocene (Priabonian) (37.8–33.9 Ma).

Description. Male, defined on the basis of the last urites strongly modified. Body length: 3.1 mm. Body entirely dark brown without yellow spots on elytra.

Head exposed, small, rounded, covered by dispersed setae. Eyes large, prominent, convex, rounded, located in the upper lateral part of head. Mandibles falciform, elongate. 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, not particularly long, surpassing the apex of elytra and half of abdomen; antennomere I very elongate, slightly club-shaped; antennomere II globular and only slightly elongate, short, about 2.1 times shorter than antennomere I; antennomere III short, about 1.3 times longer than antennomere II; antennomeres IV slightly longer than previous one; antennomeres V–IX subequal in length, slightly longer than antennomere IV; antennomere X slightly shorter than previous ones; antennomere XI elongate, thin, rounded at apex; all antennomeres covered by short and long setae. Pronotum transverse, wider than head, surface almost flat at center and slightly folded at sides and barely punctate with many short setae, sides straight and bordered and narrower before the posterior corners, posterior and anterior margins straight and strongly bordered, corners rounded. Elytra very short (revealing six tergites uncovered), wider than pronotum, covered with very shallow punctation and several short setae, parallel-sided, strongly rounded at apexes. Hind wings transparent, clearly exceeding the elytra and almost reaching the last abdominal segment. Legs slender, pubescent; coxae short, stout; trochanters elongate with rounded apex; femora enlarged, slightly curved; tibiae cylindrical and thin, protibiae longer than profemora, mesotibiae shorter than mesofemora, metatibiae longer than metafemora. Tarsomere I thin, elongate; tarsomere II about 1.4 times shorter than tarsomere I; tarsomere III shorter than second; tarsomere IV strongly bilobed; tarsomere V elongate, slightly curved, slender; claws simple without tooth. Metasternum subquadrate, slightly elongate, with the posterior margin protruded in the middle, covered with dispersed and short setae. Sternites transverse and pubescent. Penultimate tergite (tg9) wide, subrectangular; last tergite (tg10) narrower than penultimate tergite, elongate, slightly curved, with sides at apex with lobes that are short, robust and rounded; last sternite (st9) elongate, wide, almost flat, with the apical margin slightly folded and rounded. Aedeagus not visible. Female unknown.

Remarks. The yellow rectangular and elongated amber piece measures approximately 23 × 8 × 4.5 mm. The left antenna of the specimen is preserved until the seventh antennomere.

Figures

FIGURE 7. Malthodes (Malthodes) greenwalti sp. nov. in Baltic amber. Holotype (USNM PAL 787828). A, Dorso-lateral view, scale bar = 0.5 mm. B, Lateral view, scale bar = 0.5 mm. C, Detail of last sternites, scale bar = 0.3 mm. D, Detail of last sternites, scale bar = 0.1 mm.

FIGURE 8. Malthodes (Malthodes) greenwalti sp. nov. in Baltic amber. Holotype (USNM PAL 787828). Line drawing of the last abdominal segments, scale bar = 0.1 mm.