Yethiha pubescens Simon Prazak & Lackner, 2023

Simon Prazak, Jan, Fikacek, Martin, Prokop, Jakub & Lackner, Tomas, 2023, Under the Cretaceous bark: Fossil evidence for the ancient origin of subcortical lifestyle of clown beetles (Coleoptera: Histeridae), Arthropod Systematics & amp; Phylogeny 81, pp. 439-453 : 439

Yethiha pubescens Simon Prazak & Lackner sp. nov.

Type material.

Holotype specimen (1410/E), unknown sex, Northern Myanmar, inclusion in burmite (ca. 99 Ma), amber piece clear, ca. 14x5x1 mm, without synclusions.

Description.

Measurements. Head width: 0.25 mm, width between anterior pronotal angles: 0.29 mm, width between posterior pronotal angles: 0.61 mm, pronotal length: 0.33 mm, elytral length: 0.6 mm, elytral width (across widest point): 0.7 mm. - Body round, strongly convex dorsally; dorsum with visible pubescence. Colour dark reddish brown, covered with white debris. - Head. Supraorbital area with a row of prominent setae continuous along the occipital ridge. Clypeus densely setose, setae prominent. Labrum subtrapezoidal, lateral margins rounded, labral disc multisetose, with a prominent long seta (approximately 3 × as long as the remaining labral setae) on each side. Outer lateral margin of mandible setose. Mandibular apex acute, each mandible with a prominent subapical tooth; mandibular prostheca well developed. Maxillary galea round, setose, lacinia setose, with a clearly developed lacinial fringe. Lacinial hook (uncus) well developed, prominent. Terminal maxillary palpomere long and slender. Terminal labial palpomere thickened, pointed apically. Antennal scape thick. Pedicel thickened, approximately as long as antennomeres 3-5 combined. Antennomere 8 dilated. Each antennomere 3-8 with at least two prominent setae. Antennal club rounded, flattened, densely setose, sparse long setae intermingled with short denser setae, with 2 clearly visible sutures. Eyes flattened, well visible from above. - Thorax. Base of the pronotum with sparse microscopic setation (setae 20 microns long). Marginal pronotal stria present, complete. Basal margin almost rounded, slightly pointed. Scutellum invisible. Elytral base, apex and elytral disc pubescent. Setae brown, each located in a pore, separated approximately by four times of the pore diameter. Elytral flanks with shorter and denser setation. Elytral epipleuron with a single well-developed complete stria. Other striation not visible. Prosternal lobe short and broad, incised laterally for the antennal passage. Antennal cavities widely open anteriorly. Prosternal process square shaped. Prosternal striation not visible. Mesoventrite short and wide (4x wider than long). Mesoventral striation not visible. Metaventrite very large, broad, convex, with scattered irregular shallow punctures. Lateral metaventral stria absent. Post mesocoxal striae present, thin, attaining metepisternum. - Abdomen. Propygidium almost entirely covered with elytra. Pygidium covered with debris. - Legs. Profemur with a deep groove for protibial reception. Protibia very broad with short denticles along the outer margin and very short thick setae along inner margin. Protibial spur thick, prominent. Protarsal groove developed, margined by another row of prominent setae. Terminal protarsomere as long as protarsomeres 1-4 combined. Tarsal claws short, approximately one third of the terminal tarsomere length. Mesotibia slender, outer margin with relatively long sparse denticles, diminishing in size in basal direction. Inner margin with a row of short thick setae. Tarsal groove not present. Tarsal claws short, approximately one third of the terminal tarsomere length. Metatibia and metafemur largely similar to mesotibia and mesofemur. Terminal metatarsomere significantly thickened. Tarsal claws short, approximately half of the terminal metatarsomere length.

Taxonomic assignment.

The present species falls within the recently described genus Yethiha Caterino, 2021 based on the strongly convex dorsum lacking striae and carinae, invisible scutellum (observed by Caterino (2021) as "tiny or absent") and broad protibia with a prominent apical spur.

According to the phylogenetic analyses, genus Yethiha proved to be a part of the Dendrophilinae as suggested by Caterino (2021). In our analyses (Fig. 5 ), it was revealed as closely related to the extant Dendrophilus Leach, 1817 and the extinct Druantia Caterino, 2021 (Fig. 5 ). Future analyses would be required in order to unequivocally place Yethiha into an existing dendrophiline tribe.

Differential diagnosis.

Yethiha pubescens sp. nov. differs from Y. peregrina Caterino, 2021 by the presence of elytral and pronotal pubescence (Fig. 4F ). Head pubescence is also denser and more prominent than that of Y. peregrina . Furthermore, the present species is characterised by prominent thick setae on the inner and more robust denticles on the outer protibial margin. Meso- and metatibiae are likewise significantly more robust (Fig. 4B ; width:length ratio in Y. peregrina : mesotarsomeres 1-4: 2:5, mesotarsomere 5: 1:5, metatarsomeres 1-4: 1:2-3, metatarsomere 5: 3:10; width:length ration in Y. pubescens : mesotarsomeres 1-4: 1:1, mesotarsomere 5: 1:2, metatarsomeres 1-4: 1:1, metatarsomere 5: 1:2).

Etymology.

Latin term pubescens refers to the hirsute cuticle of the species.

Figures

Figure 4. Yethiha pubescens Simon Prazak & Lackner sp. nov. A dorsal view; B ventral view; C head, frontal view; D ditto, oblique view; E flagellum; F elytral setation; G amber specimen.

Figure 5. Maximum parsimony analysis of the position of known fossil species of the Histeridae. A the complete tree showing the position of the fossils and the current subfamily classification of the lineages; B Dendrophilinae part of the tree with mapped characters; C Histerinae part of the tree with mapped characters. Bold taxa = fossils, red taxa = fossils described in this paper. For characters see Zhou et al. (2020).