Platycretus muscularis Simon Pražák & Lackner, sp. nov.

Body rectangular, flattened, dorsally with large irregular depressions. Labrum asetose, without punctures. Mandibles massive, carinate, outer margin almost perpendicular. Pronotum with a complete marginal pronotal stria, basal fragment of outer lateral stria and incomplete inner lateral stria interrupted at anterior pronotal angles. Prosternal lobe present, massive. Antennal cavity present, partially closed by prosternal alae. Elytra with a complete, deeply impressed marginal elytral stria. Tibiae very broad, without teeth, with denticles along their outer margins. Meso- and metafemora extremely thickened, triangular in cross section.

Name of the genus was chosen to point out its Cretaceous origin and flattened shape.

Holotype specimen (1407/E), unknown sex, Northern Myanmar, inclusion in burmite, Cenomanian (ca. 99 Ma), amber piece somewhat opaque, with significant amount of debris and bubbles, ca. 6×4×2 mm, synclusions: plant material, minute seeds, unidentified insect fragments.

Measurements. Head width: 0.2 mm, width between anterior pronotal angles: 0.41 mm, width between pronotal prosternal angles: 0.93 mm, pronotal length: 0.75 mm, elytral length: 1.11 mm, elytral width (across widest point): 0.93 mm. — Body. Rectangular, flattened, dorsal cuticle wholly covered with irregular prominent tubercles and depressions. Cuticle pitch black, legs chestnut brown. — Head. Frons with deep anteromedian depression, punctate. Supraorbital stria present, carinate. Frontal stria carinate, widely interrupted medially, extending to the clypeolabral suture, convergent anteriorly. Mandibles stout, massive, outer margin almost perpendicular, carinate. Labrum long, almost square-shaped, asetose, without punctures, appears to be fused with clypeus. Left mandible with acute prominent tip, rest of the mandibles invisible. Terminal maxillary palpomere thin and long, flattened. Remaining mouthparts unobservable. Scape curved, as long as antennomeres 2–8 combined, outer margin distinctly carinate. Pedicel slightly longer than antennomere 3. Antennomeres 3–8 short, becoming wider apically. Antennal club large, round, covered with a velvet-like white layer (short setation). Two intersegmental sutures of antennal club visible, straight. Eyes flattened. — Thorax. Pronotum rectangular, very wide, flat, with large depressions and irregular large shallow punctures of various sizes mostly in the anterolateral region. Anterior pronotal angles prominent, obtuse. Basal margin of pronotum significantly curved posteriorly. Lateral edges parallel with and subsequent to the lateral edges of elytra. Marginal pronotal stria complete. Outer lateral stria present as a short thin basal fragment reaching approximately 1/3 of pronotal length apically. Inner lateral pronotal stria deeply impressed, complete laterally, absent anteriorly (interrupted at the anterolateral angles of the pronotum). Surface between marginal and lateral pronotal striae convex. Scutellar shield small, triangular. Elytra without punctuation, with extensive depressions covering its entire dorsal area. Marginal elytral stria deeply impressed, complete, wider anteriorly. Dorsal striae I and II faintly present on posterior half of elytra. Elytral epipleural stria complete, carinate. Prosternal lobe large, broad, delicately punctuate, with two thin transverse lines. Anterior prosternal margin almost straight medially. Marginal prosternal stria not distinguishable. Prosternal process obfuscated by debris. Antennal cavity present, partially closed by prosternal alae. Mesoventrite with irregular depressions, surface structures unclear. Meso-metaventral area with large depression, most likely caused by external factors (and hence likely representing an artefact), making the striation on mesoventrite and metaventrite indiscernible. Metaventrite with shallow punctures. Metepisternum depressed and irregularly sculptured. — Abdomen. First visible abdominal ventrite square-shaped, with deep punctures separated by their diameter. Rest of abdomen missing. — Legs. Profemur flat. Protibia flat and very broad, with 6 short and thick denticles on outer margin. Protarsal groove present, faintly S-shaped. Protibial spur well developed. Protarsus short. Mesofemur massively thickened, triangular in cross section. Mesotibia relatively short (shorter than mesofemur), flat and very broad (broader than protibia), with short thick denticles along its outer margin. Mesotarsus not visible. Metafemur very thickened, triangular in cross section. Metatibia largely similar to mesotibia but not as wide, with short thick denticles and numerous shorter setae along the outer margin. Large accumulation of short slender denticles present apically around the metatibia-metatarsal articulation. Metatarsus long (about 3/4 of the metatibial length).

The present species undoubtedly belongs to the subfamily Histerinae due to the combination of the following characters: asetose and impunctate labrum (Fig. 1D), well-developed prosternal lobe, antennal cavity partially closed by prosternal alae (Fig. 1D, E).

Figure 1. 

Platycretus muscularis Simon Pražák & Lackner, gen. & sp. nov. A dorsal view; B amber specimen; C mouthparts; D frontal view; E foreleg; F middle leg; G hind leg; H cross section at the breakage point – posterior part.

Platycretus muscularis was resolved as sister group to Haeteriinae in the phylogenetic analyses. They share several synapomorphies – very wide profemur and long, square shaped labrum which appears to be fused with clypeus (see Fig. 5C). However, the species lacks other defining characters of the Haeteriinae – namely the robust triangular scape. Some characters important for tribal assignment (e.g., meso- and metaventrite) are obfuscated.

The Latin adjective muscularis (muscular) refers to the thickened meso- and metafemora most likely accommodating a large amount of muscle tissue.

Subfamily Dendrophilinae Reitter, 1909

Without tribal placement

Olexum complanatum Simon Pražák & Lackner, sp. nov.

Body elongate oval, flattened, dorsally convex. Labrum multisetose. Right mandible apically bidentate. Pronotum and elytra with elongate furrows laterally. Scutellar shield invisible. Propygidium almost entirely covered by elytra. Protibia very broad, with a row of denticles on the outer margin and with a prominent apical spur. All tibiae with tarsal grooves.

We name the genus in honour of Aldo Olexa, an excellent Czech specialist of the Histeridae.

Holotype specimen (1408/E), female, Northern Myanmar, inclusion in burmite (ca. 99 Ma), amber piece clear, ca. 11×5×1 mm, with unidentified insect fragments and pieces of debris.

Measurements. Head width: 0.2 mm, width between anterior pronotal angles: 0.23 mm, width between posterior pronotal angles: 0.4 mm, pronotal length: 0.2 mm, elytral length: 0.53 mm, elytral width (across widest point): 0.48 mm. — Body shape elongate oval, flattened, dorsally convex. Head separated from body, located next to the specimen. Cuticle chestnut brown to black. Pronotum with a fairly dense punctuation, punctures (diameter 5 microns) separated approximately by 2 times their diameters. Punctuation of elytra not visible due to white coating covering dorsal surface. Body venter without visible punctuation. Legs light, brown. Female genitalia exposed. — Head almost quadrate, clypeus massive, its length approximately 2/3 of frontal length. Clypeus with irregular sparse prominent setae. Setation of frons not observable. Supraorbital area with a row of regularly separated prominent setae (length 50 microns). Frontal and supraorbital striae indiscernible. Clypeolabral suture well visible. Gular sutures narrowly separated. Labrum short, rectangular, dorsally multisetose, with two pairs of long labral setae located at anterolateral corners, intermingled with shorter sparse setae. Right lateral side of labrum with clearly protruding labral fringe. Right mandible bidentate. Subapical tooth prominent and acute, subparallel with outer mandibular margin. Left mandible and rest of the mouthparts missing. Antennal scape short, thickened, apically truncate with several setae. Pedicel at least 3/4 of scape length, thickened, oval, with individual setae. Antennomeres 3–8 approximately of the same length as scape and pedicel combined. Antennomere 8 significantly wider than antennomeres 3–7. Antennal club slightly longer than antennomeres 3–8, strongly flattened with dense setation. Eyes small, almost completely flattened, almost invisible from dorsal view. — Thorax. Pronotum rectangular, ca. 1.5× wider than long across midline. Lateral stria present, cariniform. Lateral pronotal margin slightly bisinuate, anterior angles rather broadly and obliquely truncate. Pronotal disc asymmetrical (possibly a teratological specimen?). Right lateral area with a single elongate furrow like depression subparallel to the lateral pronotal margin. Left lateral area with two furrow-like depressions, both parallel to the lateral pronotal margin. Single depression at the left anterior angle. Scutellar shield invisible. Elytra longer than wide. Elytral humeri not prominent. Outer lateral margin keel-like, next to it a longitudinal furrow present, reaching approximately 2/3 of elytral length apically. Next to the furrow two faint longitudinal tubercles present medio-apically. Rest of elytral disk without sculpture, elytral suture elevated in apical third. Propygidium almost entirely covered by elytra. Elytral epipleuron with keel-like structures and depressions. Prosternum with a short and broad prosternal lobe with antennal fissures laterally. Basal half of prosternal process between procoxae parallel sided, thence strongly diverging apically. Carinal prosternal stria absent on prosternal apophysis, parallel sided between procoxae, thence strongly diverging anteriorly, concurrent with the prosternal margin. Lateral prosternal stria absent. Antennal cavity present, open anteriorly. Mesoventrite very broad, subtrapezoidal, 4× wider than long. Marginal mesoventral stria faint. Mesoventral disc glabrous. Meso-metaventral suture present. Metaventrite very large and broad, 1.5× wider than long. Marginal metaventral stria absent, postmesocoxal stria faint. Lateral metaventral disc not clearly separated from metaventral disc. Metepisternum fully covered by elytral epipleuron. Lateral disc of metaventrite glabrous. — Abdomen. First visible abdominal ventrite rectangular, glabrous, twice as long as wide, without striae. Rest of the abdomen telescopically inflexed. Propygidium almost entirely covered with elytra. Pygidium short, triangular, bistriate. Female genitalia exposed, apex of valvifers cut off during polishing process. — Legs. Profemur flattened. Protibia strongly dilated, rounded, protibial spur massive; smaller apical spur present underneath it. Outer protibial margin slightly inwardly arcuate in the first anterior forth. Rest of the outer protibial margin round, with regularly separated short denticles, diminishing in size in basal direction, absent in the inwardly arcuate part. Inner protibial margin with a row of setae. Protarsal groove deep, well developed. Terminal protarsomere as long as protarsomeres 1–4 combined. Mesofemur flattened. Outer margin of mesotibia with a row of regularly separated denticles, diminishing in size in posterior direction. Mesotibia with tarsal groove. Mesotarsus with 5 tarsomeres. Mesotarsal claws well developed, longer than half of the terminal mesotarsomere. Metatibia slenderer than mesotibia, curved, with a row of spikes on outer margin sparser than in mesotibia. Metafemur flat. Metatibia with a tarsal groove. Metatarsus with five tarsomeres; tarsomere 5 2.5× longer than 4; metatarsal claws well developed, longer than half of terminal metatarsomere.

Olexum complanatum can be placed within the subfamily Dendrophilinae based on the following characters: prosternal lobe short, with incision for the passage of antenna (Fig. 2F), antennal cavities widely open.

Figure 2. 

Olexum complanatum Simon Pražák & Lackner, gen. & sp. nov. A dorsal view; B ventral view; C head, dorsal view (underlight); D ditto, ventral view (overlight); E ditto, ventral view (fluorescence); F prosternum, mesoventrite (fluorescence); G amber specimen; H protibia; I prosternal process, mesoventrite.

According to the phylogenetic analysis the species is related to the extant genus Dendrophilus Leach, 1817, as well as fossil Dendrophilinae genera Yethiha Caterino, 2021 and Druantia Caterino, 2021 (Fig. 5). Dendrophilinae subfamily is most likely polyphyletic (Zhou et al., 2020) and comprehensive phylogenetic study is desirable. Hence, we refrain from placing O. complanatum into a tribe.

The specific name complanatum refers to the flattened body shape of this species.

Tribe Anapleini Olexa, 1982

Cretanapleus seideli Simon Pražák & Lackner, sp. nov.

Body regularly round, convex with lateral and anterior margins strongly emarginated. Head with a carinate frontal stria. Closed antennal cavity located next to procoxae. Elytra strongly truncate apically, elytral epipleuron with two prominent costae on basal half. Protarsal groove with distinctly elevated margins. Outer protibial margin simple, without teeth or denticles, with a row of simple setae.

The name consists of the prefix cret- referring to the Cretaceous origin of the species, and Anapleus, i.e. the extant genus to which the new genus is similar.

Holotype specimen (1409/E), unknown sex, Northern Myanmar, inclusion in burmite (ca. 99 Ma), amber piece clear, 15×6×2 mm, with small pieces of debris.

Measurements. Head width: 0.14 mm, width between anterior pronotal angles: 0.175 mm, width between posterior pronotal angles: 0.4 mm, pronotal length: 0.21 mm, elytral length: 0.38 mm, elytral width (across widest point): 0.46 mm. — Body regularly round, convex, cuticle brown to black, covered with white debris coating. Body margins dorsally explanate. Elytra with punctures (diameter 10 microns) separated by their diameter. Pronotum with irregular weak longitudinal rugae. — Head. Frontoclypeal area laterally depressed, almost constricted. Frontal stria carinate, widely interrupted medially, slightly continuous to clypeus. Frontal surface laterad of frontal stria forming a depression fit to receive antennal scape in repose, pressed against outer margin of frontal stria. Clypeus anteriorly elevated with large punctures. Labrum dorsally with depressions, with a pair of long prominent setae. Right mandible bidentate with a prominent acute subapical tooth, inner margin of left mandible not visible. Terminal maxillary palpomere elongate, apically acute, slightly flattened. Antennal scape long and robust. Shape of the scape coincident with frontal carina. Pedicel as long as antennomeres 3–6 combined. Antennomeres 3–8 short. Antennal club round, with two apparent straight annuli. Eyes not visible. — Thorax. Pronotal margins narrowing anteriorly; anterior angles acute. Lateral and anterior margins explanate. Median part of frontal disc punctuate, convex with irregular longitudinal rugae. Posterior margin subungulate. Scutellum minute, triangular. Elytra apically truncate. Lateral and basal elytral margins distinctly explanate. Elytral suture elevated. Elytra punctuate at least medially (punctures separated by their diameter); rest of elytral surface covered with debris. Dorsal striation not discernible. Elytral epipleuron unusually wide with two protuberant costae on basal half. Epipleuron largely conceals metepisternum. Prosternal process rectangular, medially depressed. Prosternal lobe short with distinct margin and with antennal fissures laterally. Apex of prosternal lobe keel-like, elevated. Antennal cavity located near procoxa, deep, closed anteriorly. Mesoventrite transverse, 4x wider than long. Meso-metaventral suture invisible. Meso-metaventral stria carinate, anteriorly arcuate. Anterolateral corners with distinct round depressions. Metaventrite with delicate sparse punctures. Lateral metaventral stria complete, carinate. Metaventral disc convex. Metepisternum largely concealed by elytral epipleuron, with rugose punctuation. — Abdomen. First visible abdominal sternite with large punctures separated by their diameter. Pygidium with similarly patterned punctures. Other abdominal segments inflexed and covered with debris, unobservable. — Legs. Profemur with a weakly developed groove for protibial reception. Protibia moderately broad, with a costa along inner margin and slightly thickened along the outer margin, creating a tarsal groove. Outer protibial margin with a dense row of short setae diminishing in size basally, a row of short slender setae also present on the inner margin. Protibial spur tiny. Terminal protarsomere as long as tarsomeres 2–4 combined, claws 1/3 of terminal tarsomere length. Mesotibia slenderer, with a row of short slender setae both on outer and inner margin. Mesotibia with a shallow groove for mesofemoral reception. Mesotarsus similar to protarsus. Metafemur with a groove for metatibial reception, otherwise hind leg identical to middle leg.

Cretanapleus seideli can be clearly placed in the Dendrophilinae based on the prosternum with a short prosternal lobe with antennal fissures laterally. We further place this species in the monophyletic tribe Anapleini (Zhou et al. 2020), as defined by Olexa (1984), based on protibial characters: protarsal groove with distinctly elevated margins, outer protibial margin simple, devoid of teeth or denticles, with a simple row of setae (Fig. 3C, D). However, C. seideli differs from the only extant genus of the tribe, Anapleus Horn, 1873, in several significant characters: presence of frontal stria (absent in Anapleus, Fig. 3G, H), deep and closed antennal cavity (shallow and widely open in Anapleus), and strongly emarginated lateral body margins (Fig. 3G, rounded in Anapleus). Our phylogenetic analyses confirmed the placement of C. seideli in Anapleini (Fig. 5).

Figure 3. 

Cretanapleus seideli Simon Pražák & Lackner, gen. & sp. nov. (A, B, C, E, G) and Anapleus sp. (Turkey; D, F, H; SEM micrographs). A dorsal view; B amber specimen; C–D protibia; E–F ventral view; G–H frontal view.

We dedicate the species to Dr. Matthias Seidel (Naturhistorisches Museum, Vienna, Austria) who introduced the first author of this paper to the study of fossil beetle inclusions.

Without tribal placement

Genus Yethiha Caterino, 2021

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

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.

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.

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).

Figure 4. 

Yethiha pubescens Simon Pražák & 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.

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