Ceratonotha danica, Lyubarsky & Vasilenko & Perkovsky, 2024

Lyubarsky, G. Yu., Vasilenko, D. V. & Perkovsky, E. E., 2024, Ceratonotha, a new erotylid genus (Coleoptera, Erotylidae) from late Eocene amber, Zootaxa 5458 (2), pp. 275-285 : 277-281

Ceratonotha danica sp. nov.

Figures 1–3

Type material. Holotype. NHMD 153515, “ A. K. Andersen 27-3-1968 ”, Danish amber, late Eocene.

Etymology. Named for the country of origin.

Description. Body elongate-oval, not strongly subcylindrical; weakly convex in dorsal aspect, apparently glabrous dorsally; widest at midlength of elytra; unicolorous from dark-brown to black, elytra immaculate ( Fig. 1A ). Total body length 3.5 mm, maximum body width 1.5 mm; pronotal length 0.7 mm, maximum pronotal width 1.15 mm; elytral length 2.3 mm; ratio pronotal length/elytral length (PL/EL) = 0.3.

Head. Head robust, weakly convex in dorsal aspect, rather long (from anterior margin of clypeus to posterior margin of compound eyes), about two thirds of pronotal length, dorsal surface slightly convex. Clypeus convex, truncate apically. Compound eye globular with black facets, bordered dorsally with long supraocular line which is not extending towards anterior eye margin. Facets fine, about 10–11 facets in longitudinal axis of eye; a row of 3–4 facets equal to length of antennomere two; interfacetal setae present, shorter than facetal diameter. Post-ocular ridge indistinct, nearly absent ( Fig. 3A ). Short setae along anterior and lateral margins and around eyes. Dorsal interocular distance to head width ratio 0.72. Frons slightly convex. Vertex, transverse occipital ridge (vertexal line) and stridulatory files not discernible in the holotype since posterior portion of head is retracted into pronotum. Punctures of dorsal head rather dense (distance between punctures equal to 1.0–1.5× their diameter), becoming fine and sparse towards clypeus; punctures on clypeus becoming finer and sparser toward apical margin where they disappear. Antennae with 11 antennomeres, club with three antennomeres; relatively short and stout, extending towards base of pronotum, covered by small setiferous punctures. Scape and pedicel cylindrical; antennomere 3 about one third longer than antennomere 4; antennomeres 5–7 slightly conical; antennomere 8 slightly transverse; antennomeres 9–10 transverse; terminal antennomere rounded apically, asymmetrical. Relative length ratios of antennomeres 1–11: 8.5:7:7:5.5:5:6:6:6:8:7:10 ( Fig. 1B , 3A ).

Thorax. Pronotum evenly convex in dorsal aspect, strongly transverse (length to width ratio 0.6), widest slightly ahead of midlength; with narrow posterolateral longitudinal sulcus located half distance between midlength and lateral margin, sulci as long as one-sixth pronotal length ( Fig. 2B , 3B ). Anterior margin truncate, anterolateral angle not projecting, rounded, medially not beaded. Pronotal dorsum strongly shagreened. Lateral margins slightly rounded, with wide border; anterior margin not bordered at middle; posterior margin bisinuate. Posterolateral angles nearly rectangular. Pronotal punctation fine and sparse, distance between punctures equal to 2–3× their diameters. Length of prosternum equal to longitudinal eye length. Prosternum laterally strongly punctured, short setose; with several small carinae. Prosternal process not visible due to the structure of the amber. Procoxal cavities not visible due to the structure of the amber. Mesoventrite moderately sparsely punctate with punctures of various sizes, with short to moderately long setae. Metaventrite slightly convex in ventral aspect, with large, sparse punctures, distance between punctures equal to 2–4× their diameters.

Scutellar shield distinctly transverse, pentagonal with rounded angles, twice wider than long; scutellar surface very finely punctured. Hind wings not visible.

Elytra elongate elliptical, widest at anterior one third, about 1.7× as long as combined width, 3.4× as long as pronotum; with marginal bead at base (with only weak rudiment of it present on humeral area). Elytral punctures coarse (larger than those on pronotum) and dense, arranged into non-impressed striae on elytral disc, confused apically. Interstriae flat, each with row of extremely fine secondary punctures. Elytral setae fine, short, shorter than intervening spaces between punctures in rows ( Fig. 1A ), noticeable only on elytral apex. Epipleura well developed, complete, extending towards elytral apex.

Legs short and slender, tarsi with 5 tarsomeres, not lobate. All coxae distinctly separated, pro- and mesocoxae semiglobular, metacoxae transverse, elongate-elliptical. Coxae, femora and tibiae finely and densely punctate. Femora rather robust, compressed laterally. Tibiae gradually dilated to apex, with apical fringe of short and narrow spinules, and two short terminal spurs. Tarsomeres 1–4 cylindrical; subequal in length, tarsomere 4 one third shorter than tarsomere 3. Metatarsomere 1 about one third longer than wide. Tarsomeres 1–3 not lobed beneath, pubescent ventrally with long, fine, dense, posteriad-directed setae. Metatarsomere 5 about as long as combined length of tarsomeres 2–4 (12:14).

Abdomen. With five visible, similarly articulated ventrites ( Fig. 2A ); covered with fine setigerous punctures, distance between punctures 1.5–3.0 times their diameters. Subcoxal lines in ventrite 1 not visible. Relative length (medially, including intercoxal process) ratios of ventrites 1–5: 26:17:17:17:13. Last visible abdominal sternite short. Abdominal apex with triangular ventral impression.

Remarks. A notably shortened fourth tarsomere compared to the third tarsomere is considered a stable character in extant basal erotylids. As stated by Yoshida & Leschen (2020, p. 274): “Among the more basal erotylids, only the xenosceline genus Zavaljus Reitter and Australonotha do not have a strongly reduced tarsomere 4.” A long fourth tarsomere is shared with other fossil erotylids presently placed in the Xenoscelinae and may simply represent a plesiomorphic state for all Erotylidae . Further phylogenetic work is needed to resolve the distinction and placement of extant and extinct members of the Xenoscelinae and Pharaxonothinae .

Ceratonotha danica sp. nov. differs from the only known representative of its subfamily found in amber, Cycadophila mumia ( Alekseev & Bukejs, 2017) , in the combination of the following characters: anterior pronotal border disconnected medially the comparatively smaller body (3.5 mm versus 3.6–3.8 mm); the rather long head (from the anterior margin of the clypeus towards the line connecting the posterior margins of the eyes), approximately two thirds of the pronotal length; the antennomere three about one third longer than the next antennomere; the pronotal anterior margin weakly curved, not sinuate near the eye; the strongly shagreened pronotum; the pronotal sulci as long as one sixth of the pronotal length (versus one fourth in Cycadophila mumia ); the uniformly dark-brown to black body (versus uniformly ochraceous). The last abdominal ventrite is just a little longer than the penultimate one.

As far as can be seen, the fourth tarsomere in C. mumia is slightly shorter compared to the third tarsomere. The same applies to the specimen No 578–1 [CCHH] ( Alekseev and Bukejs 2017). However, antennomeres of the flagellum in the specimen No 578-1 (which was considered partially destroyed and deformed) appear elongate, slenderer than those in Ceratonotha danica , and the tarsomeres are more strongly setose. Otherwise, in all generic level characters, Cycadophila mumia and specimen No 578-1 [CCHH] ( Alekseev and Bukejs 2017) from Baltic amber are members of the genus Ceratonotha as defined above. Based on this, C. mumia is here transferred into Ceratonotha , becoming Ceratonotha mumia (Alekseev and Bukejs) , new combination.

The genus Ceratozamia is currently most species-rich in the Mesoamerican region. In addition, the most earlydiverging lineage of cycad-associated erotylid pharaxonothine beetles in the Americas is confined to the genus Ceratozamia ( Tang et al. 2018) . Interestingly, the majority of European Cenozoic cycad records belong to the Zamiaceae —two species of Ceratozamia ( Kvaček & Manchester 1999; Kvaček 2014; Coiro et al. 2023). With extant Ceratozamia requiring a beetle pollinator, the logical conclusion is that extinct European Ceratozamia were also pollinated by erotylids. It is possible that a member of Ceratonotha was associated with cycads and possibly even a pollinator.

To better understand the relationships of Ceratonotha with extant cycad pollinating erotylid genera, it would be highly desirable to study male genitalia. Extant cycad associated genera of Pharaxonothinae each have unique modifications to the male genitalia. In Ceratophila the aedeagus and tegmen are laterally compressed—a shape typical for Erotylidae , not twisted but positioned upside down. In Cycadophila they are twisted like a corkscrew and positioned laterally in the abdomen when at rest. While in Pharaxonotha , the male genitalia are also positioned upside down, but are dorso-ventrally flattened unlike other Erotylidae ( Tang et al. 2020 and references therein). These shapes and orientations are interpreted by Tang et al. (2020) as possible adaptations for mating in the tight confines typically found in male cycad cones.

Figures

FIGURE 1. Photo: 1A. Body, dorsal view; 1B. Head and pronotum (frontal view).

FIGURE 2. Photo: 2A. Ventral view. 2B. Head and pronotum (dorsal view).

FIGURE 3. Photo: 3A. Head, dorsally. 3B. Habitus illustration.