Zopheromimini, Alekseev & Nabozhenko, 2023

Alekseev, Vitalii I. & Nabozhenko, Maxim V., 2023, News from Baltic amber: a new tribe of extinct Paleogene ironclad beetles (Coleoptera: Zopheridae: Zopherinae), Zootaxa 5297 (3), pp. 435-445 : 437

Tribe Zopheromimini trib. nov.

Type genus: Zopheromimus gen. nov.

Differential diagnosis. Zopheromimini trib. nov. differ from the other six tribes of Zopherinae by the following combination of features: (1) eyes rounded, lateral, finely facetted, without interfacetal setae; (2) antennomere 2 similar to antennomere 3 in size and shape; (3) prothoracic hypomera without antennal grooves or cavities; (4) antennal cavities on dorsal pronotal surface absent; (5) procoxal cavities externally closed; (6) elytra weakly costate; (7) elytral suture not deflected at apex; (8) all abdominal ventrites similarly articulated; (9) metacoxae separated by a triangular abdominal intercoxal process; (10) abdominal ventrite 5 with paired preapical grooves; (11) body strongly elongate, subcylindrical, densely covered with scale-like setation; (12) antennomeres setose and moniliform, antennal club weakly developed. Zopheromimini trib. nov. share several characters with the extant tribes Latometini (apparently the most similar), Usechini, Monommatini , Phellopsini, Pycnomerini , and Zopherini , but cannot be placed in any of them as they are presently defined. The placement of this new species in a separate, new tribe within Zopherinae is justifiable given the current state of phylogenetic understanding for the family and the striking mixture of diagnostic characters that it shares with members of different tribes.

Zopheromimini trib. nov. share with Latometini rounded eyes, similarly articulated abdominal ventrites, moniliform setose antennomeres, costate elytra, and a triangular intercoxal process of ventrite 1. The newly described tribe can be distinguished from the tribe Latometini ( Ślipiński & Lawrence 1999, Lawrence et al. 2011) in having eyes lacking interfacetal setae, antennomeres 2 and 3 approximately similar in size and shape (pedicel clearly shortened in Latometini ), last palpomere truncate and wider at apex (apical maxillary palpomeres narrowed to acute apex in Latometini ), elytral suture not deflected at apex, and procoxal cavities closed by hypomeral extensions (externally open in Latometini ).

The new tribe shares with Phellopsini paired preapical grooves on abdominal ventrite 5, but differs in having procoxal cavities closed, eyes not transverse and emarginate, intercoxal process of abdominal ventrite 1 not broadly truncate, abdominal ventrites 1–3 not solidly fused, and body length shorter (11–22 mm in Phellopsini ).

Zopheromimini trib. nov. clearly differs from Usechini in the deep anterolateral antennal cavities on the dorsal surface of the pronotum being absent, intercoxal process of abdominal ventrite 1 not being broad and apically arcuate, and abdominal ventrites 1–4 not being fused.

The new tribe can be readily distinguished from Monommatini in the form of eyes (reduced or flat, transverse and subcontiguous dorsally in Monommatini ), body shape (elliptical or ovoid in Monommatini ), procoxal cavities (externally open in Monommatini ), and specifically formed hypomeral antennal cavities being absent (present and unique for Monommatini ).

The tribe Pycnomerini with known representatives in Baltic amber has the last abdominal ventrite without preapical grooves (present in Zopheromimini trib. nov.), and fused abdominal ventrites 1–3 or 1–4 (no ventrites fused in Zopheromimini trib. nov.), which will distinguish them from the representatives of the new tribe. The majority of representatives of Pycnomerini have the dorsal surface glabrous (covered by dense scale-like vestiture in Zopheromimini trib. nov.).

The tribe Zopherini is variable. Zopheromimini trib. nov. differs from the majority of representatives of Zopherini in the following features: prothoracic hypomera lacking grooves (most with antennal grooves in Zopherini ), form of eyes (mostly flattened, transverse, reniform, extending onto dorsal portion of the head in Zopherini ), scutellar shield not being reduced (very small or indistinct in Zopherini ), antenna 11-segmented (with fused last antennomeres resulting in 9- or 10-segments in many Zopherini ), pronotal shape (often with widely rounded posterior angles and narrowed basally in Zopherini ), and prosternal process not being so wide. In addition, representatives of Zopherini have abdominal ventrite 5 with one continuous preapical groove (in contrast with paired preapical grooves in Zopheromimini trib. nov.) and larger body length (9–46 mm).

Composition. The new tribe is proposed for two monotypic extinct genera from Eocene Baltic amber: Zopheromimus gen. nov. and Yantaroxenos Nabozhenko, Kirejtshuk et Merkl, 2016 .