Arceotermes Engel & Jiang, 2021

JIANG, RI-XIN, ZHANG, HONG-RUI, ELDREDGE, K. TARO, SONG, XIAO-BIN, LI, YAN-DA, TIHELKA, ERIK, HUANG, DI-YING, WANG, SHUO, ENGEL, MICHAEL S. & CAI, CHEN-YANG, 2021, Further evidence of Cretaceous termitophily: Description of new termite hosts of the trichopseniine Cretotrichopsenius (Coleoptera: Staphylinidae), with emendations to the classification of lower termites (Isoptera), Palaeoentomology 4 (4), pp. 374-389 : 381

Arceotermes Engel & Jiang , gen. nov.

Type species. Arceotermes hospitis Engel & Jiang , sp. nov.

Etymology. The new genus-group name is a combination of the Latin terms arceo (meaning, to “hinder” or “guard”) and termes (“termite”; genitive, termitis). The gender of the name is masculine.

Diagnosis. Total body length (as preserved) 5.00 mm, head length (excluding mandibles) 2.08 mm, maximum width 1.83 mm. Like most soldier termites, the head is large and longer than broad, although the posterior temples are not tumid (tumid in Archotermopsis Desneux, 1904b ) and the head is not dorsoventrally compressed (compressed in Stolotermitidae ). The lateral surface of the head lacks striations (present in Archotermopsis ), and the lateral margins are largely parallel. The dorsal surface of the head lacks a clearly visible Y-shaped ecdysial cleavage scar (it is difficult, though, to determine whether it is absent or merely exceedingly faint), lacks a fontanelle, and lacks ocelli. The compound eyes are absent and the antenna is composed of 17, largely moniliform articles. Mandibles are large, elongate, and gently bent ventrad toward their apices, with prominent apical and marginal teeth. Like Archotermopsidae and Hodotermitidae , the soldier mandibles have two right marginal teeth and three left marginal teeth (in addition to the apical tooth), the right marginal teeth are broad, much like that of Archotermopsis , and simple (sometimes with two points, such as in Hodotermopsis Holmgren, 1911 ( Hodotermopsinae Engel , subfam. nov., vide infra), Zootermopsis laticeps ( Banks, 1906) , and to a lesser degree like Microhodotermes Sjöstedt, 1926 ). The apical teeth are long, pointed, and curved. The postmentum is greatly broadened anteriorly, with concave lateral margins tapering posteriorly. The pronotum is broad (not massive and elongate as in Ginormotermes Engel et al., 2016 ), and about as wide as the head, with the anterior margin broadly concave and the lateral margins faintly convex, roughly parallel, and broadly rounded posteriorly to a broadly and weakly convex posterior margin. The surface of the pronotum is flat.The tibial spur formula is 3-3-? (metatarsi not preserved in holotype), and the tarsi are tetramerous, while the pretarsus lacks an arolium. Unfortunately, the abdominal apex is damaged in the holotype of the type species and the cerci are not preserved.

The genus differs from soldiers of Krishnatermes and Ginormotermes by the tetramerous tarsi (pentamerous in those genera), and from Cosmotermes Zhao et al., 2020 by the absence of compound eyes, the long left first marginal tooth relative to the second marginal tooth, and the broader pronotum (distinctly narrower than head in Cosmotermes ).