Burmapseudomorphus planus gen. et sp. nov. - a Late Cretaceous stem group member of the specialized Pseudomorphini (Carabidae, Coleoptera) from northern Myanmar

A new adephagan beetle embedded in Burmese amber from northern Myanmar is described as Burmapseudomorphus planus gen. et sp. nov. From its broad and flat habitus, the lack of a pronoto-elytral angle, the short and broad head, the short mesoventrite, and the lancet-shaped elongate prosternal process it resembles beetles belonging to the aquatic Dytiscoidea. The metacoxal plates are similar to those of Noteridae. However, pubescent antennal flagellomeres, an anisochaetous protibial antenna cleaner, transversely oriented metepimera, and metacoxae not reaching beyond the lateral margin of the metaventrite identify the fossil as an atypical species of Carabidae. Externally closed procoxal cavities, lacking procoxal rests of the mesoventrite, a narrow mesepimeron not reaching the mesocoxal cavity, and lobate metepimera indicate a placement in a clade comprising Harpalinae and Brachininae. This is supported by analyses of morphological data and a Hennigian character evaluation. The short and transverse head, the streamlined body without pronoto-elytral angle, and the secondarily elongated prosternal process suggest a placement as stem group member of the specialized Pseudomorphini. In contrast to species of the crown group of this lineage, a distinct submento-mental suture is present, ventral cephalic antennal grooves are missing, and the elytra are not truncated posteriorly. The fossil is the first record for Pseudomorphini and documents an origin of this specialized group of Carabidae at least dating back to the Cretaceous. A superficial similarity with the extant migadopine genus Stichonotus (e.g. broad and oval body, apically pointed prosternal process) is the result of convergence.