Abstract

Variegated mud-loving beetles, or Heteroceridae, are a small family belonging to the polyphagan superfamily Byrrhoidea. To date, only two poorly preserved compression fossils have been known from the Early Cretaceous of Eurasia. Here we describe the first heterocerid beetles in mid-Cretaceous amber from northern Myanmar, Excavotarsus lini gen. et sp. nov. and Ex. minor sp. nov.. The two new fossil species are distinguished from all extant heterocerids by their elongate body shape, apical 8–9 antennomeres forming a loose serrate club, pronotum longer than wide, protibia lacking robust spines, and two-segmented protarsi. This peculiar combination of plesiomorphic and derived characters suggests that Excavotarsus represents an early-diverging lineage of Heteroceridae and indicates that the family originated and diversified before the mid-Cretaceous.