Phloiophilus edwardsii

A nationally scarce species, and the only member of its family.

The AIDGAP key to British beetle families came into its own here as this species and family wasn't on my radar at all, and my first guesses as to what family this belonged to were all quickly eliminated (some more qucikly than others!). Using the families key, the broadly flattended sides to the pronotum got me to Phloiophilidae. The unlobed tarsal formula was 5-5-5 and the length of the beetle (excluding antennae) was around 2.3mm. It was found on a wooden fencepost at night.

Phloiophilus edwardsii showing a close-up of its pronotum side, North Elmham Cathedral Meadows (Norfolk, UK), 2nd January 2021