Wikipedia
The Archostemata are the smallest suborder of beetles, consisting of fewer than 50 known species organized into five families. They are an ancient lineage with a number of primitive characteristics. They are similar in morphology to the first beetles, which appear in the fossil record about 250 million years ago. Antennae may be thread-shaped (filiform) or like a string of beads (or moniliform). This suborder also contains the only paedogenic beetles, Micromalthus debilis.
These beetles are considered rare. Fossil deposits from the Permian suggest that the Archostemata were once much more common and dispersed over a wide portion of the globe, and the species that remain are but scattered vestiges of their former population. Today, five families remain worldwide ( Crowsoniellidae, Cupedidae, Jurodidae, Micromalthidae, and Ommatidae), with only two (Cupedidae and Micromalthidae) occurring in North America.