Protocoleoptera

The Protocoleoptera are a paraphyletic group of extinct beetles, containing the earliest and most primitive lineages of beetles. They represented the dominant group of beetles during the Permian, but were largely replaced by modern beetle groups during the following Triassic. Protocoleopterans typically possess prognathous (horizontal) heads, distinctive elytra with regular window punctures, culticles with tubercles or scales, as well as a primitive pattern of ventral sclerites, similar to the modern archostematan families Ommatidae and Cupedidae. They are thought to have been xylophagous and wood boring.

Nomenclature
Protocoleoptera was originally proposed by Robert John Tillyard in 1924 for the extinct genus Protocoleus, assigned to the family Protocoleidae. Protocoleus is now considered a member of the extinct order Protelytroptera (a stem-group of the modern Dermaptera, the earwigs), which would make Protocoleoptera in this sense a synonym of the order. Roy Crowson later reused the name "Protocoleoptera" to refer to Early Permian beetles such as the Tshekardocoleidae, while establishing the Archecoleoptera for Late Permian beetles. Because Protocoleoptera in its original sense is a synonym of Protelytroptera, Cai et al. (2022) proposed a replacement name, Alphacoleoptera Engel, Cai & Tihelka, 2022. Some authors reject the use of Protocoleoptera and Archecoleoptera and include their members within a broad concept of the suborder Archostemata instead.

Taxonomy
The taxonomic naming scheme of early beetles currently has no consensus, with several separate classification schemes proposed for higher level-clades within the stem-group. It is generally agreed that Tshekardocoleidae is the earliest diverging group among the major families.


 * Coleoptera
 * †Coleopsis Kirejtshuk et al., 2014
 * †Tshekardocoleidae Rohdendorf, 1944 (Early Permian)
 * †Permocupedidae Martynov, 1933 (Early Permian–Middle Triassic)
 * †Taldycupedidae Rohdendorf, 1961 (Middle–Late Permian)
 * †Ademosynidae Ponomarenko, 1968 (Late Jurassic–Early Cretaceous)
 * †Permosynidae Tillyard, 1924 (Permian–Cretaceous, form family?)
 * †Rhombocoleidae Rohdendorf, 1961 (Permian–Cretaceous)
 * †Triadocupedidae Ponomarenko, 1966 (Triassic)
 * †Asiocoleidae Rohdendorf, 1961 (Permian–Jurassic)
 * †Peltosynidae Yan, Beutel & Ponomarenko, 2017 (Middle–Late Triassic)