The Protocoleoptera are a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

group of extinct

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

s, containing the earliest and most primitive lineages of beetles. They represented the dominant group of beetles during the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

, but were largely replaced by modern beetle groups during the following

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

. Protocoleopterans typically possess prognathous (horizontal) heads, distinctive

elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...

with regular window punctures,

cuticles A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

with tubercles or scales, as well as a primitive pattern of ventral

sclerite A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...

s, similar to the modern archostematan families

Ommatidae The Ommatidae are a family of beetles in the suborder Archostemata. The Ommatidae are considered the extant beetle family that has most ancestral characteristics. There are only seven extant species, confined to Australia and South America. Howev ...

and

Cupedidae The Cupedidae are a small family of beetles, notable for the square pattern of "windows" on their elytra (hard forewings), which give the family their common name of reticulated beetles. The family consists of about 30 species in 9 genera, with ...

. They are thought to have been

xylophagous Xylophagy is a term used in ecology to describe the habits of an herbivorous animal whose diet consists primarily (often solely) of wood. The word derives from Greek ξυλοφάγος (''xulophagos'') "eating wood", from (') "wood" and (') " ...

and wood boring.

Nomenclature

Protocoleoptera was originally proposed by

Robert John Tillyard Robert "Robin" John Tillyard Fellow of the Royal Society, FRS (31 January 1881 – 13 January 1937) was an English–Australian entomology, entomologist and geologist. Early life and education Tillyard was the son of J. J. Tillyard and his wi ...

in 1924 for the extinct genus '' Protocoleus'', assigned to the family Protocoleidae. ''Protocoleus'' is now considered a member of the extinct order

Protelytroptera Protelytroptera is an extinct order of insects thought to be a stem group from which the modern Dermaptera evolved. These insects, which resemble modern Blattodea, or cockroaches, are known from the Permian of North America, Europe and Australi ...

(a stem-group of the modern

Dermaptera Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forceps-like pincers on their abdomen, and membranous wings folde ...

, the earwigs), which would make Protocoleoptera in this sense a synonym of the order.

Roy Crowson Roy Albert Crowson (22 November 1914 in Hadlow, Kent – 13 May 1999) was an English biologist who specialised in the Taxonomy (biology), taxonomy of beetles. He was curator at the Tunbridge Wells Museum, and then lectured at the Zoology Departm ...

later reused the name "Protocoleoptera" to refer to Early Permian beetles such as the

Tshekardocoleidae Tshekardocoleidae is an extinct family of stem group beetles, known from the Permian. They represent some of the earliest known beetles. They first appeared during the Cisuralian, before becoming extinct at the beginning of the Guadalupian. A clai ...

, 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 . Some authors reject the use of Protocoleoptera and Archecoleoptera and include their members within a broad concept of the suborder

Archostemata The Archostemata are the smallest suborder of beetles, consisting of 50 living species in five families and over 200 described fossil species. They are an ancient lineage with a number of primitive characteristics. Antenna (biology), Antennae may ...

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

is the earliest diverging group among the major families. * Coleoptera ** †'' Coleopsis'' Kirejtshuk et al., 2014 ** †

(Early Permian) ** †

Permocupedidae Permocupedidae is a family of Protocoleopteran stem group beetles. They first appeared during the Early Permian, and were one of the dominant groups of beetles during the Middle Permian. They became rare in the Late Permian, with only one specie ...

(Early Permian–Middle Triassic) ** † Taldycupedidae (Middle–Late Permian) ** †

Ademosynidae Ademosynidae is an extinct family of beetles, known from the Late Triassic to Early Cretaceous. There are at least six genera and 11 species in Ademosynidae. Members of the family were small oval beetles, with a length generally smaller than 1 cm ...

(Late Jurassic–Early Cretaceous) ** † Permosynidae (Permian–Cretaceous, form family?) ** † Rhombocoleidae (Permian–Cretaceous) ** † Triadocupedidae (Triassic) ** † Asiocoleidae (Permian–Jurassic) ** † Peltosynidae (Middle–Late Triassic)

References

Insect suborders Paraphyletic groups {{paleo-beetle-stub