Archostemata

The Archostemata are the smallest suborder of beetles, consisting of 50 living species in five families and over 200 described fossil species.^[1] They are an ancient lineage with a number of primitive characteristics. Antennae may be thread-shaped (filiform) or like a string of beads (moniliform). This suborder also contains the only beetles where both sexes are paedogenic, Micromalthus debilis. Modern archostematan beetles are considered rare, but were more diverse during the Mesozoic.

Archostemata Temporal range: Late Permian–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Tenomerga mucida
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Suborder:	Archostemata Kolbe, 1908
Families
Crowsoniellidae Cupedidae Jurodidae Micromalthidae Ommatidae

The term "Archostemata" is used more broadly by some authors to include both modern archostematans as well as stem-group beetles like "protocoleopterans", which some modern archostematans closely resemble due to their plesiomorphic morphology.^[2] Genetic research suggests that modern archostematans are a monophyletic group. Some genetic studies have recovered archostematans as the sister group of Myxophaga.^[3]

A 2009 paper argued that the poor diversity of modern Archostemata, compared with the staggering evolutionary success of most other Coleoptera lineages, could be due to the lower efficiency of the thoracic locomotor apparatus, the absence of cryptonephric Malpighian tubules, and competition with other beetles more adapted to angiosperms.^[4]

Taxonomy

There are five extant families.^[5][6]

• Family Crowsoniellidae Iablokoff-Khnzorian, 1983
• Family Cupedidae Laporte, 1838
• Family Jurodidae Ponomarenko, 1985
• Family Micromalthidae Barber, 1913
• Family Ommatidae Sharp and Muir, 1912

Phylogeny

A partial phylogeny of Archostemata and early coleopterans, based on palaeontological data, from Boudinot et al. 2022.^[2]

Coleoptera	Tshekardocoleidae † Mesocoleoptera Permocupedidae † Metacoleoptera Archostemata Cupedidae Ommatidae Micromalthidae Myxophaga Adephaga Polyphaga

According to Li et al. 2023;^[1] archostematan families are in bold.

Coleoptera	Tshekardocoleidae † Permocupedidae † Rhombocoleidae † Triadocupedinae † Ademosynidae † Schizophoridae † Trachypacus Helophorus Torridincola Archostemata Ommatidae Omma Tetraphalerus Jurodidae Sikhotealinia Jurodes † Crowsoniellidae Micromalthidae Catiniidae† Notocupes† Cupedidae Priacma Paracupes Cupes Tenomerga Rhipsideigma Ascioplaga Distocupes

See also

• List of subgroups of the order Coleoptera