The Cupedidae are a small family of beetles, notable for the square pattern of "windows" on their elytra, which give the family their common name of reticulated beetles.
The Archostemata are the smallest suborder of beetles, consisting 45 living species in five families. 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. 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 to due to their plesiomorphic morphology. Genetic research suggests that modern archostematans are a monophyletic group. Some genetic studies have recovered archostematans as the sister group of Myxophaga.
The Trachypachidae are a family of beetles that generally resemble small ground beetles, but that are distinguished by the large coxae of their rearmost legs. There are only six known extant species in the family, with four species of Trachypachus found in northern Eurasia and northern North America, and two species of Systolosoma in Chile and Argentina. They were much more diverse in the past, with dozens of described species from the Mesozoic.
Blapsium is an extinct genus of beetles from the Middle Jurassic of England. The only described species is B. egertoni, which is known from a single specimen found by the Earl of Enniskillen at the Taynton Limestone Formation, also known as the Stonesfield Slate. The specimen is deposited in the Natural History Museum, London. It is incompletely preserved, lacking a head, pronotum and legs. It has a broad, convex body. It has a very short metathorax, which may suggest that it was apterous.
Coptoclavidae is an extinct family of aquatic beetles in the suborder Adephaga. The Coptoclavidae lived from the Late Triassic to the Early Cretaceous. Coptoclavidae is a member of the adephagan clade Dytiscoidea, which contains other aquatic beetles. Suggested reasons for their extinction to include the rise of teleost fish, or competition with Gyrinidae and Dytiscidae, which possess defensive secretions and sucking channels in the mandibles of larvae, which coptoclavids likely lacked. It has been suggested that the genus Timarchopsis and the subfamily Timarchopsinae are only distantly related to other coptoclavids based on cladistic analysis, with Timarchopsis being more closely related to geadephagans like carabids and trachypachids instead. Another study also suggested similarly for Coptoclavisca and possibly other coptoclaviscines.
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. However, the geographical distribution was much wider during the Mesozoic spanning across Eurasia and Australia, suggesting that they were widespread on Pangea. So far, over 26 extinct genera containing over 170 species of these beetles have been described. Three extant genera have been assigned to this family: Omma,Tetraphalerus and Beutelius. The family is considered to be a subfamily of Cupedidae by some authors, but have been found to be more closely related to Micromalthidae in molecular phylogenies. A close relationship with Micromalthidae is supported by several morphological characters, including those of the mandibles and male genitalia. Due to their rarity, their ecology is obscure, it is likely that their larvae feed on deadwood.
The Madygen Formation is a Late Triassic (Carnian) geologic formation and Lagerstätte in the Batken and Osh Regions of western Kyrgyzstan, with minor outcrops in neighboring Tajikistan and Uzbekistan. The conglomerates, sandstones and mudstones of the 560 m (1,840 ft) thick formation were deposited in terrestrial lacustrine, alluvial, fluvial and deltaic environments.
Rhabdocupes is an extinct genus of beetles in the family Ommatidae, known from the Late Triassic Madygen Formation of Kyrgyzstan, containing the following species:
Zygadenia is an extinct genus of archostematan beetles from the Jurassic to Cretaceous. It is considered to be a senior synonym of Notocupes by Kirejtshuk (2020), but other researchers suggest to reserve the genus Zygadenia as a form taxon for isolated elytra that probably belong to the genus Notocupes, while retaining Notocupes as a valid genus for complete body fossils.
Omma is a genus of beetles in the family Ommatidae. Omma is an example of a living fossil. The oldest species known, O. liassicum, lived during the final stage of the Triassic (Rhaetian), over 200 million years ago, though the placement of this species in Omma has been questioned. Numerous other fossil species are known from the Jurassic and Cretaceous of Europe and Asia. The only living species is Omma stanleyi, which is endemic to Australia. Three other extant species endemic to Australia that were formerly part of this genus were moved to the separate genus Beutelius in 2020.Omma stanleyi is strongly associated with wood, being found under Eucalyptus bark and exhibiting thanatosis when disturbed. Its larval stage and many other life details are unknown due to its rarity. Males are typically 14–20 mm in length, while females are 14.4-27.5 mm. Omma stanleyi occurs throughout eastern Australia from Victoria to Central Queensland.
The Hassberge Formation is a geologic formation in Bavaria, Germany. It preserves fossils dating back to the Carnian stage of the Triassic period.
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.
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 species known from the Triassic, Frankencupes ultimus from the Middle Triassic (Anisian) Röt Formation of Germany. They are thought to have been xylophagous, which is presumed to be the ancestral ecology of beetles.
Liadytidae is an extinct family of adephagan beetles. There are at least two genera and about seven described species in Liadytidae. They are known from the Early Jurassic to Early Cretaceous of Asia. They are members of the clade Dytiscoidea, and like other members of that group were adapted for aquatic life.
Liadytiscinae is a subfamily of extinct predaceous diving beetles in the family Dytiscidae. There are about 5 genera and 10 described species in Liadytiscinae. All currently known members of the subfamily are known from the Early Cretaceous Jehol Biota of China.
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. Characteristics of the family include a pronotum without anterior angles and a rounded anterior margin, and elytra with 9–12 punctate striae. The systematic position of the family within the order Coleoptera is currently uncertain: they can be considered early examples of the suborder Polyphaga, or unusual examples of Archostemata.
Tshekardocoleidae is an extinct family of beetles, known from the Permian. They represent amongst the oldest beetles. Like other primitive beetles, they are thought to have been xylophagous. They first appeared during the Cisuralian, before becoming extinct at the beginning of the Guadalupian. A claimed Jurassic record is doubtful. The oldest known beetle, Coleopsis, was originally assigned to this family, but is now assigned to its own family Coleopsidae.
Taldycupedidae is an extinct family of beetles primarily known from the Permian period.
Notocupes is an extinct genus of medium-sized archostematan beetles from the Mesozoic Era of Eurasia, including over 50 described species. Historically, the genus was classified as a member of the family Ommatidae, but the presence of characters such as the horizontal mandibular cutting edge, separated procoxae and overlapping abdominal sternites indicate that the genus may have a closer affinity with the family Cupedidae. Notocupes is considered to be a junior synonym of Zygadenia by Kirejtshuk (2020), but other researchers suggest to reserve the genus Zygadenia as a form taxon for isolated elytra that probably belong to the genus Notocupes, while retaining Notocupes as a valid genus for complete body fossils. Most species of Notocupes were described from compression fossils. An additional three species were described from Cenomanian-aged Burmese amber, which were treated as a separate genus, Echinocups, by Kirejtshuk (2020), but Li et al. (2023) consider Echinocups to be a junior synonym of Notocupes. Notocupes has a flattened body, which may suggest that it occupied narrow habitats, such as living under bark. Some species had serrated/spined margins of the carapace, which may have served as a defense against predators, or served as camouflage to resemble bark.
