Myxophaga is the second-smallest suborder of the

Coleoptera 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 ...

after

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 ...

, consisting of roughly 65 species of small to minute

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 in four families. The members of this suborder are

aquatic Aquatic means relating to water; living in or near water or taking place in water; does not include groundwater, as "aquatic" implies an environment where plants and animals live. Aquatic(s) may also refer to: * Aquatic animal, either vertebrate ...

and

semiaquatic In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...

, and feed on

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

Description

Myxophaga have several diagnostic features: the antennae are more or less distinctly clubbed with usually fewer than nine segments, mesocoxal cavities are open laterally and bordered by a mesepimeron and metanepisternum, the hind wings are rolled apically in the resting positions. Internally, they are characterised by the presence of six

malpighian tubules The Malpighian tubule system is a type of excretory and osmoregulation, osmoregulatory system found in some insects, myriapods, arachnids and tardigrades. It has also been described in some crustacean species, and is likely the same organ as the ...

and the testes are tube-like and coiled. Beetles of this suborder are adapted to feed on algae. Their mouthparts are characteristic in lacking galeae and having a mobile tooth on their left mandible.

Taxonomy

There are four extant families in the suborder Myxophaga divided between two superfamilies, containing about 65 described species, and at least one extinct family. Superfamily

Lepiceroidea ''Lepicerus'' is a genus of myxophagan beetles containing three described species in the family Lepiceridae; it is the only extant genus in the family, with another genus, '' Lepiceratus'' only known from fossils.Jałoszyński, Paweł; Luo, Xiao- ...

Hinton, 1936 *Family

Lepiceridae ''Lepicerus'' is a genus of myxophagan beetles containing three described species in the family Lepiceridae; it is the only extant genus in the family, with another genus, '' Lepiceratus'' only known from fossils.Jałoszyński, Paweł; Luo, Xiao- ...

Hinton, 1936 **''

Lepicerus ''Lepicerus'' is a genus of myxophagan beetles containing three described species in the family Lepiceridae; it is the only extant genus in the family, with another genus, '' Lepiceratus'' only known from fossils.Jałoszyński, Paweł; Luo, Xiao- ...

Motschulsky Victor Ivanovich Motschulsky, sometimes Victor von Motschulsky (Russian: Виктор Иванович Мочульский; 11 April 1810, St. Petersburg – 5 June 1871, Simferopol) was a Russian entomologist mainly interested in beetles. Mo ...

, 1855 **†'' Lepiceratus'' Jałoszyński et al. 2020 Superfamily Sphaeriusoidea

Erichson Wilhelm Ferdinand Erichson (26 November 1809 – 18 December 1848) was a German entomologist and doctor. He was the author of many articles about insects mainly in '' Archiv für Naturgeschichte''. When writing in Latin, he latinised ''Wilhelm'' ...

, 1845 *Family

Hydroscaphidae The Hydroscaphidae are a small family of water beetles known commonly as skiff beetles. As of 2010, there are 23 species in the family. Several are recently described. These beetles are small, most under in length. They are tan to brown in col ...

LeConte, 1874 ** ''

Hydroscapha ''Hydroscapha'' is a genus of beetles endemic to Europe and the United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic ...

'' LeConte, 1874 ** ''

Scaphydra ''Scaphydra'' is a genus of beetles in the family Hydroscaphidae The Hydroscaphidae are a small family of water beetles known commonly as skiff beetles. As of 2010, there are 23 species in the family. Several are recently described. These be ...

'' Reichardt, 1973 ** ''

Yara Yara may refer to: People * Yara (given name) * Yara (surname), a Japanese surname * Yara (Angolan footballer), Yara Lukenia F. da Costa Lima () * Yara (Brazilian footballer), Yara Silva (born 1964) * Yara (singer), Lebanese pop singer Carl ...

'' Reichardt & Hinton, 1976 **''

Confossa ''Confossa'' is a genus of water beetle in the family Hydroscaphidae The Hydroscaphidae are a small family of water beetles known commonly as skiff beetles. As of 2010, there are 23 species in the family. Several are recently described. These ...

'' Short, Joly, García & Maddison, 2015 *Family

Sphaeriusidae Myxophaga is the second-smallest suborder of the Coleoptera after Archostemata, consisting of roughly 65 species of small to minute beetles in four families. The members of this suborder are aquatic and semiaquatic, and feed on algae. Descriptio ...

, 1845 **''

Sphaerius ''Sphaerius'' is a genus of beetles in the family Sphaeriusidae, comprising 18 extant species. It is one of the two extant genera in the family, the other being '' Bezesporum''. They are typically found along the edges of streams and rivers, whe ...

'' Waltl, 1838 **'' Bezesporum'' Fikáček et al. 2022 **†'' Burmasporum'' Kirejtshuk 2009 **†'' Crowsonaerius'' Li & Cai in Li et al. 2023 *Family

Torridincolidae The Torridincolidae are a small family of beetles in the suborder Myxophaga. It contains these genera:Steffan, 1964 ** '' Claudiella'' Reichardt & Vanin, 1976 ** ''

Delevea ''Delevea'' is a genus of beetles in the family Torridincolidae The Torridincolidae are a small family of beetles in the suborder Myxophaga. It contains these genera:Iapir'' Py-Daniel, da Fonseca & Barbosa, 1993 ** '' Incoltorrida'' Steffan, 1973 ** ''

Satonius ''Satonius'' is a genus of beetles in the family Torridincolidae. It is native to East Asia. The type species, ''S. kurosawai'', was originally described as a species of ''Delevea''. Several other species have been described since. References< ...

'' Endrödy-Younga, 1997 ** '' Torridincola'' Steffan, 1964 ** '' Ytu'' Reichardt, 1973 Family †

Triamyxidae ''Triamyxa'' is an extinct genus of myxophagan beetle in the monotypic family Triamyxidae from the Carnian stage of Late Triassic, approximately 230 million years ago. It was found in the Keuper Claystone of Poland. The type species is ''Tr ...

Qvarnström et al. 2021 *†''

Triamyxa ''Triamyxa'' is an extinct genus of myxophagan beetle in the monotypic family Triamyxidae from the Carnian stage of Late Triassic, approximately 230 million years ago. It was found in the Keuper Claystone of Poland. The type species is ''Tri ...

'' Qvarnström et al. 2021 Unplaced in family *†'' Leehermania'' Chatzimanolis et al. 2012

Distribution

Living members of Lepiceridae are confined to northern South America and Central America. Members of Sphaeriusidae occur on all continents except Antarctica, while Hydroscaphidae occurs on all continents except Australia and Antarctica. Torridincolidae occurs in Africa, Asia, and South America.

Fossil record

The fossil record of myxophagan beetles is sparse, likely due to their small size limiting

preservation potential Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov ...

. The currently oldest myxophagan is ''

,'' described in 2021 from numerous specimens of found in a

coprolite A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name ...

found in Late Triassic (late

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227.3 ...

, around 232-227 million years ago) aged sediments in Poland. It was placed in its own monotypic family Triamyxidae, and was resolved as either the most basal myxophagan or sister to Hydroscaphidae. The next oldest is '' Leehermania'' from the Late Triassic (

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

)

Cow Branch Formation The Cow Branch Formation is a Late Triassic geologic Formation (geology), formation in Virginia and North Carolina in the eastern United States. The formation consists of Cyclostratigraphy, cyclical beds of black and grey Lacustrine deposits, lacus ...

of North Carolina, which had previously been interpreted as the oldest known

rove beetle The rove beetles are a family (biology), family (Staphylinidae) of beetles, primarily distinguished by their short elytra (wing covers) that typically leave more than half of their abdominal segments exposed. With over 66,000 species in thousand ...

but in 2019 was reinterpreted as an early diverging relative of the family Hydroscaphidae. A fossil impression assigned to the living genus ''

'' in Hydroscaphidae is known from the

Yixian Formation The Yixian Formation (; formerly Romanization of Chinese, transcribed as Yihsien Formation or Yixiang Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the Barremian stage of the Early Cretaceous. I ...

in the

Jehol Biota The Jehol Biota includes all the living organisms – the ecosystem – of northeastern China between 133 and 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. These d ...

, dating from the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

). Fossils from the early Late Cretaceous (

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

) aged

Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...

from Myanmar, have been assigned to the extant genus ''

'' and extinct genus '' Lepiceratus'' within Lepiceridae,Jałoszyński, Paweł; Luo, Xiao-Zhu; Hammel, Jörg U.; Yamamoto, Shûhei & Beutel, Rolf G. (2020). "The mid-Cretaceous †''Lepiceratus'' gen. nov. and the evolution of the relict beetle family Lepiceridae (Insecta: Coleoptera: Myxophaga)". ''Journal of Systematic Palaeontology''. 18 (13). as well as the extant ''

'' and '' Bezesporum'' and the extinct '' Burmasporum'' and '' Crowsonaerius'', belonging to Sphaerusidae.

Gallery

Notes

References

External links

* * {{DEFAULTSORT:Myxophaga Insect suborders Beetles described in 1955 Beetles of North America Beetles of Asia