Myxophaga

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 and the testes are tube-like and coiled.{{cite encyclopedia|title=Band 4 Part 38: Arthropoda, Hälfte: Insecta, Coleoptera, Beetles|encyclopedia=Handbuch der Zoologie/Handbook of Zoology|publisher=Walter de Gruyter|date=2005|volume=1|isbn=3-11-017130-9|last2=Leschen|first2=R.|last1=Beutel|first1=R.|chapter=Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim)}}

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.{{harvnb|Beutel|Leschen|2005|page=43}}

There are four extant families in the suborder Myxophaga divided between two superfamilies,{{cite web |url=http://tolweb.org/Myxophaga/8871 |title=Myxophaga |publisher=Tree of Life Web Project |date=2007 |access-date=2017-05-26}} containing about 65 described species,{{Cite journal |last=Mesaros |first=Gabor |title=Sphaeriusidae (Coleoptera, Myxophaga): A new beetle family to the fauna of Serbia |url=http://scindeks.ceon.rs/Article.aspx?artid=1820-95211306071M |journal=Bulletin of the Natural History Museum |issue=6 |pages=71–74 |doi=10.5937/bnhmb1306071m|year=2013 |doi-access=free }} and at least one extinct family.{{efn|† Denotes that the group is extinct}}

Superfamily Lepiceroidea Hinton, 1936

• Family Lepiceridae Hinton, 1936
• Lepicerus Motschulsky, 1855
• †Lepiceratus Jałoszyński et al. 2020

Superfamily Sphaeriusoidea Erichson, 1845

• Family Hydroscaphidae LeConte, 1874
• Hydroscapha LeConte, 1874
• Scaphydra Reichardt, 1973
• Yara Reichardt & Hinton, 1976
• Confossa Short, Joly, García & Maddison, 2015
• Family Sphaeriusidae Erichson, 1845
• Sphaerius Waltl, 1838
• Bezesporum Fikáček et al. 2022
• †Burmasporum Kirejtshuk 2009
• †Crowsonaerius Li & Cai in Li et al. 2023
• Family Torridincolidae Steffan, 1964
• Claudiella Reichardt & Vanin, 1976
• Delevea Reichardt, 1976
• Iapir Py-Daniel, da Fonseca & Barbosa, 1993
• Incoltorrida Steffan, 1973
• Satonius Endrödy-Younga, 1997
• Torridincola Steffan, 1964
• Ytu Reichardt, 1973

Family †Triamyxidae Qvarnström et al. 2021

• †Triamyxa Qvarnström et al. 2021

Unplaced in family

• †Leehermania Chatzimanolis et al. 2012

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.{{Citation|last1=Sampaio|first1=Brunno H.L.|title=Families Hydroscaphidae and Torridincolidae|date=2018|url=https://linkinghub.elsevier.com/retrieve/pii/B9780128042236000226|work=Thorp and Covich's Freshwater Invertebrates|pages=519–525|publisher=Elsevier|language=en|doi=10.1016/b978-0-12-804223-6.00022-6|isbn=978-0-12-804223-6|access-date=2021-07-26|last2=Short|first2=Andrew E.Z.|url-access=subscription}}

The fossil record of myxophagan beetles is sparse, likely due to their small size limiting preservation potential.{{Cite journal |last1=Fikáček |first1=Martin |last2=Beutel |first2=Rolf G. |last3=Cai |first3=Chenyang |last4=Lawrence |first4=John F. |last5=Newton |first5=Alfred F. |last6=Solodovnikov |first6=Alexey |last7=Ślipiński |first7=Adam |last8=Thayer |first8=Margaret K. |last9=Yamamoto |first9=Shûhei |date=January 2020 |title=Reliable placement of beetle fossils via phylogenetic analyses – Triassic Leehermania as a case study (Staphylinidae or Myxophaga?) |url=https://onlinelibrary.wiley.com/doi/10.1111/syen.12386 |journal=Systematic Entomology |language=en |volume=45 |issue=1 |pages=175–187 |doi=10.1111/syen.12386 |bibcode=2020SysEn..45..175F |s2cid=203407211 |issn=0307-6970|url-access=subscription }} The currently oldest myxophagan is Triamyxa, described in 2021 from numerous specimens of found in a coprolite found in Late Triassic (late Carnian, 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.{{Cite journal |last1=Qvarnström |first1=Martin |last2=Fikáček |first2=Martin |last3=Vikberg Wernström |first3=Joel |last4=Huld |first4=Sigrid |last5=Beutel |first5=Rolf G. |last6=Arriaga-Varela |first6=Emmanuel |last7=Ahlberg |first7=Per E. |last8=Niedźwiedzki |first8=Grzegorz |date=June 2021 |title=Exceptionally preserved beetles in a Triassic coprolite of putative dinosauriform origin |journal=Current Biology |volume=31 |issue=15 |language=en |pages=3374–3381.e5 |doi=10.1016/j.cub.2021.05.015 |pmid=34197727 |doi-access=free|bibcode=2021CBio...31E3374Q }} The next oldest is Leehermania from the Late Triassic (Norian) Cow Branch Formation of North Carolina, which had previously been interpreted as the oldest known rove beetle but in 2019 was reinterpreted as an early diverging relative of the family Hydroscaphidae. A fossil impression assigned to the living genus Hydroscapha in Hydroscaphidae is known from the Yixian Formation in the Jehol Biota, dating from the Early Cretaceous (Aptian).{{cite journal |author1=Cai, C. |author2=Short, A. E. Z. |author3=Huang, D. |date=2012 |title=The First Skiff Beetle (Coleoptera: Myxophaga: Hydroscaphidae) from Early Cretaceous Jehol Biota |journal=Journal of Paleontology |volume=86 |issue=1 |pages=116–9 |doi=10.1666/11-050.1 |bibcode=2012JPal...86..116C |s2cid=140170420}} Fossils from the early Late Cretaceous (Cenomanian) aged Burmese amber from Myanmar, have been assigned to the extant genus Lepicerus and extinct genus Lepiceratus within Lepiceridae,{{cite journal |author1=Kirejtshuk, A. G. |author2=Poinar, G. |date=2006 |title=Haplochelidae, a new family of cretaceous beetles (Coleoptera: Myxophaga) from Burmese amber |journal=Proceedings of the Entomological Society of Washington |volume=108 |pages=155–164}}{{cite journal |author1=Ge, S. Q. |author2=Friedrich, F. |author3=Beutel, R. G. |date=2010 |title=On the systematic position and taxonomic rank of the extinct myxophagan dagger Haplochelus (Coleoptera) |url=http://booksandjournals.brillonline.com/content/journals/10.1163/187631210x537385 |journal=Insect Systematics and Evolution |volume=41 |issue=4 |pages=329–338 |doi=10.1163/187631210X537385|url-access=subscription }}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). {{doi|10.1080/14772019.2020.1747561}} as well as the extant Sphaerius and Bezesporum and the extinct Burmasporum and Crowsonaerius, belonging to Sphaerusidae.{{cite journal |author1=Kirejtshuk, A. G. |date=2009 |title=A new genus and species of Sphaeriusidae (Coleoptera, Myxophaga) from Lower Cretaceous Burmese amber |url=http://www.zobodat.at/stable/pdf/DENISIA_0026_0099-0102.pdf |journal=Denisia |volume=26 |pages=99–102}}{{Cite journal |last1=Li |first1=Yan-Da |last2=Ślipiński |first2=Adam |last3=Huang |first3=Di-Ying |last4=Cai |first4=Chen-Yang |date=2023-01-11 |title=New fossils of Sphaeriusidae from mid-Cretaceous Burmese amber revealed by confocal microscopy (Coleoptera: Myxophaga) |journal=Frontiers in Earth Science |volume=10 |pages=901573 |doi=10.3389/feart.2022.901573 |issn=2296-6463|doi-access=free |bibcode=2023FrEaS..10.1573L }}{{Cite journal |last1=Fikáček |first1=Martin |last2=Yamamoto |first2=Shûhei |last3=Matsumoto |first3=Keita |last4=Beutel |first4=Rolf G. |last5=Maddison |first5=David R. |date=2022-12-07 |title=Phylogeny and systematics of Sphaeriusidae (Coleoptera: Myxophaga): minute living fossils with underestimated past and present-day diversity |url=https://onlinelibrary.wiley.com/doi/10.1111/syen.12571 |journal=Systematic Entomology |volume=48 |issue=2 |language=en |pages=233–249 |doi=10.1111/syen.12571 |s2cid=254440169 |issn=0307-6970|url-access=subscription }}

{{gallery|Sphaerius minutus (10.3897-zookeys.808.30600) Figures 1–9 (cropped).jpg|Specimen of Sphaerius minutus (Sphaeriusidae) in various views|Hydroscapha natans01.jpg|Specimens of Hydroscapha natans (Hydroscaphidae)|Lepicerus_inaequalis.jpg|Specimen of Lepicerus inaequalis (Lepiceridae)|||||||||width=300|height=180|align=center}}

• List of subgroups of the order Coleoptera

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• {{cite web |title=Myxophaga |work=Atlas of Living Australia |url=https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:3717c802-bced-437f-b3da-94087e7ac12c}}
• {{Wikispecies-inline|Myxophaga}}

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Category:Insect suborders

Category:Beetles described in 1955

Category:Beetles of North America

Category:Beetles of Asia