Omma

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.^[1] 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.^[2] 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.^[2]

Omma Temporal range: Rhaetian–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Omma stanleyi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Family:	Ommatidae
Genus:	Omma Newman, 1839
Type species
Omma stanleyi Newman, 1839
Synonyms
Procarabus Oppenheim, 1888 Chalepocarabus Handlirsch, 1906 Pyrochroophana Handlirsch, 1906 Ommamima Ponomarenko, 1964  ?Cionocups Kirejtshuk, 2020

Description

According to Li, Huang & Cai, 2021, Omma is distinguished from other ommatid beetles by the following characters:^[1]

Head without prominent posterior protuberances. Labrum with dentate anterior margin. Separate mentum absent. Anterior third of gulamentum not depressed. Pronotal disc with rounded lateral edges; dorsal surface without ridges or protuberances. Sternopleural suture absent. Prosternal process short. Punctured explanate elytral epipleura absent. CuA of hind wings forked; wedge cell present. Abdominal ventrites abutting.

• 
  Holotype (A,B) and paratype (C,D) specimens of Omma liassicum dating to the Triassic-Jurassic boundary ~ 200 million years ago
• 
  Holotype specimen of Omma janetae from the Mid-Cretaceous Burmese amber of Myanmar, dating to around 100 million years ago
• 
  Specimen of Omma forte from the Mid-Cretaceous Burmese amber of Myanmar

Species, temporal and spatial distribution

The following extinct and extant species have been described.^[3][4][5]

Taxa labelled (?) are considered questionable by Kirejtshuk, 2020

Omma stanleyi Newman, 1839 (type), recent, Australia

Fossil species

• Middle-Late Jurassic, Jiulongshan Formation and Tiaojishan Formation, Inner Mongolia, China,
  • Omma ancistrodontum (Tan, Wang, Ren & Yang, 2012) = Pareuryomma ancistrodontum (Callovian-Oxfordian), Daohugou Village, Shantou Township, Ningcheng County, Inner Mongolia, China
  • (?)Omma daxishanense Cai & Huang, 2017 Upper Jurassic (Oxfordian), China
  • Omma delicatum Tan, Wang, Ren & Yang, 2012
• Late Jurassic (Oxfordian and Kimmeridgian) Karabastau Formation, Karatau, Kazakhstan
  • Omma aberratum Ponomarenko, 1968
  • (?)Omma grande (Ponomarenko, 1964) = Tetraphalerus grandis
  • Omma jurassicum Ponomarenko, 1968
  • Omma pilosum (Ponomarenko, 1964) = Ommamima pilosum
• Upper Jurassic (Tithonian), Solnhofen Limestone, Bavaria, Germany
  • Omma brevipes (Deichmueller, 1886) = Pyrochroa brevipes
  • (?)Omma zitteli (Oppenheim, 1888) = Procarabus zitteli
• Lower Cretaceous (Aptian), Dzun-Bain Formation, Bon-Tsagan, Mongolia
  • (?)Omma antennatum Ponomarenko, 1997
  • Omma longicolle (Ponomarenko, 1997) = Tetraphalerus longicollis
• Mid Cretaceous (Albian-Cenomanian) Burmese amber, Myanmar
  • Omma davidbatteni Jarzembowski et al., 2020
  • Omma forte Li, Huang & Cai, 2021
  • Omma janetae Kirejtshuk, 2020
  • Omma lii Jarzembowski, Wang & Zheng, 2016
  • Omma manukyani (Kirejtshuk, 2020) formerly placed in separate genus Cionocups.^[1]
  • Omma (Coronomma) axsmithi Jarzembowski, Zheng & Zhao, 2022^[6]
• Other Species:
• (?)Omma altajense Ponomarenko, 1997, Middle to Late Jurassic, Togo-Khuduk Formation, Bakhar, Mongolia
• Omma avus Ponomarenko, 1969, Lower Jurassic (Hettangian), Dzhil Formation, Issyk-Kul’, Kyrgyzstan
• (?)Omma elongatum (Brodie, 1845) = Carabus elongatus, Lower Cretaceous (Berriasian), Purbeck Group Lower Cretaceous (Hauterivian), Weald Clay, United Kingdom
• (?)Omma gobiense Ponomarenko, 1997, Upper Jurassic (Tithonian), Ulan-Ereg Formation, Khoutiin-Khotgor, Mongolia
• Omma liassicum Crowson, 1962, Late Triassic (Rhaetian), Lilstock Formation, Brown's wood, Warwickshire, Lower Jurassic (Hettangian), Blue Lias, Binton, Warwickshire, Lower Jurassic (Sinemurian), Charmouth Mudstone, Charmouth, England
• Omma sibiricum Ponomarenko, 1966, Lower Cretaceous (Valanginian), Zaza Formation, Baissa, West Transbaikalia Russia

References

1. Li, Yan-Da; Huang, Di-Ying; Cai, Chen-Yang (2021-11-30). "New species of Omma Newman from mid-Cretaceous Burmese amber (Coleoptera, Archostemata, Ommatidae)". Deutsche Entomologische Zeitschrift. 68 (2): 341–348. doi:10.3897/dez.68.74174. ISSN 1860-1324. S2CID 244783528.
2. Escalona, Hermes E.; Lawrence, John F.; Ślipiński, Adam (2020-01-24). "The extant species of the genus Omma Newman and description of Beutelius gen. nov. (Coleoptera: Archostemata: Ommatidae: Ommatinae)". Zootaxa. 4728 (4): 547–574. doi:10.11646/zootaxa.4728.4.11. ISSN 1175-5334. PMID 32229891. S2CID 212766123.
3. Ommatidae Species List Archived 2012-10-23 at the Wayback Machine at Joel Hallan’s Biology Catalog. Texas A&M University. Retrieved on 11 May 2012.
4. Tan, Jingjing; Wang, Yongjie; Ren, Dong; Yang, Xingke (2012). "New fossil species of ommatids (Coleoptera: Archostemata) from the Middle Mesozoic of China illuminating the phylogeny of Ommatidae". BMC Evolutionary Biology. 12: 113. doi:10.1186/1471-2148-12-113. PMC 3518168. PMID 22776212.
5. Kirejtshuk, Alexander G. (2020-02-17). "Taxonomic Review of Fossil Coleopterous Families (Insecta, Coleoptera). Suborder Archostemata: Superfamilies Coleopseoidea and Cupedoidea". Geosciences. 10 (2): 73. Bibcode:2020Geosc..10...73K. doi:10.3390/geosciences10020073. ISSN 2076-3263.
6. Jarzembowski, Edmund A.; Zheng, Daran; Zhao, Xianye (2021-11-12). "Is the beetle Omma (Insecta: Coleoptera) a living fossil?". Geological Society, London, Special Publications. 521: SP521–2021–56. doi:10.1144/SP521-2021-56. ISSN 0305-8719. S2CID 244091355.