Omma Explained

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.

Description

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

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, recent, Australia

Fossil species

• Middle-Late Jurassic, Jiulongshan Formation and Tiaojishan Formation, Inner Mongolia, China,
  • Omma ancistrodontum (Callovian-Oxfordian), Daohugou Village, Shantou Township, Ningcheng County, Inner Mongolia, China
  • (?)Omma daxishanense Upper Jurassic (Oxfordian), China
  • Omma delicatum
• Late Jurassic (Oxfordian and Kimmeridgian) Karabastau Formation, Karatau, Kazakhstan
  • Omma aberratum
  • (?)Omma grande
  • Omma jurassicum
  • Omma pilosum
• Upper Jurassic (Tithonian), Solnhofen Limestone, Bavaria, Germany
  • Omma brevipes
  • (?)Omma zitteli
• Lower Cretaceous (Aptian), Dzun-Bain Formation, Bon-Tsagan, Mongolia
  • (?)Omma antennatum
  • Omma longicolle
• Mid Cretaceous (Albian-Cenomanian) Burmese amber, Myanmar
  • Omma davidbatteni
  • Omma forte Li, Huang & Cai, 2021
  • Omma janetae
  • Omma lii
  • Omma manukyani (Kirejtshuk, 2020) formerly placed in separate genus Cionocups.^[1]
  • Omma (Coronomma) axsmithi Jarzembowski, Zheng & Zhao, 2022^[6]
• Other Species:
• (?)Omma altajense, Middle to Late Jurassic, Togo-Khuduk Formation, Bakhar, Mongolia
• Omma avus, Lower Jurassic (Hettangian), Dzhil Formation, Issyk-Kul’, Kyrgyzstan
• (?)Omma elongatum, Lower Cretaceous (Berriasian), Purbeck Group Lower Cretaceous (Hauterivian), Weald Clay, United Kingdom
• (?)Omma gobiense, Upper Jurassic (Tithonian), Ulan-Ereg Formation, Khoutiin-Khotgor, Mongolia
• Omma liassicum, 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, Lower Cretaceous (Valanginian), Zaza Formation, Baissa, West Transbaikalia Russia

Notes and 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. en. 68. 2. 341–348. 10.3897/dez.68.74174. 244783528. 1860-1324. free.
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. 10.11646/zootaxa.4728.4.11. 32229891. 212766123. 1175-5334.
3. http://insects.tamu.edu/research/collection/hallan/Arthropoda/Insects/Coleoptera/Family/Ommatidae.txt Ommatidae Species List
4. Jingjing. Tan. Yongjie. Wang. Dong. Ren. Xingke. Yang. 2012. New fossil species of ommatids (Coleoptera: Archostemata) from the Middle Mesozoic of China illuminating the phylogeny of Ommatidae. BMC Evolutionary Biology. 12. 113. 10.1186/1471-2148-12-113. 22776212. 3518168. free.
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. 10.3390/geosciences10020073. 2020Geosc..10...73K. 2076-3263. free.
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. en. SP521–2021–56. 10.1144/SP521-2021-56. 244091355. 0305-8719.