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.
Description According to Li, Huang & Cai, 2021, Omma is distinguished from other ommatid beetles by the following characters:
Species The following extinct and extant species have been described.Ommatidae Species List at Joel Hallan’s Biology Catalog. Texas A&M University. Retrieved on 11 May 2012. 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. Omma (Coronomma) axsmithi Jarzembowski, Zheng & Zhao, 2022 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
References