Rove Beetles, Staphylinidae, are considered to be the most specious group of Animals alive today, with 66 928 described species in 35 subfamilies. The group appeared around the beginning of the Jurassic, with the majority of the extant subfamilies having appeared by the end of that period, and with significant ongoing diversification through the Cretaceous. The subfamily Staphylininae contains 9071 described species in 411 genera, making it the third most diverse subfamilies of Rove Beetles, behind the Aleocharinae and Pselaphinae. The Staphylininae is in turn divided into eight extant tribes, the Arrowinini, Coomaniini, Diochini, Maorothiini, Othiini, Platyprosopini, Staphylinini, and Xantholinini, as well as the extinct Thayeralinini. The oldest Staphylinines, Tunicopterus sigara and Subcelytrinus antiquus from the Karatau Formation of Kazakhstan; and Sinostaphylius xiejiajieensis from the Jiuda Formation in China date from the Jurassic, with a further 27 species described from the Cretaceous, and 57 from the Cainozoic.
In a paper published in the Journal of Entomological Science on 4 March 2024, Sandiso Mnguni of the Evolutionary Studies Institute and the Centre of Excellence in Palaeosciences at the University of the Witwatersrand, and Shaw Badenhorst, and Marion Kathleen Bamford, also of the Evolutionary Studies Institute at the University of the Witwatersrand, describe a new species of Staphylinine Beetle from the Cretaceous deposits of the Orapa Diamond Mine in Botswana.
The Opara Diamond mine exploits two diamondiferous kimberlite pipes, (igneous deposits in which material from deep within the Earth is extruded upwards though existing deposits) which cut through Late Cretaceous deposits, reaching the surface and forming a volcanic crater in the Turonian, about 93.1 million years ago. Mining operations here have formed a large oval pit, which, as well as the kimberlite pipes, has exposed a series of lacustrine sediments preserving fossil Plants and Insects.
The new species is placed in the genus Paleothius, which currently contains a single species, Paleothius gracilis from the Early Cretaceous of China, and is given the specific name Paleothius mckayi, in honour of Ian James McKay (1963–2022), who was a palaeoentomologist and Geosciences Outreach Education Specialist at the University of the Witwatersrand, Johannesburg, South Africa, who spent many years describing fossil insects from the Orapa Diamond Mine, and also trained various undergraduate and postgraduate students, including Sandiso Mnguni, who went on to become the first black palaeoentomologist in South Africa.
Paleothius mckayi is a narrow, slender and cylindrical Rove Beetle, measuring 7.70 mm in length (from tip of mandibles to tip of abdomen) and 0.80 mm in width (from exterior edge of left elytron to edge of right elytron). The last abdominal segment is seemingly covered with setae.
Paleothius mckayi is the first fossil Staphylinine Beetle from Africa, and the first from the Southern Hemisphere, with previous Cretaceous Staphylinine Beetles known from China, Myannmar, Russia, and the UK. This makes Botswana a significant extension to the range of the group at this time, though perhaps not a surprising one; the Staphylininae are estimated to have split from their sister group, the Paederinae in the Late Jurassic, about 156.6 million years ago (other estimates put the split between 180 and 145 million years ago), and a Paederine Rove Beetle has previously been discovered from the Orapa deposits.
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