New Brachiopods and Conodonts from the Qarari Unit (upper Kungurian, Ne Oman): Implications for Biostratigraphy from a Palaeobiodiversity Hotspot

During a fieldwork campaign conducted in February 2023 in the Batain Plain, NE Oman, nearly 1800 brachiopod specimens of extremely diverse fauna have been collected from four localities belonging to the Permian Qarari Unit, along with rock samples for conodont study. Previous age determinations based on fusulines and conodonts suggested a late Kungurian-early Roadian age, also supported by the brachiopods stratigraphic range. The systematic study of the collected material is currently in progress, but so far, eighteen new genera occurrences have been identified, adding to the already high richness (68 species of 52 genera) of the brachiopod fauna. Most of the newly recorded genera are productids, confirming the dominance of this order based on previous data. These newly identified occurrences are species of Neochonetes (Zhongyingia) Shen & Archbold, 2001, Bibatiola Grant, 1976, Reticulatia Muir-Wood & Cooper, 1960, Stereochia Grant 1976, Cimmeriella Archbold & Hogeboom, 2000, Chonosteges Muir-Wood & Cooper, 1960 and Leptodus Kayser, 1883, all supported by the occurrence of several specimens each. Specimens close to the American genus Peniculauris Muir-Wood & Cooper, 1960 are also present, possibly representing a new taxon. The genus Paralyttonia Wanner in Wanner & Sieverts, 1935 has also been recorded as a brachiopod epizoozoan. Other interesting occurrences are specimens belonging to a species of the North American genus Rallacosta Cooper & Grant, 1976or of an allied genus, as well as specimens close to the genus Heteraria Cooper & Grant, 1976, while the newly recorded genera from the Tethyan realm are Pontisia Cooper & Grant, 1969, TomiopsisBenediktova, 1956, Elivella Fredericks, 1924, Astegosia Cooper & Grant, 1969, Hemiptychina Waagen, 1882, Omanilasma Angiolini et al., 2006 and Bisolcatelasma Crippa & Angiolini, 2012. The palaeobiogeographic affinities of the brachiopods of the Qarari Unit are interesting: previous studies indicated the Kungurian brachiopod fauna of Karakoram to be the closest, albeit showing a much lower diversity. In terms of generic richness, the Qarari Unit has been compared to the faunas of South China, Irrawaddy block of Myanmar and the Rat Buri Limestone of South Thailand, although the brachiopod composition of these is quite different. With the addition of the new records, the closest is the Rat Buri Limestone, with around 35% of the genera shared with the Qarari Unit. Regarding the age of the Qarari Unit, these new brachiopod occurrences are in agreement with the previous age assignment of a late Kungurian-early Roadian age, especially given the newly recorded occurrences of Astegosia, Hemiptychina, Omanilasma and Bisolcatelasma. These genera also occur in the Wordian of Oman, North Iran and Southern Thailand suggestive of a younger age of the Qarari Unit. On the other hand, new preliminary data on conodonts from these localities suggest a late Kungurian age based on the occurrence of Hindeodus cf. excavatus, Sweetognathus subsymmetricus, and Mesogondolella siciliensis sensu lato based on comparisons with South China. These taxa may extend into the Roadian. This would not be in conflict with the brachiopod ranges, even if some typical Guadalupian genera should in this case occur earlier than previously thought.