On the Silurian and lowermost Devonian vertebrates of the Ufa Amphitheatre, the Central Urals, with emphasis on agnathans and correlations with the East Baltic

The vertebrate microremains from the Wenlock (lower Silurian) to the Lower Lochkovian (Lower Devonian) of the Ufa Amphitheatre, on the western slope of the Central Urals, have been studied. This investigation discusses vertebrate taxonomy and biostratigraphy, with an emphasis on the agnathan groups Thelodonti, Heterostraci, Osteostraci, and Anaspida. The thelodont species identified in the region include Paralogania martinssoni (Gross), Phlebolepis elegans Pander, Thelodus laevis (Pander), Thelodus carinatus (Pander), Thelodus parvidens Agassiz, Thelodus sculptilis Gross, Thelodus trilobatus (Hoppe), Turinia pagei (Powrie), Boreania minima Karatajūtė-Talimaa, and Talivalia elongata (Karatajūtė-Talimaa). Representatives of Heterostraci – Eriptychiiformes with Oniscolepis Pander, and Traquairaspidiformes with ‘Traquairaspis’ sp. – are briefly discussed along with recently described cyathaspidid heterostracans (Archegonaspis lindstroemi Kiaer, Archegonaspis integra (Kunth), Cyathaspis alexanderi Märss, and Cyathaspis alexanderi? Märss). Osteostracans comprise Tremataspis schmidti Rohon, Tremataspis rohoni Robertson, Thyestes? sp. ind., Procephalaspis sp. ind., Tahulaspis ordinata Märss, Afanassieva et Blom and Tahulaspis praevia Märss, Afanassieva et Blom, the latter two being assigned to a new family, Tahulaspididae fam. nov. A few birkeniid anaspids (Schidiosteus mustelensis Pander, Septentrionia mucronata? Blom, Märss et Miller, and Liivilepis curvata Blom, Märss et Miller) have also been included to bring together all Silurian and Lower Devonian agnathans of the Ufa Amphitheatre in a single publication. Vertebrate distribution data have been used to determine the age of the strata and correlate the beds with those of the East Baltic. A reversed succession of vertebrate distribution was discovered in a section on the southern bank of Mikhailovsk Pond, and the recurrence of the bonebed complex was detected in the Tabuska Hill section (right bank of the River Ufa).