Microvertebrate remains from the early Eocene of SW Sardinia (Italy): preliminary note

During the Eocene, the Sardinian area was populated by a rich and diverse continental fauna. The vertebrate fossil record of Sardinia includes mammals, reptiles, and freshwater fish (Zoboli et al., 2023). In this preliminary note, we describe new Eocene microvertebrate remains from the Lignitifero Formation (Ypresian-early Lutetian) outcropping at Tanca Aru (Vallermosa, SW Sardinia, Italy). The Eocene outcrop of this locality is represented by a succession of continental deposits, interpreted as alluvial plain sediments. The microvertebrate fossils were collected in a bioclastic lacustrine limestone approximately 8 cm thick. The limestone samples were treated in the laboratory in a 10% solution of acetic acid. Several fossil remains have been identified, including seven teeth of freshwater fish of the Characiformes group, three teeth of the Cyprinidae group, and several indeterminate fragments of reptiles (teeth and mandible fragments). Three teeth of the Characiformes group are provisionally classified as cf. Alestoides sp.; these teeth are divided by morphology into two anterior teeth from the inner row of the premaxilla, and one lateral tooth from the external row of the dentary. Two teeth of the Characiformes group are instead classified as cf. Hydrocynus sp. Two teeth of Cyprinidae have been interpreted as pharyngeal teeth. These new preliminary data increase our knowledge of the biodiversity of Sardinia during the Eocene, providing helpful information for a greater understanding of the palaeoecology and palaeobiogeography of SW Europe during the Paleogene.