First record of the somniosid shark Protoxynotus misburgensis from the Santonian (Late Cretaceous) of the Southern Tethyan Realm

The previously known occurrences of Protoxynotus were stratigraphically disjunct with the first occurrence in the Turonian being separated by a gap of about 6 Myr from the Campanian occurrences. The new record of isolated teeth from the Late Santonian of Lebanon described in this study narrows this gap down to about 3 Myr with a hiatus spanning the Coniacian. Although the famous Lebanese Konservat-Lagerstatten are well known for its exquisitely preserved articulated elasmobranch specimens, previous studies paid little attention to recover isolated teeth exclusively found by acid processing of rock samples. In this study, we present for the first time isolated teeth, which were extracted from about two kilograms of rock matrix by acid processing. This study highlights the importance and potential of acid processing even of small sample sizes for unlocking the stratigraphic and palaeogeographic occurrence of elasmobranchs through time, providing essential data for global diversity analyses of this group. Furthermore, this study documents the first record of Protoxynotus in the southern Tethyan Realm and pointing towards the occupation of overlapping or similar habitats of the deep-water somniosids Protoxynotus and Cretascymnus during the Late Cretaceous.