“…The most basal and oldest hybodontiform sharks known from complete, unambiguous skeletal remains are Tristychius and Onychoselache from the Viséan (early Carboniferous), part of the early Carboniferous chondrichthyan radiation (Friedman and Sallan, 2012). However, isolated teeth of general hybodontiform morphology (Ginter et al, 2002) date back further, to the Famennian (Late Devonian), indicating that hybodontiform sharks might have evolved and radiated prior to the end-Devonian mass extinction event (Duffin, 2001; Coates and Gess, 2007). Early Carboniferous holomorphic hybodontiform fossils occur in near-coastal and lagoonal to even freshwater deposits, indicating that hybodontiforms might have evolved in shallow-marine environments; it appears that they were euryhaline early in their evolutionary history, being able to tolerate different salinity regimes (e.g., Duffin, 1997; Duffin and Thies, 1997; Rees and Underwood, 2006, 2008; Klug et al, 2010; Leuzinger et al, 2015, 2017; Stumpf and Kriwet, 2019; Stumpf et al, 2021a).…”