N. Jb. Geol. Paläont. Abh. Early Access Article Published online January 2025 © 2025 E. Schweizerbart’sche Verlagsbuchhandlung, 70176 Stuttgart, Germany www.schweizerbart.de DOI: 10.1127/njgpa/2025/1235 0077-7749/2025/1235 $ 0.00  1 Introduction This study documents a new finding of an isolated tooth of the hybodontiform shark-like chondrichthyan Strophodus AGASSIZ, 1838 from the Toarcian of the Umbria-Marche-Sabina Domain in the Central Apen- nines (Italy). The oldest occurrence of the clade dates back to the Late Devonian (GINTER et al. 2002; HAIRA- PETIAN & GINTER 2009), and hybodontiforms began among the most successful chondrichthyans during the Triassic and Jurassic but started to decline since the latest Jurassic, eventually going extinct by the end of the Cretaceous (KRIWET & BENTON 2004; REES & UNDERWOOD 2008; KLUG et al. 2010; CAPPETTA 2012; LEUZINGER et al. 2017; UNDERWOOD 2020; STUMPF et al. 2021a, 2021b, 2022). According to several authors, the rapid taxonomic and ecological diversification of elas- mobranchs (i.e., modern sharks, skates, and rays) be- ginning in the late Early Jurassic progressively led to the decline of fully marine Mesozoic hybodontiforms New remain of a hybodontiform shark-like chondrichthyan from the Toarcian of the Central Apennines (Umbria, Italy) Simone Fabbi, Márton Szabó, Peter J. Bonapace, Marco Romano With 5 figures and 1 table Abstract: Herein we report the discovery of an isolated tooth of the hybodontiform shark-like chondrichthyan Strophodus from Toarcian strata near Polino village in the Umbria-Marche-Sabina Domain (UMS) of the Central Apennines of Italy. This discovery contributes to the limited record of Strophodus in the region, which includes only a few specimens from the Toarcian and a partially articulated dentition from the Tithonian. The reconstructed palaeoenvironment, with depths up to 250 m, supported diverse benthic communities, including bivalves, brachiopods, gastropods, and ammonites that likely formed the prey base for durophagous (shell-crushing) predators like Strophodus, indicating a role as a mid-level predator in this ecosystem. Morphological analysis of the tooth suggests it is an anterior element of Strophodus, differing from other recognized species but lacking definitive diagnostic features for specific identification. In addition, alongside recent finds in India, the UMS specimens may represent some of the earliest Gondwanan records of the genus. Keywords: Toarcian; hybodontiform shark-like chondrichthyans; Strophodus; Umbria-Marche- Sabina Domain; Gondwana through a process of competitive displacement (e.g., UNDERWOOD 2006; KRIWET et al. 2009; GUINOT & CAVIN 2016; STUMPF & KRIWET 2019; GUINOT & CAVIN 2020). Regarding post-Jurassic hybodontiforms diversity, the appearance of three palaeobiogeographical provinces (namely Asia, Europe and Africa–South America) around the Tethys led to the maximum diversity of Hybodontiformes at a generic level during the Early Cretaceous (CUNY et al. 2008). Hybodontiforms are traditionally considered as the sister taxon of Elasmobranchii (MAISEY et al. 2004; MAISEY 2012) within the chondrichthyan clade of Eu- selachii (COMPAGNO 1977). Their fossil record mainly consists of teeth, dorsal fin spines, and dermal denti- cles (e.g., STUMPF et al. 2021a), while articulated or dis- articulated skeletons result quite rare (e.g., MAISEY 1982, 1983, 1987; SOLER-GIJÓN et al. 2016; DUFFIN 2010; STUMPF et al. 2021a, 2021b), in large part due to their poorly mineralized cartilaginous endo- skeletons (MAISEY et al. 2020). The skull in male hy- 20250116-104048 A2202/63486/9764C885