Durnonovariaodus maiseyi gen. et sp. nov., a new hybodontiform shark-like chondrichthyan from the Upper Jurassic Kimmeridge Clay Formation of England Sebastian Stumpf 1 , Steve Etches 2 , Charlie J. Underwood 3 and Jürgen Kriwet 1 1 Department of Palaeontology, University of Vienna, Vienna, Austria 2 Museum of Jurassic Marine Life, Kimmeridge, Dorset, United Kingdom 3 School of Earth and Planetary Sciences, Birkbeck College, University of London, London, United Kingdom ABSTRACT A partial skeleton of a hybodontiform shark-like chondrichthyan from the Upper Jurassic Kimmeridge Clay Formation of Dorset, England, is described and designated as a new genus and species, Durnonovariaodus maiseyi gen. et sp. nov. The holotype and only known specimen, which is represented by disarticulated splanchnocranial elements with associated teeth, a single dorsal fin spine, the pelvic girdle, as well as unidentifiable cartilage fragments, plus countless dermal denticles, exhibits a puzzling combination of dental and skeletal features, providing important new insights into the morphological and ecological diversity of hybodontiforms. Durnonovariaodus gen. nov. displays a unique set of dental characters, showing close morphological resemblance to Secarodus from the Middle Jurassic of England, which was erected for distinctive, strongly labio-lingually compressed multicuspid cutting teeth originally described as Hybodus polyprion. Skeletally, Durnonovariaodus gen. nov. resembles Hybodus and Egertonodus in having a palatoquadrate with a palatobasal process and an ethmoidal articular surface, combined with the possession of dorsal fin spines ornamented with costae. Therefore, and given the absence of any conclusive phylogenetic framework, Durnonovariaodus maiseyi gen. et sp. nov. is here tentatively referred to Hybodontidae until more complete material becomes available in order to enable a more reliable suprageneric identification. The holotype of Durnonovariaodus maiseyi gen. et sp. nov. contains two separate pelvic half-girdles, a feature previously considered as evolutionarily primitive among hybodontiforms. However, unfused pelvic half-girdles also occur in the supposedly closely related species Hybodus hauffianus and may in fact have been more widely distributed among hybodontiforms than previously thought, thus rendering the phylogenetic utility of separated pelvic half-girdles for inferring hybodontiform interrelationships difficult and unresolved. How to cite this article Stumpf S, Etches S, Underwood CJ, Kriwet J. 2021. Durnonovariaodus maiseyi gen. et sp. nov., a new hybodontiform shark-like chondrichthyan from the Upper Jurassic Kimmeridge Clay Formation of England. PeerJ 9:e11362 DOI 10.7717/peerj.11362 Submitted 24 February 2021 Accepted 6 April 2021 Published 11 May 2021 Corresponding author Sebastian Stumpf, sebastian.stumpf@univie.ac.at Academic editor Andrew Farke Additional Information and Declarations can be found on page 22 DOI 10.7717/peerj.11362 Copyright 2021 Stumpf et al. Distributed under Creative Commons CC-BY 4.0