Ceratosuchops inferodios and Riparovenator milnerae Barker, Hone, Naish, Cau, Lockwood, Foster, Clarkin, Schneider & Gostling, 2021 DOI: 10.1038/s41598-021-97870-8 Illustration: Anthony Hutchings Abstract Spinosaurids are among the most distinctive and yet poorly-known of large-bodied theropod dinosaurs, a situation exacerbated by their mostly fragmentary fossil record and competing views regarding their palaeobiology. Here, we report two new Early Cretaceous spinosaurid specimens from the Wessex Formation (Barremian) of the Isle of Wight. Large-scale phylogenetic analyses using parsimony and Bayesian techniques recover the pair in a new clade within Baryonychinae that also includes the hypodigm of the African spinosaurid Suchomimus. Both specimens represent distinct and novel taxa, herein named Ceratosuchops inferodios gen. et sp. nov. and Riparovenator milnerae gen. et sp. nov. A palaeogeographic reconstruction suggests a European origin for Spinosauridae, with at least two dispersal events into Africa. These new finds provide welcome information on poorly sampled areas of spinosaurid anatomy, suggest that sympatry was present and potentially common in baryonychines and spinosaurids as a whole, and contribute to updated palaeobiogeographic reconstructions for the clade. Known material referred to the baryonychines Ceratosuchops inferodios (rear) and Riparovenator milnerae (front) recovered at Chilton Chine (Isle of Wight, UK). White bones represent recovered elements. The arrangement of the elements in the caudal series is estimated; their relative position in the true series, and relationship with respect to each other (bar for those of the largely articulated mid-caudal series), are estimated. Image credit: Dan Folkes (CC-BY 4.0). Scale bar: 100 cm. DINOSAURIA Owen, 1842. THEROPODA Marsh, 1881. TETANURAE Gauthier, 1986. SPINOSAURIDAE Stromer, 1915. BARYONYCHINAE Charig and Milner, 1986, sensu Sereno et al., 1998. CERATOSUCHOPSINI clade nov. Definition: The most inclusive branch-based clade containing Ceratosuchops inferodios but not Baryonyx walkeri and Spinosaurus aegyptiacus. Included taxa: Ceratosuchops inferodios; Riparovenator milnerae; Suchomimus tenerensis Sereno et al., 1998. Diagnosis: postorbital facet of frontal dorsoventrally thick (height more than 40% of length) and excavated by a deep, longitudinal slot; well-defined and strongly curved anterior margins of supratemporal fossa; occipital surface of the basisphenoid collateral oval scars excavated. Genus Ceratosuchops nov. Etymology: kératos (Greek, κέρας)—“horn”, prominent postorbital boss and rugose orbital brow; soûkhos (Greek, Σοῦχος)—“crocodile”; óps (Greek, ὄψ)—“face”. Ceratosuchops inferodios sp. nov. Etymology: īnfernus (Latin)—underworld, hell; erodiós (Greek, ερωδιός)—heron, in reference to its presumed heron-like ecology. Holotype: Associated premaxillary bodies (IWCMS 2014.95.5) and posterior premaxillary fragment (IWCMS 2021.30); a near complete but disarticulated braincase (IWCMS 2014.95.1-3) (Fig. 3). Type locality and type horizon: Wessex Fm. (Barremian), Chilton Chine, near Brighstone (Isle of Wight, UK). Genus Riparovenator gen. nov. Etymology: Rīpārius (Latin)–relating to the riverbank; vēnātor (Latin) –hunter. Riparovenator milnerae sp. nov. Etymology: In honour of Angela Milner and her contributions to spinosaurid palaeobiology (and palaeontology as whole). Holotype: Associated premaxillary bodies (IWCMS 2014.95.6); a disarticulated braincase (IWCMS 2014.96.1, 2; 2020.448.1, 2); a left “preorbital” fragment (partial lacrimal and prefrontal) (IWCMS 2014.96.3) (Fig. 4). Type locality and type horizon: Between the Chilton Chine and Brighstone Sandstones, Wessex Fm. (Barremian), Chilton Chine, near Brighstone (Isle of Wight, UK). Chris T. Barker, David W. E. Hone, Darren Naish, Andrea Cau, Jeremy A. F. Lockwood, Brian Foster, Claire E. Clarkin, Philipp Schneider and Neil J. Gostling. 2021. New Spinosaurids from the Wessex Formation (Early Cretaceous, UK) and the European Origins of Spinosauridae. Scientific Reports. 11: 19340. DOI: 10.1038/s41598-021-97870-8