The history, systematics, and nomenclature of Thalattosuchia (Archosauria: Crocodylomorpha) Author Young, Mark T. School of GeoSciences, Grant Institute, The King’s Buildings, University of Edinburgh, James Hutton Road, Edinburgh, EH 9 3 FE, United Kingdom & LWL-Museum für Naturkunde, Sentruper Strasse 285, 48161 Münster, Germany marktyoung1984@gmail.com Author Wilberg, Eric W. Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794, USA Author Johnson, Michela M. Staatliches Museum für Naturkunde, Rosenstein 1, 70191 Stuttgart, Germany Author Herrera, Yanina Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), División Paleontología Vertebrados, Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, B 1900 La Plata, Buenos Aires, Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) & Departamento de Diversidade e Ecologia, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga 6681, Prédio 12, Porto Alegre, 90619 - 900, Brazil & Setor de Paleontologia, Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga 6681, Prédio 40, Porto Alegre, 90619 - 900, Brazil Author Brandalise, Marco de Andrade Departamento de Diversidade e Ecologia, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga 6681, Prédio 12, Porto Alegre, 90619 - 900, Brazil & Setor de Paleontologia, Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga 6681, Prédio 40, Porto Alegre, 90619 - 900, Brazil Author Brignon, Arnaud 5, Villa Jeanne-d’Arc, 92340 Bourg-la-Reine, France Author Sachs, Sven Naturkunde-Museum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602 Bielefeld, Germany Author Abel, Pascal Eberhard-Karls-University Tübingen, Fachbereich Geowissenschaften, Sigwartstrasse 10, 72074 Tübingen, Germany Author Foffa, Davide Department of Geosciences, Virginia Tech, 4044 Derring Hall 926 West Campus Drive, Blacksburg 24061, Virginia, USA & School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B 15 2 TT, United Kingdom Author Fernández, Marta S. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), División Paleontología Vertebrados, Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, B 1900 La Plata, Buenos Aires, Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Author Vignaud, Patrick Laboratoire de Paléontologie, Evolution, Paléoécosystèmes et Paléoprimatologie, CNRS UMR 7262, Department of Geosciences, University of Poitiers, 86073 Poitiers Cedex 9, France Author Cowgill, Thomas School of GeoSciences, Grant Institute, The King’s Buildings, University of Edinburgh, James Hutton Road, Edinburgh, EH 9 3 FE, United Kingdom Author Brusatte, Stephen L. School of GeoSciences, Grant Institute, The King’s Buildings, University of Edinburgh, James Hutton Road, Edinburgh, EH 9 3 FE, United Kingdom text Zoological Journal of the Linnean Society 2024 2024-01-09 200 2 547 617 http://dx.doi.org/10.1093/zoolinnean/zlad165 journal article 10.1093/zoolinnean/zlad165 0024-4082 11241243 1EEF0D52-180B-4D3D-AB95-91AF3091E272 Rhacheosaurini Young et al . 2011a (Zoological Code) Rhacheosaurini Young et al . 2011a: 914 , converted clade name (PhyloCode) RegNum registration number 1019. Type genus: Rhacheosaurus von Meyer, 1831 . Etymology ‘Pertaining to Rhacheosaurus ’. The stem Rhacheosaur - is based on the genus Rhacheosaurus . - ini is a Latin masculine plural suffix for ‘pertaining to’. Under Article 29.2 of the Zoological Code, the suffix - ini denotes a tribe rank within the family-group. Geological range Late Jurassic (late Kimmeridgian) to Early Cretaceous (early Valanginian) ( Young et al . 2010 , Sachs et al . 2020 ). PhyloCode phylogenetic definition The largest clade within Metriorhynchidae containing Rhacheosaurus gracilis von Meyer, 1831 , but not Metriorhynchus brevirostris ( Holl 1829 ) , and Gracilineustes leedsi ( Andrews 1913 ) . Reference phylogeny Fig. 3 . Zoological Code diagnosis and PhyloCode diagnostic apomorphies Metriorhynchid crocodylomorphs with the following unique combination of characters (5): external nares oriented dorsally (shared with derived members of the ‘E’-clade) (95. 2); posterodorsal retraction of the posterior margin of the narial fossa (shared with the ‘E’-clade) (104.3–6); external nares have a fully ossified internarial premaxillary bar (105.2); absence of a constriction at the premaxilla–maxilla suture (shared with the ‘E’-clade, Plesiosuchus and Dakosaurus ) (114.0); one-third or less of total premaxilla length is posterior to the external nares (127.3). Potentially diagnostic characters The following four characters may be diagnostic for Rhacheosaurini , however, at present we do not know if they could be more widely distributed within Metriorhynchinae or more restricted to the Rhacheosaurus + Cricosaurus subclade. Only the discovery of more complete specimens within Rhacheosaurini , and non-rhacheosaurin metriorhynchines will answer this: 25 presacral vertebrae (686.1); increase in the number of caudal vertebrae, such that there are 50 or more (713.1); humerus proximal region confined to the proximal surface (753.0); humerus diaphysis contributes less than 25% of total humerus length (758.2). The character: anterior margin of the frontoparietal fossae (in dorsal view) terminates level to the postorbital anterior margin, or anterior to it (192.2), is equivocal due to the instability within Metriorhynchinae , and which taxa fall within Rhacheosaurini . Figure 26. Comparative plate of metriorhynchid skulls in dorsal view. A, the early diverging Thalattosuchus superciliosus , lectotype MNHN.F RJN 256; B, the rhacheosaurin Cricosaurus araucanensis , holotype MLP 72-IV-7-1; C, the dakosaurin Dakosaurus andiniensis , referred specimen MOZ-PV 6146. All scale bars equal 10 cm. Composition Rhacheosaurus , Cricosaurus , and multiple taxa that do not have a valid generic assignment (e.g. ‘ Metriorhynchus ’ palpebrosus , ‘ Cricosaurus ’ saltillensis , and the Cretaceous rhacheosaurin). Comments Authorship: The nomen Rhacheosaurini was first used by Young et al . (2011). Figure 27. Comparative plate of metriorhynchid skulls in lateral view. A, the rhacheosaurin Cricosaurus suevicus , lectotype SMNS 9808; B, the early diverging Thalattosuchus superciliosus , lectotype MNHN.F RJN 256; C, the dakosaurin Dakosaurus maximus , neotype SMNS 8203. All scale bars equal 10 cm. Prior phylogenetic definition: Young et al. (2011a) defined Rhacheosaurini as the most inclusive clade, including Rhacheosaurus gracilis von Meyer, 1831 but not Metriorhynchus geoffroyii von Meyer, 1832 , and Gracilineustes leedsi ( Andrews 1913 ) .