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 297162 10.1093/zoolinnean/zlad165 8e93f8bc-6a2f-4096-8b4f-80c15bb26094 0024-4082 11241243 1EEF0D52-180B-4D3D-AB95-91AF3091E272 Neothalattosuchia , new clade name (PhyloCode) RegNum registration number 1014. Etymology ‘New sea crocodiles’. Neo - from the Ancient Greek (νέος, néos ) for young or new. Thalatto - is from the classical Ancient Greek (θᾰ́λᾰ́ττᾰ́, thálatta ) for sea. Suchus is the Neo-Latinized form of the Greek Soukhos (σοῦΧος), which appears to have been the name of an individual tamed crocodile that lived in Arsinoite nome, in Ancient Egypt ( Larcher 1844: 286 ). The suffix - suchus is today used to refer to crocodiles, crocodylian relatives, or crocodylian analogues. The Neo-Latin suffix - ia denotes an abstract noun of feminine grammatical gender. Geological range Early Jurassic (Hettangian–Sinemurian) to Early Cretaceous (earliest Aptian) ( von Huene and Maubeuge 1952 , 1954 , Gasparini 1985 , Godefroit 1994 , Gasparini et al . 2000 , Chiarenza et al . 2015 , Sachs et al . 2020 , Hicham et al . 2023 ). PhyloCode phylogenetic definition The smallest clade within Thalattosuchia containing Macrospondylus bollensis ( Jäger 1828 ) , Platysuchus multiscrobiculatus ( Berckhemer 1929 ) , Pelagosaurus typus Bronn 1842 and Thalattosuchus superciliosus (Blainville in Eudes-Deslongchamps 1852 ). Reference phylogeny Fig. 3 . PhyloCode diagnostic apomorphies Crocodylomorphs with the following unique combination of characters (6): antorbital cavity much smaller than the orbit in terms of area (173.0) and length (174.0); trigeminal fossa is well developed posteriorly to the fenestra (i.e. fossa very broadly exposed on the quadrate) (438.1); presence of two distinct foramina within the trigeminal fossa (440.1); basioccipital tuberosities are large (459.1); the tibiae are evidently shorter than the femora (with some Toarcian teleosauroid species falling in states 1 and 2) (809.2). Composition Teleosauroidea (which is composed of Machimosauridae and Teleosauridae ) and Metriorhynchoidea (successively comprising of Pelagosaurus , Teleidosaurus , Magyarosuchus , Opisuchus , Eoneustes , Zoneait , and Metriorhynchidae ). Figure 17. Comparative plate of thalattosuchian skulls in lateral view. A, non-neothalattosuchian Plagiophthalmosuchus gracilirostris , paratype NHMUK PV OR 15500; B, the teleosaurid teleosauroid Mystriosaurus laurillardi , referred specimen NHMUK PV OR 14781 (holotype of Steneosaurus brevior ); C, the early diverging metriorhynchoid Pelagosaurus typus , referred specimen NHMUK PV OR 32599; D the metriorhynchid ‘ Metriorhynchus ’ brachyrhynchus , referred specimen NHMUK PV R 3804 (holotype of ‘ Met’. cultridens ). Highlighting that only teleosauroids had dorsolaterally oriented orbits (convergent with extant crocodylians), and that orbit size dramatically increased within Metriorhynchoidea . Figure 18. Comparative plate of extant crocodylian and thalattosuchian internal braincase anatomy. The extant gavialid Gavialis gangeticus , referred specimen UF-herp-118998, in lateral view (A) and in occipital view (B). The non-neothalattosuchian Plagiophthalmosuchus cf. gracilirostris , NHMUK PV OR 33095, in lateral view (C) and in occipital view (D). The early diverging metriorhynchoid Pelagosaurus typus , referred specimen NHMUK PV OR 32599, in lateral view (E) and in occipital view (F). The rhacheosaurin metriorhynchid Cricosaurus araucanensis , holotype MLP 72-IV-7-1, in lateral view (G) and in occipital view (H). All scale bars equal 5 cm. Highlighting the reduction Comments Authorship: This is a new nomen. Prior phylogenetic definition: This clade has never been phylogenetically defined. Content: This clade is what is normally ‘pictured’ as Thalattosuchia —containing the two large radiations Teleosauroidea and Metriorhynchoidea . The chosen specifiers ensure that the major thalattosuchian radiations are represented (e.g. Teleosauridae , Machimosauridae , and Metriorhynchidae ), as well as ‘transitional forms’ such as Pelagosaurus typus . Under this definition, only Turnersuchus hingleyae and Plagiophthalmosuchus gracilirostris ( Fig. 20 ) fall outside of Neothalattosuchia . Prior to our analyses, only Turnersuchus hingleyae from the Pliensbachian had been recovered as an early diverging thalattosuchian ( Wilberg et al . 2023 ). Note: As Neothalattosuchia is above the family-group, only Articles 1–4, 7–10, 11.1–11.3, 14, 27, 28, and 32.5.2.5 of the Zoological Code apply (as per Article 1.2.2).