The history, systematics, and nomenclature of Thalattosuchia (Archosauria: Crocodylomorpha) Young, Mark T. Wilberg, Eric W. Johnson, Michela M. Herrera, Yanina Brandalise, Marco de Andrade Brignon, Arnaud Sachs, Sven Abel, Pascal Foffa, Davide Fernández, Marta S. Vignaud, Patrick Cowgill, Thomas Brusatte, Stephen L. Zoological Journal of the Linnean Society 2024 2024-01-09 200 2 547 617 Young & Wilberg & Johnson & Herrera & Brandalise & Andrade & Brignon & Sachs & Abel & Foffa & Fernández & Vignaud & Cowgill & Brusatte, 2024 [903,1073,796,823] Euthalattosuchia Animalia Crocodylia 50 597 genus  RegNum registration number 1016.   Etymology ‘True sea crocodiles’. Eu- is the Neo-Latinized form of the Greek ( εὖ, eû), meaning good or true. Thalatto- is from the classical Ancient Greek (θᾰ́λᾰ́ττᾰ́, thálatta) for sea. Suchusis 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 - suchusis today used to refer to crocodiles, crocodylian relatives, or crocodylian analogues. The Neo-Latin suffix - iadenotes an abstract noun of feminine grammatical gender.   Geological range Middle Jurassic (latest Aalenian or early Bajocian) to Early Cretaceous (earliest Aptian) ( Chiarenza et al. 2015, Wilberg 2015a, Sachs et al. 2020).  PhyloCode phylogenetic definition The smallest clade within  Metriorhynchoideacontaining  Zoneait nargorumWilberg 2015aand  Thalattosuchus superciliosus(Blainville in Eudes-Deslongchamps 1852).  Reference phylogeny  Fig. 3.   PhyloCode diagnostic apomorphies Metriorhynchoid crocodylomorphs with the following unique combination of characters (11): absence of external ornamentation on the lacrimal (20.1); antorbital cavity is open posteriorly and contiguous with the orbital cavity (51.1); middle-posterior regions of the antorbital cavities are greatly expanded compared to the nasopharyngeal ducts (52.1); nasopharyngeal ducts are conspicuously deepened dorsoventrally (57.1); lacrimal vertically oriented and only exposed in lateral view (164.1); fossa present anterior to the orbits, on the lacrimals and prefrontals, with most of the bony surface anterior to the orbit concave (179.2); prefrontal dorsal surface is greatly expanded laterally, overhanging part of the orbit (205.2); ectopterygoid does not contact the maxilla (393.0); extreme enlargement of the cerebral carotid canal foramina, such that they are more than twice as large as any other foramina on the occipital surface (428.2); ulna less than 50% of humerus length (752.4); distal diaphysis of the ulna is flattened (763.1).   Composition   Zoneaitand  Metriorhynchidae.  Comments Authorship: This is a new nomen.  Prior phylogenetic definition:This clade has never been phylogenetically defined.  Discussion:We chose not to use Acutirostres Jaekel, 1910as the nomen for this clade, as Acutirostres has been used prior to 1910 to refer to birds. Unfortunately, the taxa united under Acutirostres differs between authors (see: De-Carlini 1888: 47; Morgana 1903: 28). Moreover, Jaekel (1910)used Acutirostres to unite his Metriorhynchidaeand Geosauridae, making it in a synonym of Metriorhynchidaeherein.As such, we do not recommend Acutirostres being used in thalattosuchian nomenclature. The establishment of Euthalattosuchiais our attempt to honour the intended composition of  Thalattosuchia sensu Fraas (1901, 1902). Fraas was clear that his three ‘familien’,  Metriorhynchus,  Geosaurus, and  Dacosaurus[sic] composed his  Thalattosuchia, and that the group was fully aquatic. As the nomen  Metriorhynchidaeis used for that clade, we created Euthalattosuchiafor a clade of metriorhynchoids that had both cranial and postcranial adaptations for an aquatic lifestyle (see: Wilberg 2015a).