Ichthyosaurs were a group of marine Mesozoic reptiles. Their presence in the Portuguese fossil record is scarce and ranges from the Sinemurian to the Toarcian. In this work we describe a new specimen—a nearly complete skull discovered in the Sinemurian of Praia de Água de Madeiros, São Pedro de Moel, Municipality of Marinha Grande (Portugal). This specimen represents the most complete and best preserved cranial remains from the Iberian Peninsula published to date. Phylogenetic analyses performed identified this specimen as a new genus and species, Gadusarus aqualigneus, the first to be identified in the Iberian Peninsula. The species is phylogenetically recovered as a baracromian ichthyosaur, part of the Neoichthyosauria and Parvipelvia clades.

Key words: Parvipelvia, Ichthyosauria, Gadusaurus aqualigneus , phylogeny, Sinemurian, São Pedro de Moel.

João Pratas e Sousa [jrp.sousa@campus.fct.unl.pt; ORCID: https://orcid.org/0000-0002-3305-6444] and María Ríos [maria.rios.iba@fct.unl.pt; ORCID: https://orcid.org/0000-0001-7242-1259], GeoBioTec, FCT-NOVA Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal; GEAL Museu da Lourinhã, Rua João Luís de Moura, Lourinhã, Portugal. Isabel Morais Roldão [iroldao@esfrl.edu.pt; ORCID: https://orcid.org/0009-0006-8630-2756], ESFRL Escola Secundária Francisco Rodrigues Lobo, Rua Afonso Lopes Vieira, Leiria,Portugal], GEAL Museu da Lourinhã, Rua João Luís de Moura, Lourinhã, Portugal. Eduardo Puértolas-Pascual [eduardo.puertolas@gmail.com; ORCID: https://orcid.org/0000-0003-0759-7105], Grupo Aragosaurus-IUCA, Departamento de Ciencias de la Tierra, Facultad de Ciencias, Universidad de Zaragoza, Calle Pedro Cerbuna 12, 50009 Zaragoza, Spain.