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| Cariocecus bocagei Bertozzo, Camilo, Araújo, Manucci, Kullberg & Cerio, 2025 Artwork by Victor F. Carvalho |
Abstract
In Portugal, iguanodontian dinosaurs are mostly known from the Late Jurassic of the Lourinhã Formation and are represented by dryosaurids and basal styracosternans. The Early Cretaceous record of iguanodontians in Portugal is scarce in comparison, with scattered and uninformative remains referred to Styracosterna indet. Here, we describe SHN.832, the first iguanodontian skull from Portugal, named Cariocecus bocagei gen. nov. sp. nov. The specimen was found in Praia do Areia do Mastro (Cabo Espichel, Sesimbra) in the Papo Seco Formation (lower Barremian), and comprises the right side of the skull, part of the skull vault and a nearly complete basicranium. Cariocecus bocagei is diagnosed based on autapomorphies such as the co-ossified maxillo-jugal complex and the trilobated shape of the supraoccipital. The phylogenetic analysis retrieves C. bocagei as a basal hadrosauroid in a clade with Comptonatus chasei and Brighstoneus simmondsi. Our biogeographical analysis emphasizes the effects of insular endemism during the Hauterivian–Aptian range in the European regions. We show that Iguanodontia originated in South America, and through a dispersal event towards North America during the Upper Jurassic, expanded their latitudinal range. Cariocecus and other early-diverging iguanodontians emerged during an eastward dispersal event in the Lower Cretaceous. We reconstructed the endocast, cranial nerves and inner ear of Cariocecus via segmentation of micro-computed tomography scanning, showing similarities with other Hadrosauriformes such as Iguanodon and Proa. We propose the most detailed inner ear soft-tissue reconstruction for a dinosaur so far, including the macula and sub-branches of the vestibulocochlear nerve, supported by the extant phylogenetic bracket. Based on the unossified suture of the cranial elements, we hypothesize that SHN.832 had not yet reached full skeletal maturity, and our restoration suggests a total skull length of about 45 cm. The supraorbital membrane was reconstructed based on the well-preserved supraorbital bone and comparison with modern taxa.
Keywords: Ornithopoda, Barremian, Papo Seco Formation, supraorbital, biogeography
Filippo Bertozzo, Bruno Camilo, Ricardo Araújo, Fabio Manucci, José Carlos Kullberg, Donald G. Cerio. 2025. Cariocecus bocagei, A New basal hadrosauroid from the Lower Cretaceous of Portugal. Journal of Systematic Palaeontology. 23(1); 2536347. DOI: doi.org/10.1080/14772019.2025.2536347 [15 Sep 2025]
