Published on September 15th, 2025 | by David Marshall

The iguanodontians were an incredibly successful group within the Cretaceous. They could reach incredible sizes, with the largest species even matching the proportions of some sauropods, and they also had an incredible palaeogeographic range, meaning that their remains are found all over the world today. In the late Jurassic, they were a lot less diverse and much smaller, so the late Jurassic and early Cretaceous are key times for understanding the evolution of this group.

Cariocecus bocagei is a newly described iguanodontian from the Early Cretaceous of Praia do Areia do Mastro, Portugal. Whilst it is only know from a partial skull, there are numerous useful characteristics that help identify it as a new species and fill in our understanding of iguanodontians in this important time in their evolution.

Joining us in this episode is Dr Filippo Bertozzo of the Royal Belgian Institute of Natural Sciences.

[Audio coming soon. Video interview available here: https://youtu.be/2fviWUan97s]

Cariocecus bocagei was discovered in the Lower Cretaceous Papo Seco Formation of Praia do Areia do Mastro, Portugal.

The block of rock was collected for the teeth that were externally visible, but after painstaking preparation, numerous different bones from of the right side of the skull, parts of the skull roof, and a nearly complete braincase were recovered.

The bones of the skull were studied using a CT scanner and revealed exciting new details about its cranial nerves and allowing for the most detailed reconstruction of the soft tissues of a dinosaur’s inner ear ever made.

Cariocecus bocagei was confirmed as a new species by the fusion of the maxillo-jugal complex and the tri-lobed shape of the supraoccipital. The ossification of the maxilla and jugal is interesting considering that other bones of the skull are unosssified. This means that the individual was likely a sub-adult, having not reach full skeletal maturity, but for whom the fusion of these bones was an important trait, possibly to aid chewing and processing of harder materials.
Image: 3D reconstruction of Cariocecus bocagei by Fabio Manucci.

Cariocecus was also in possession of a uniquely-positioned supraorbital (the spike-shaped bone positioned close to the eye). This structure is present in modern crocodiles and birds and is associated with support of the ‘supraorbital membrane’, essentially a soft-tissue ‘roof’ to the top of the orbit. Like in birds such as eagles, this supraorbital bone would have given Cariocecus a prominent ‘eyebrows’ which could have benefited/protected the eye in many ways.
Image: Life reconstruction of Cariocecus bocagei by Fabio Manucci.

Strict consensus tree showing Cariocecus at the base of Hadrosauroidea. Cariocecus is closest related to the British species Brighstoneus simmonsi and Comptonatus chasei, showing the close ties between the European hadrosauroids in the Early Cretaceous and perhaps a European/African origin for the group.

Reconstruction of Cariocecus bocagei by Victor Feijó de Carvalho.

Dr Filippo Bertozzo with part of SHN.832, the holotype of Cariocecus bocagei.

Tags: CT, Dinosaur, Iguanodon, Iguanodontian, Ornithopod, Portugal, skull