A team of paleontologists from Portugal, Italy, the United States and Belgium has added another species of herbivorous dinosaur to the prehistoric catalog: Cariocecus bocagei.
Cariocecus bocagei. Image credit: Victor Feijó de Carvalho.
Cariocecus bocagei lived in what is now Portugal during the Barremian age of the Cretaceous period, around 125 million years ago.
The new species was a medium-sized iguanodontian, a group of herbivorous dinosaurs with strong bodies and complex teeth.
“Iguanodontians are an important part of the herbivorous dinosaur faunas in different ecosystems across the Cretaceous,” said Dr. Filippo Bertozzo, a paleontologist with the Royal Belgian Institute of Natural Sciences and Ci2Paleo (Centro de Paleobiologia e Paleoecologia, Sociedade de História Natural de TorresVedras), and his colleagues.
“At the end of the Jurassic, iguanodontians were limited in species diversity and body mass, with the largest one being Camptosaurus.”
“These dinosaurs were mostly confined to the central region of the northern part of the Jurassic landmasses corresponding to modern Wyoming, Tanzania and Portugal.”
“By the mid-Cretaceous, the clade had gained global distribution,” they added.
“The selective pressures and environmental factors that drove this diversification during the Jurassic-Cretaceous transition are still poorly understood, mainly because of the scarcity of iguanodontian material from various regions (e.g. South Africa) from the dawn of the Cretaceous.”
“Iguanodontians are amongst the first dinosaurs to have been discovered and studied, and much research has been aimed at investigating the role and function of their anatomical characteristics,” they said.
“However, various cranial features remain enigmatic, from the function of the supraorbital bone to their paleoneurology and sensory system.”
Digital assemblage of the Cariocecus bocagei skull. Image credit: Bertozzo et al., doi: 10.1080/14772019.2025.2536347.
A partial skull of Cariocecus bocagei was discovered in 2016 along the cliffs of western Portugal from the Papo Seco Formation.
About 37 cm long, the specimen is the first ever iguanodontian skull from this country.
“The specimen was discovered in the Papo Seco Formation along the south-western shore of the Setúbal Peninsula, approximately 200 m north of Praia do Areia do Mastro,” the paleontologists said.
“Detailed sequence analysis indicates that the Early Cretaceous units exposed along this margin were deposited during the fourth and final rifting episode associated with the formation of the Lusitanian Basin.”
The researchers examined the fossil and identified anatomical features never seen in any other iguanodontian species.
“The maxilla and the jugal bone are completely fused. We’ve never seen that in any other iguanodont,” Dr. Bertozzo said.
“It’s not a random abnormality. This is a truly unique trait — and therefore a new species.”
Micro-CT scans allowed the scientists to examine the cranial nerves and inner ear in exceptional detail.
“A skull is always a special find. It tells us far more than isolated bones,” Dr. Bertozzo said.
“In this case, we could even trace impressions of the brain and nerves, and reconstruct parts of the inner ear.”
“The structure of the balance organs and auditory nerves gives us clues about how this animal lived and oriented itself.”
“Another striking feature is an unusually low ‘eyebrow’ bone — lower than in any other known iguanodontian.”
“It likely supported a heavy brow ridge, possibly similar to those seen in modern eagles.”
“That kind of structure may have had functional or even visual significance.”
“The teeth of Cariocecus bocagei also offered surprising insights,” he added.
“Micro-CT scans revealed not only the visible teeth, but also replacement teeth embedded in the jaw — new teeth already forming to replace worn ones.”
“This kind of tooth replacement is typical for iguanodonts, but it has rarely been observed so clearly in early species.”
According to the team, Cariocecus bocagei may have had a more powerful bite than its relatives.
“The discovery of Cariocecus bocagei augments our understanding of the ecological structure of Early Cretaceous environments in the Lusitanian Basin, suggesting the presence of more than one iguanodontian species, mimicking the trend seen in other coeval habitats in the United Kingdom, Belgium, Spain and central Africa,” the authors said.
“The Barremian diversity of iguanodontian taxa was caused by insular endemism events, which originated after a dispersal of North American dryomorphs between the Late Jurassic and the Early Cretaceous.”
“In conclusion, the discovery of Cariocecus bocagei highlights the importance of the Hauterivian-Barremian-Aptian for the diversification and speciation of iguanodontians that led to the evolution of the more sophisticated hadrosaurids in the Turonian.”
The findings were published in the Journal of Systematic Palaeontology.
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Filippo Bertozzo et al. 2025. Cariocecus bocagei, a new basal hadrosauroid from the Lower Cretaceous of Portugal. Journal of Systematic Palaeontology 23 (1); doi: 10.1080/14772019.2025.2536347