A collaborative team of paleontologists from Portugal, Italy, the United States, and Belgium has enriched their paleontological records with the identification of a new herbivorous dinosaur species: Cariocecus bocagei.

Cariocecus bocagei inhabited what is now known as Portugal during the Valemia period of the Cretaceous, approximately 125 million years ago.

This newly identified species belonged to the medium-sized Iguanodon group, which includes robust herbivorous dinosaurs with intricate teeth structures.

“The Iguanodon faction plays a significant role in the herbivorous dinosaur fauna across various ecosystems of the Cretaceous period,” stated Dr. Filippo Bertozzo, a paleontologist at the Royal Institute of Natural Sciences and ci2paleo (Centro de Perebierosia de Nature Ecology, Paleontology of Rehabilitation Therapy).

“At the conclusion of the Jurassic, the Iguanodon factions exhibited limited diversity and body size, with the largest being Camptosaurus.

“These dinosaurs were primarily restricted to the central part of the northern landmass of the Jurassic, which now includes modern-day Wyoming, Tanzania, and Portugal.”

“By the mid-Cretaceous, these clades had achieved a worldwide distribution,” they further commented.

“The selective pressures and environmental factors that drove this diversification during the Jurassic to Cretaceous transition remain poorly understood, largely due to the scarcity of iguanodontian fossils in various regions, such as South Africa.

“The Iguanodon faction was among the first dinosaurs to be discovered and researched, with ongoing studies aimed at exploring the anatomical features and their functions,” they remarked.

“Nonetheless, various aspects of the skull, from the function of the supraorbital bone to paleoneurology and sensory systems, continue to be elusive.”

Digital reconstruction of the skull of Cariocecus bocagei. Image credit: Bertozzo et al., doi: 10.1080/14772019.2025.2536347.

The partial skull of Cariocecus bocagei was uncovered in 2016 along the cliffs of West Portugal from the Paposeco Formation.

This specimen, measuring approximately 37 cm long, is the first Iguanodontian skull recorded in the country.

“The specimen was excavated from the Seco Formation of Papo along the southern coast of the Setubal Peninsula, roughly 200 meters north of Praia de Areia do Mastro,” noted the paleontologist.

“A comprehensive sequence analysis indicates that the early Cretaceous layers found along this coastline were deposited during the fourth and final uplift episodes related to the formation of the Lusitania Basin.”

Upon examining the fossils, researchers identified anatomical characteristics not observed in other Iguanodon species.

“The upper jaw and Jugal bones are flawlessly fused. I have never encountered this in any other iguanodon,” Dr. Bertozzo expressed.

“This isn’t a random anomaly; it’s a genuinely unique feature, confirming it as a new species.”

MicroCT scans enabled scientists to explore the cranial nerves and inner ear with remarkable detail.

“A skull discovery is always significant. It reveals much more than isolated bones,” Dr. Bertozzo commented.

“In this instance, you can observe the impressions of the brain and nerves and even reconstruct parts of the inner ear.”

“The structure of the balance organs and auditory nerves offers insights into how this animal lived and oriented itself.”

“Another notable feature is the unusually low ‘brow’ bones, lower than those of other known Iguanodon factions.”

“This likely supported a heavy brow ridge akin to that of modern eagles.”

“Such structures may have implications for functionality or visibility.”

“The teeth of Cariocecus bocagei also provided remarkable insights,” he added.

“MicroCT scans uncovered not only visible teeth but also replacement teeth embedded within the jaw, designed to replace those that have worn down.”

“This tooth replacement mechanism is characteristic of iguanodons but is rarely observed in earlier species.”

The research team speculates that Cariocecus bocagei may have possessed a stronger bite relative to its kin.

“The discovery of Cariocecus bocagei enhances our understanding of the ecological dynamics within the Lusitania Basin’s early Cretaceous environment, indicating the presence of multiple Iguanodon species, reflecting trends seen in other symbiotic habitats in the UK, Belgium, Spain, and Central Africa,” the authors stated.

“The Valemian diversity in Iguanodon taxa resulted from island endemic events that emerged following the dispersal of dry morphs in North America during the Late Jurassic and Late Cretaceous periods.”

“In conclusion, the discovery of Cariocecus bocagei emphasizes the significance of the Balemian Psien of Hauteribia in the diversification and speciation of Iguanodonians, ultimately leading to the evolution of the more advanced Hadrosaurus in the Turonian period.”

Survey results 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 period of Portugal. Journal of Systematic Palaeontology 23(1); doi:10.1080/14772019.2025.2536347