The new specimen represents the world’s oldest cerapodan ornithischian dinosaur, according to a team of paleontologists from Sidi Mohamed Ben Abdellah University, the University of Birmingham and the Natural History Museum, London.
The proximal femur of a cerapodan dinosaur from the El Mers III Formation of the Middle Atlas Mountains, Morocco. Image credit: Maidment et al., doi: 10.1098/rsos.241624.
“Cerapoda is a diverse clade of ornithischian dinosaurs with a global distribution,” said Dr. Susannah Maidment, a paleontologist with the Natural History Museum, London, and the University of Birmingham, and colleagues.
“A major component of Cretaceous terrestrial ecosystems, early diverging cerapodans were bipedal, with forelimbs modified for grasping, but by the Late Cretaceous, hadrosaurids and ceratopsids had evolved obligate quadrupedality and sophisticated chewing mechanisms, and they became the dominant herbivores of the northern hemisphere.”
“Cerapoda is composed of two major clades: Ornithopoda, which includes the non-hadrosaurid iguanodontians and the duck-billed hadrosaurids, and Marginocephalia, which includes the horned, frilled ceratopsians and the dome-headed pachycephalosaurs.”
“Cerapodans are well known from the Cretaceous period, but their Jurassic record is much poorer,” they noted.
“Several track sites from the Middle Jurassic suggest that large-bodied ornithopods — probably iguanodontians — had already evolved by this time, but their body fossils remain elusive.”
“To elucidate the early stages of the evolution of Cerapoda and to help resolve the numerous phylogenetic inconsistencies among different analyses, new specimens are needed, especially from historically undersampled localities.”
The new cerapodan specimen — a portion of a left femur — was surface-collected in 2020 in the El Mers III Formation at Boulahfa, near Boulemane, Middle Atlas Mountains, Morocco.
The fossil is Bathonian (Middle Jurassic) in age, and dates to between 165 and 160 million years ago.
“The variegated green and red mudstones of the formation are extremely fossiliferous and have so far yielded the remains of the world’s oldest, and first African, ankylosaur, Spicomellus afer, and one of the oldest stegosaurs, Adratiklit boulahfa,” the paleontologists said.
The new specimen is the world’s oldest cerapodan and only the second recorded from the Middle Jurassic globally.
“The specimen, although fragmentary, bears characteristics, including a femoral head offset on a distinct neck and a constriction between the head and greater trochanter, that unite it with Cerapoda to the exclusion of other neornithischians,” the researchers said.
“Further sampling of the El Mers III Formation of Morocco is crucial for understanding the Middle Jurassic radiation of ornithischian dinosaurs.”
The team’s paper was published on March 12, 2025 in the journal Royal Society Open Science.
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Susannah Maidment et al. 2025. The world’s oldest cerapodan ornithischian dinosaur from the Middle Jurassic of Morocco. R. Soc. Open Sci 12 (3): 241624; doi: 10.1098/rsos.241624
