"Big John" had a skull injury from fighting another Triceratops

The remains of a triceratops known as “Big John” have revealed some injuries to the skull that were likely sustained during combat with another triceratops, according to a new study published in the journal Scientific Reports.

“The Late Cretaceous dinosaur Triceratops was characterized by its large neck frill, which predominantly consisted of the hyper elongated parietal and squamosal bones. It also had two large supraorbital horns and a smaller nasal horn. This cranial ornamentation of Triceratops probably served several functions,” explained the study authors.

“The evolutionary predecessors of ceratopsids had a relatively developed frill, while the horns, if present, were reduced to simple protuberances. The primitive function of the frill, therefore, was that of visual display and/or species recognition.”

According to the researchers, the development of the solid frill and the long horns during the evolution of Triceratops suggests that their function was to protect the cervical region of the skull from blows inflicted by individuals of the same species. This means that the cranial ornaments in Triceratops were not only used for visual display, but also as a means of attack and defense.

Study lead author Ruggero D’Anastasio from the University of Chieti–Pescara and colleagues examined the fossilized remains of Big John, which was discovered in 2014 in the Upper Cretaceous Hell Creek Formation of Montana.

The team discovered a keyhole-shaped opening, or a fenestra, in the right squamosal bone. The surrounding bone surface was irregular and showed signs of inflammation that was possibly due to infection. 

“The lumen of this fenestra is partially filled with a ring of brownish material, which is particularly evident on the caudal and inferior edges,” said the researchers.  “The bone surface around the fenestra is irregular and characterized by plaquelike depositions of reactive bone that could resulted from periostitis; i.e., a non-specific inflammatory process, which can be triggered by different stimuli (e.g., trauma, infection).”

The analysis of samples taken from the larger margin of the fenestra revealed that the surrounding bone tissue is porous with lots of blood vessels compared to bone tissue that was collected further away from the fenestra, which indicates that the bone was newly developed.

The findings suggest that the fenestra was caused by a traumatic injury, and that the bone was healing at the time of Big John’s death. The experts believe that the injury was likely caused by the horn of another triceratops, and occurred at least six months before Big John’s death. 

“This study confirms the existence of intraspecific fighting in Triceratops. Furthermore, although the physiological and cellular mechanisms underlying the healing process in dinosaurs are still largely unknown, it would appear to be similar to those described in humans and mammals,” wrote the researchers.

“Further histological and microanalytical investigations on fossil remains with traumatic lesions might shed light on the bone physiopathology of these reptiles.”

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By Chrissy Sexton, Earth.com Staff Writer