“The rock contains what appears to be a horizontal section of a dinosaur’s skull. The image looks like a CT scan, and clearly shows the cranium, the nasal cavities, and numerous teeth,” Andrea Tintori, the University of Milan paleontologist who spotted the fossil near the altar, told Discovery News.
Measuring about 30 cm (11.8 inches), the skull was cut in sections as slabs of the marble-like rock were used to build the Cathedral between 1532 and 1660.
Indeed, Tintori found a second section of the same skull in another slab nearby.
The calcareous rock in which the dinosaur remains are embedded comes from the rich fossil-bearing site of Mount San Giorgio, which is on the Unesco World Heritage List.