fenestra

In most meat-eating dinosaurs, a ridge of bone provides a roof over an opening in the skull in front of the eye sockets known as the antorbital fenestra.

Pterosaurs also had extra openings in their skulls, the largest of which was an opening in front of the eyes known as an antorbital fenestra.

In the past, scientists believed the two large features in the roof of the extinct predator's skull - called the dorsotemporal fenestra - were filled with muscles that assist with jaw movements.

But what has been revealed of the snout is highlighting unknown anatomical features of , including a large antorbital fenestra, or hollow space in the skull, which would have influenced the tone of the Apatosaur's calls.

One of these “intermediate” triceratops skulls is on public display in the University of California Museum of Paleontology and clearly shows the emerging fenestrae, or holes, in the bony shield of the skull.