The epijugal, or armored cheek plate, of a Ceratopsian dinosaur is rarely ever found because there are only 2 per animal and they are often unrecognized while out in the field.  

Ceratopsia is a group of beaked, herbivorous dinosaurs that lived during the Cretaceous Period. The most famous member is the Triceratops, which went extinct 65 million years ago. 

Early members include the small bipedal Psittacosaurus that lived 125 - 105 million years ago. Later members like Triceratops became quadruped and developed large and elaborate facial frills and horns. 

Triceratops' head alone was one-third the length of its entire body and is the largest skull of any land animal. Although the exact function of the horns and frills are unknown, it is speculated they were used in combat with predators, as a way to regulate body temperature, or even as a courtship display for  mating.

The jugal bones below the eye dramatically point out sideways from the skull, making the skull appear triangular. The epijugal is the armored cheek plate that forms the unusually pronounced jugal horn.

Type: Ceratopsian indet. Epijugal
Age: Cretaceous: Maastrichtian (72-65 million years old)
Formation: Hell Creek Formation
Locality: Powder River County, Montana

Size: 2.13 x 1.25 x 1.31 inches
Weight: 1.40 oz.