The palpebral bone is a small

dermal bone A dermal bone or investing bone or membrane bone is a bony structure derived from intramembranous ossification forming components of the vertebrate skeleton including much of the skull, jaws, gill covers, shoulder girdle and fin spines rays ( le ...

found in the region of the

eye socket In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is , o ...

in a variety of animals, including crocodilians and

ornithischian Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s. It is also known as the adlacrimal or supraorbital, although the latter term may not be confused with the supraorbital in osteichthyan fishes. In ornithischians, the palpebral can form a prong that projects from the front upper corner of the orbit. It is large in heterodontosaurids, basal

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous wo ...

s such as ''

Thescelosaurus ''Thescelosaurus'' ( ; ancient Greek - (''-'') meaning "godlike", "marvellous", or "wondrous" and (') "lizard") was a genus of small neornithischian dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was ...

'' (as ''Bugenasaura'') and ''

Dryosaurus ''Dryosaurus'' ( , meaning 'tree lizard', Greek ' () meaning 'tree, oak' and () meaning 'lizard'; the name reflects the forested habitat, not a vague oak-leaf shape of its cheek teeth as is sometimes assumed) is a genus of an ornithopod dinosaur ...

'', and basal

ceratopsians Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic ...

such as '' Archaeoceratops'';You Hailu and Dodson, Peter. (2004). Basal Ceratopsia. In: Weishampel, David B.; Dodson, Peter; and Osmolska, Halszka (eds.) ''The Dinosauria'' (2nd Edition). Berkeley: University of California Press. p. 478–493. in these animals, the prong is elongate and would have stuck out and over the eye like a bony

eyebrow An eyebrow is an area of short hairs above each eye that follows the shape of the lower margin of the brow ridges of some mammals. In humans, eyebrows serve two main functions: first, communication through facial expression, and second, preven ...

. As paleoartist

Gregory S. Paul Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dino ...

has noted, elongate palpebrals would have given their owners fierce-looking "

eagle Eagle is the common name for many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, j ...

eyes". In such cases, the expanded palpebral may have functioned to shade the eye.

References

Vertebrate anatomy Dinosaur anatomy Eye anatomy Skull {{Vertebrate anatomy-stub