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Sclerotic rings are rings of
File:Tawny Frogmouth Skull.jpg, A skull of an extant
Sclerotic rings are rings of bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
found in the eyes of many animals in several groups of vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
s, except for mammals and crocodilia
Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...
ns. They can be made up of single bones or multiple segments and take their name from the sclera. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical, or which live underwater. Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
sclerotic rings are known for a variety of extinct animals, including ichthyosaurs, pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
s, and 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, but are often not preserved.
tawny frogmouth
The tawny frogmouth (''Podargus strigoides'') is a species of frogmouth native to the Australian mainland and Tasmania and found throughout. It is a big-headed, stocky bird, often mistaken for an owl, due to its nocturnal habits and similar colo ...
, showing large sclerotic rings.
File:Uroplatus_phantasticus_skull1.jpg, A skull of an extant satanic leaf-tailed gecko
''Uroplatus phantasticus'', the satanic leaf-tailed gecko, eyelash leaf-tailed gecko or the phantastic leaf-tailed gecko, is a species of gecko indigenous to the island of Madagascar. First described in 1888 by George Albert Boulenger, ''U. p ...
, showing large sclerotic rings.
File:Viatkogorgon skull.png, Skull and sclerotic ring of the gorgonopsian
Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skul ...
''Viatkogorgon
''Viatkogorgon'' is a genus of gorgonopsian (a type of therapsid, the group that includes modern mammals) that lived during the Permian period in what is now Russia. The first fossil was found at the Kotelnich locality near the Vyatka Ri ...
''.
File:Prosaurolophus maximus3.JPG, Sclerotic ring of the hadrosaur
Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which incl ...
''Prosaurolophus
''Prosaurolophus'' (; meaning "before ''Saurolophus''", in comparison to the later dinosaur with a similar head crest) is a genus of hadrosaurid (or duck-billed) dinosaur from the Late Cretaceous of North America. It is known from the remains of ...
''.
References
Vertebrate anatomy Dinosaur anatomy Eye Skull {{vertebrate-anatomy-stub