Osteoderm in the context of "Armour (zoology)"

Keratin (/ˈkɛrətɪn/) is one of a family of structural fibrous proteins also known as scleroproteins. It is the key structural material making up scales, hair, nails, feathers, horns, claws, hooves, and the outer layer of skin in tetrapod vertebrates. Keratin also protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, birds, amphibians, and mammals. Excessive keratinization participate in fortification of certain tissues such as in horns of cattle and rhinos, and armadillos' osteoderm. The only other biological matter known to approximate the toughness of keratinized tissue is chitin.Keratin comes in two types: the primitive, softer forms found in all vertebrates and the harder, derived forms found only among sauropsids (reptiles and birds).

Aetosaurs (/eɪˌɛtoʊˈsɔːr/) are heavily armored reptiles belonging to the extinct order Aetosauria (/eɪˌɛtoʊˈsɔːriə/; from Greek, ἀετός (aetos, "eagle") and σαυρος (sauros, "lizard")). They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs more closely related to crocodilians than to birds and non-avian dinosaurs. All known aetosaurs are restricted to the Late Triassic, and in some strata from this time they are among the most abundant fossil vertebrates. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms (bony scutes). Aetosaur fossil remains are known from Europe, North and South America, parts of Africa, and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.

Nearly all aetosaurs (except for the genus Aetosauroides) belong to the family Stagonolepididae. Over 20 genera of aetosaurs have been described, and recently there has been controversy regarding the description of some of these genera. Two distinct subdivisions of aetosaurs are currently recognized, Desmatosuchia and Aetosaurinae, based primarily on broad differences in skull morphology. Osteoderms structure is generally one of the most useful traits for inferring aetosaur relations more precisely. Among other archosaurs, aetosaurs are most closely related to Revueltosaurus, a small reptile originally known from teeth mistakenly referred to herbivorous dinosaurs.

Thalattosuchia is a clade of mostly marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of Crocodilia and records from Thailand and China suggest that some members lived in freshwater. The clade contains two major subgroupings, the Teleosauroidea and Metriorhynchoidea. Teleosauroids are not greatly specialised for oceanic life, with back osteoderms similar to other crocodyliformes. Within Metriorhynchoidea, the Metriorhynchidae displayed extreme adaptions for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin, and probably gave live birth, seemingly uniquely among archosaurs.

Glyptotherium (from Ancient Greek for 'grooved or carved beast') is a genus of glyptodont (an extinct group of large, herbivorous armadillos) in the family Chlamyphoridae that lived from the Early Pliocene, about 3.9 million years ago, to the Late Pleistocene, around 15,000 years ago. It was widely distributed, living in the United States, Mexico, Guatemala, Costa Rica, Honduras, El Salvador, Panama, Venezuela, Colombia, and Brazil. Fossils that had been found in the Pliocene Blancan Beds in Llano Estacado, Texas were named Glyptotherium texanum by American paleontologist Henry Fairfield Osborn in 1903. Another species, G. cylindricum, was named in 1912 by fossil hunter Barnum Brown on the basis of a partial skeleton that had been unearthed from the Pleistocene deposits in Jalisco, Mexico. The two species differ in several aspects, including age: G. texanum is from the older Early Pliocene to Early Pleistocene strata, whereas G. cylindricum is exclusive to the Late Pleistocene.

Glyptotherium was a large, four-legged (quadrupedal), herbivorous armadillo with an armored top shell (carapace) that was made of hundreds of interconnected osteoderms (structures in dermis composed of bone). Other pieces of armor covered the tail and cranium roof, while small pebbly pieces of armor were in the skin. Glyptotherium grew up to 2 meters (6.56 feet) in length and 400 kilograms (880 pounds), making it one of the largest glyptodonts known. Glyptotherium is morphologically most similar to Glyptodon: though they differ in several ways. Glyptotherium is smaller on average, with a shorter carapace, a longer tail, and had a different distribution.

Stegosaurus (/ˌstɛɡəˈsɔːrəs/; lit. 'roof-lizard') is a genus of herbivorous four-legged armored dinosaurs from the Late Jurassic, characterized by the distinctive kite-shaped upright plates along their backs and spikes on their tails. Fossils of the genus have been found in the western United States and in Portugal, where they are found in Kimmeridgian- to Tithonian-aged strata, dating to between 155 and 145 million years ago. Of the species that have been classified in the upper Morrison Formation of the western US, only three are universally recognized: S. stenops, S. ungulatus and S. sulcatus. The remains of over 80 individual animals of this genus have been found. Stegosaurus would have lived alongside dinosaurs such as Apatosaurus, Diplodocus, Camarasaurus and Allosaurus, the latter of which may have preyed on it.

They were large, heavily built, herbivorous quadrupeds with rounded backs, short fore limbs, long hind limbs, and tails held high in the air. Due to their distinctive combination of broad, upright plates and tail tipped with spikes, Stegosaurus is one of the most recognizable kinds of dinosaurs. The function of this array of plates and spikes has been the subject of much speculation among scientists. Today, it is generally agreed that their spiked tails were most likely used for defense against predators, while their plates may have been used primarily for display, and secondarily for thermoregulatory functions. Stegosaurus had a relatively low brain-to-body mass ratio. It had a short neck and a small head, meaning it most likely ate low-lying bushes and shrubs. One species, Stegosaurus ungulatus, is one of the largest known of all the stegosaurians, with the largest known specimens measuring about 7.5 metres (25 ft) long and weighing over 5 metric tons (5.5 short tons).

Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous.

Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Primitive forms had simple, low, keeled scutes or osteoderms, whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans were herbivorous and had relatively small brains for their body size.