Edmontonia American Museum of Natural History

Armour or armor in animals is external or superficial protection against attack by predators, formed as part of the body (rather than the behavioural use of protective external objects), usually through the hardening of body tissues, outgrowths or secretions. It has therefore mostly developed in 'prey' species.

Composition

Armoured structures are usually composed of hardened

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

deposits, chitin, bone, or

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...

Species with armour

Armour is evident in numerous animal species from both current and prehistoric times.

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 ...

s such as ''

Ankylosaurus ''Ankylosaurus'' is a genus of armored dinosaur. Its fossils have been found in geological formations dating to the very end of the Cretaceous Period, about 68–66 million years ago, in western North America, making it among the last of the ...

'', as well as other

Thyreophora 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 ...

(armoured dinosaurs such as

Ankylosauria Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. ...

and

Stegosauria Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Euro ...

), grew thick

plate Plate may refer to: Cooking * Plate (dishware), a broad, mainly flat vessel commonly used to serve food * Plates, tableware, dishes or dishware used for setting a table, serving food and dining * Plate, the content of such a plate (for example: ...

-like armour on their bodies as well as offensive armour appendages such as the

thagomizer A thagomizer () is the distinctive arrangement of four spikes on the tails of stegosaurine dinosaurs. These spikes are believed to have been a defensive measure against predators.Carpenter, K., Sanders, F., McWhinney, L., and Wood, L. 2005. Ev ...

or a

club Club may refer to: Arts, entertainment, and media * ''Club'' (magazine) * Club, a ''Yie Ar Kung-Fu'' character * Clubs (suit), a suit of playing cards * Club music * "Club", by Kelsea Ballerini from the album ''kelsea'' Brands and enterprises ...

. The armour took many forms, including

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s, spikes, horns, and plates. Other dinosaurs such as

ceratopsian 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 Jurassi ...

dinosaurs as well as some

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

s such as ''

Saltasaurus ''Saltasaurus'' (which means "lizard from Salta") is a genus of saltasaurid dinosaur of the Late Cretaceous period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, ''Saltasaurus'' was characterized by ...

'', grew armour to defend themselves, although armour in sauropods overall is uncommon. Triceratopsskull

In modern times, some

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...

s employ the use of shells as armour, and armour is evident in the chitinous exoskeleton of arthropods. Fish use armour in the form of

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

, whether 'cosmoid', 'ganoid' or 'placoid' and in some cases spines, such as on fish such as the

stickleback The sticklebacks are a family of ray-finned fishes, the Gasterosteidae which have a Holarctic distribution in fresh, brackish and marine waters. They were thought to be related to the pipefish and seahorses but are now thought to be more closel ...

. The

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...

y plate, or

cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family Sepiidae, commonly known as cuttlefish, within the cephalopod A cephalopod is any member of the moll ...

, of

cuttlefish Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control o ...

also acts as armour. Most

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchoce ...

s have scaly skin which protects them from predators in addition to water retention; the crocodile's

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the l ...

and the shells of the Chelonia:

tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like other ...

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...

s and

terrapin Terrapins are one of several small species of turtle (order Testudines) living in fresh or brackish water. Terrapins do not form a taxonomic unit and may not be closely related. Many belong to the families Geoemydidae and Emydidae. The name "t ...

s. Numerous

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s employ the use of spines and body armour, although not as sturdy as reptilian armour, like the spines of the

echidna Echidnas (), sometimes known as spiny anteaters, are quill-covered monotremes (egg-laying mammals) belonging to the family Tachyglossidae . The four extant species of echidnas and the platypus are the only living mammals that lay eggs and the ...

s and of

porcupine Porcupines are large rodents with coats of sharp spines, or quills, that protect them against predation. The term covers two families of animals: the Old World porcupines of family Hystricidae, and the New World porcupines of family, Erethiz ...

s and

hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction ...

s. The bony shell of the

armadillo Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along wi ...

s and the extinct ''

Glyptodon ''Glyptodon'' (from Greek for 'grooved or carved tooth': γλυπτός 'sculptured' and ὀδοντ-, ὀδούς 'tooth') is a genus of glyptodont (an extinct group of large, herbivorous armadillos) that lived from the Pleistocene, around 2.5 m ...

'' were very much like ''Ankylosaurus armour and some modern armadillos curl up into a ball when threatened, making them unexposed due to their armour. Similarly, the

hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fin ...

y plate-like scales of the

pangolin Pangolins, sometimes known as scaly anteaters, are mammals of the order Pholidota (, from Ancient Greek ϕολιδωτός – "clad in scales"). The one extant family, the Manidae, has three genera: ''Manis'', ''Phataginus'', and ''Smutsia' ...

are employed in the same way and are constructed of the same material used in the offensive armour, the horn, of the

rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct species o ...

Usage

Armour, although all used for the sole intent to ward off attackers, can be split into defensive and offensive armour. Examples of offensive armour are horns,

hooves The hoof (plural: hooves) is the tip of a toe of an ungulate mammal, which is covered and strengthened with a thick and horny keratin covering. Artiodactyls are even-toed ungulates, species whose feet have an even number of digits, yet the rum ...

antler Antlers are extensions of an animal's skull found in members of the Cervidae (deer) family. Antlers are a single structure composed of bone, cartilage, fibrous tissue, skin, nerves, and blood vessels. They are generally found only on males ...

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthrop ...

s and beaks, clubs and pincers, as developed in some

s, birds,

s (including dinosaurs, such as the

dromaeosaurid Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meani ...

claw and the

horn) and

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, o ...

s. Offensive armour is often used in conjunction with defensive armour and in some cases makes an animal almost unassailable.

Composition

Species with armour

Usage

See also