Armour (or
armor, see
spelling differences) 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. Armoured structures are usually composed of hardened
mineral deposits,
chitin,
bone or
keratin.
Armour is evident on numerous animal species from both current and prehistoric times.
Dinosaurs such as
Ankylosaurus, as well as other
Thyreophora (armoured dinosaurs such as
Ankylosauria and
Stegosauria), grew thick plate-like armour on their bodies as well as offensive armor appendages such as the
thagomizer or a
club. The armour took many forms, including
osteoderms, spikes, horns and plates. Other dinosaurs such as
ceratopsian dinosaurs as well as some
sauropods such as
Saltasaurus and
Agustinia, grew armour to defend themselves, although armour in sauropods overall is uncommon.
In modern times, some
molluscs 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, whether 'cosmoid', 'ganoid' or 'placoid' and in some cases
spines, such as on fish such as the
stickleback. The
chalky plate, or
cuttlebone, of
cuttlefish also acts as armour. Most
reptiles have scaly skin which protects them from predators in addition to water retention; the
crocodile's exoskeleton and the shells of the
Chelonia -
tortoises,
turtles and
terrapins.
Numerous
mammals, although not as sturdy as reptilian armour, employ the use of spines and body armour, like the spines of the
Echidna and
spiny anteaters and of
porcupines and
hedgehogs. The bony shell of the
armadillos and the extinct
Glyptodon were very much like
Ankylosaurus' armour and modern armadillos curl up into a ball when threatened, making them unexposed due to their armour. Similarly, the
hairy plate-like scales of the
pangolin are employed in the same way and are constructed of the same material used in the offensive armour, the horn, of the
rhinoceros.
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,
antlers,
claws and
beaks,
clubs and
pincers, as developed in some
mammals,
birds,
reptiles (including dinosaurs, such as the
Dromaeosaurids claw and the
Ceratopsian horn) and
arthropods. Offensive armour is often used in conjunction with defensive armour and in some cases makes an animal almost unassailable.
See also
Category:Animal anatomyCategory:Dinosaur anatomyCategory:Articles lacking sources (Erik9bot)de:Knochenpanzerfr:Armure (zoologie)
