A horn is a bony projection (that is to say formed by bone ) and pointed that arises from the frontal bone of the skull of various animals. It is surrounded by a sheath of keratin that forms a horny sheath – or a skin, in the case of giraffes and okapis .
Summary
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- 1 Features
- 2 Similar structures
- 3 Uses for the species
- 4 Other uses
- 5 sources
Characteristic
Horn cores begin as small bony growths under the skin , on the skull , in the subcutaneous connective tissue. They are not attached to the skull and are known as “osicones”. The osiconum has its own ossification center and is fused to the cranial bones secondarily.
The horns are presented in pairs and take various forms depending on the family:
- Antilocapridae: Horns ending in a point and with some branching.
- Giraffidae: Bony protuberances covered with hairy skin.
- Bovidae: Horns are spirally bent cones made of keratin.
similar structures
giraffe horns
The horns of the giraffe (family Giraffidae ) are short, unbranched, permanent, paired bony processes, which are covered by skin and hair. They differ from the horns of other artiodactyls in that they are not projections of the frontal bones, but rest on the sutures between the frontal and parietal bones. Giraffe horns begin as cartilaginous structures in the fetus and may not fuse to the skull until the animal reaches 4 years of age. Horns are present on both sexes of giraffes, and even newborns.
rhinoceros horns
The horns of rhinoceroses (family Rhinocerotidae) differ from true horns in that they lack a nucleus or sheath. They are made up of a large number of epidermal cells and bundles of dermal papillae, which are extensions of the dermis. The cells corresponding to each papilla form a horny fiber similar to a coarse hair. These fibers, which are matted by the mass of epidermal cells, are not true hairs. True hair grows from follicles that extend into the dermis, while rhinoceros horns grow from dermal papillae that extend up into the horn. The horn is situated above the nasal bones. In species that have two horns, the second is found on the frontal bones. Commonly, the horns ofrhino curl back.
pronghorn horns
The pronghorn (Antilocapra americana) , belonging to the North American family Antilocapridae, has characteristic upright horns. These horns differ from bovid horns in two important ways. First of all, they are branched. Each horn has a short, backward-facing branch near its base, and a short, forward-facing hook near the tip. Second, while the horns consist of a bony core and a keratinized sheath as in bovids, the sheaths are replaced annually. In bovids, the sheaths always form a permanent part of the horn.
Uses for the species
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The horns are frequently used by males in fights and displays during the breeding season. These fights often include clashes that establish body strength. In general (but with many exceptions), horns are present on both sexes of larger species, but absent on females of smaller species. This is probably because large species are more likely to fight, while smaller species tend to run or hide. In species in which both sexes have horns, there is usually some degree of sexual dimorphism. Male horns are thicker at the base and can withstand greater forces. In females the horns are straighter and thinner, which could make them better for stabbing (defensive weapons).
Other uses
In certain cultures , bovine horns are used as musical instruments, for example, the shofar. These have evolved into wind instruments in which, unlike trumpets, the tube becomes wider than it is long. That is, they are more conical than cylindrical and are still called horns despite being made of metal .