horns and horns: You've probably heard of these structures, but do you know what the difference is between them? Do you know which animals have horns and which ones have horns? These terms are very confused. For example, it is common sense that cows and oxen have horns, but no, these animals have horns! Let's understand the differences between these two structures?
These structures are visible and present in some large ungulates (hoofed mammals). They are collectively called cranial appendages. It is believed that they have the function of defense, social recognition, sexual presentation and dispute between males for females and territory.
In general, both the horns and the horns are derived from the frontal bone of the skull, but only the horns are usually branched. The horns are covered with keratin and the horns with a layer of highly vascularized skin called velvet.
The growth of the horns is accompanied by the deposition of keratin – a type of dead material, which extends beyond the bone projection, leaving only a part composed of this structure. They are found in males and females of current ruminant artiodactyl ungulates (ungulates that have even fingers): deer, bulls, antelopes, etc. They grow continuously and are not exchanged throughout the animal's life.
Bulls, like some other artiodactyl ungulates, have horns, not horns.
On the horns, as they grow, the velvet layer is covered and, unlike the horns, they are usually changed annually. The exchange takes place when the horn is “ripe”, with the interruption of circulation in the velvet, this way this structure dies and leaves the horns, leaving the bone exposed. At this point, the horn falls off and another springs into place, accompanied by a new layer of velvet.
Horns are found only on the males of most deer. However, they are also present in female reindeer and some caribou.
Horns are present in males of most deer species.
There are some variations of the horns and horns that deviate from the common pattern. The structures present on top of the giraffe's head, for example, despite being covered with skin, instead of keratin, are types of horns. In these animals, the horns are called ossicones and have a differentiated formation and constitution. Its growth does not occur from the frontal bone, but from a separate bone, which merges with the frontal bone during development, and after that, skin deposits occur.
Giraffes have horns (covered by skin) called ossicones, formed separately from the frontal bone.
Another variation of the horns can also be seen in rhinos. These animals have single horns, rather than paired horns, which do not develop above the eyes, as in other animals with horns, but in the midline of the nose region. Furthermore, they are made up only of keratin.
Rhinoceros have different horns; in them, these structures are not paired and do not have bone formation, in addition to being in the line of the nose
Distinguished horns are seen in antilocapras (artiodactyl ungulates native to North America). They have bone projections covered by skin, but this forms a stratum corneum around the bone, made up of keratin. In these animals, the bone nucleus is permanent, but the stratum corneum is renewed annually.
Antilocapras have horns made up of bone projections covered with skin, which form a keratin stratum corneum.
By Flávia Figueiredo
Graduated in Biology
Source: Brazil School - https://brasilescola.uol.com.br/biologia/cornos-chifres.htm
