Antlers Vs. Horns, Part 2: Horns

A horn, unlike an antler, is attached to an animal.  It consists of a bony core, a projection of the bone of an animal, and is covered by a layer of keratin (your fingernails are composed of keratin).  Also unlike an antler, that falls off easily and annually, a horn, if it is broken off, will never grow back the same way.  That is why poachers have to kill rhinos (who have horns) to actually take their horns, as opposed to just letting them fall off.

Many different types of animals have horns.  Let's take a look at a few of these creatures.

The members of the family "Giraffidae," which includes the giraffe and the okapi, both have horn-like things on their heads, called "ossicones."

The members of the family "Rhinocerotidae," or the rhinos, have horns that are composed solely of keratin, and do not have the bone core typical of many horns.  The horns of the rhinos also grow continuously.

Some of the members of the family "Chamaeleonidae," or the chameleons, often have horns projecting out of their skulls, which are covered in a layer of keratin.

And, of course, the members of the family "Ceratopsidae," a group of marginocephalian dinosaurs, have horns projecting out of their skulls. 
Below is a short list of some of the more famous Ceratopsian dinosaurs.

Famous examples of Ceratopsian Dinosaurs (or "Ceratopsians That I Have Heard Of):

1. Triceratops - (Colorado, Montana, and Wyoming, U.S.; Alberta and Saskatchewan, Canada)
2. Arrhincoceratops - (Alberta, Canada)
3. Torosaurus - (Montana, North Dakota, South Dakota, Utah, and Wyoming, U.S.; Saskatchewan, Canada)
   
4. Monoclonius - (Montana, U.S.; Alberta, Canada)
5. Chasmosaurus - (Alberta, Canada)
   
6. Centrosaurus - (Alberta, Canada)
7. Styracosaurus - (Montana, U.S.; Alberta, Canada)
   
8. Achelousaurus - (Montana, U.S.)
9. Pentaceratops - (New Mexico, U.S.)
10. Vagaceratops - (Alberta, Canada)
    
11. Diabloceratops - (Utah, U.S.)
12. Albertaceratops - (Montana, U.S.; Alberta, Canada)
13. Einiosaurus - (Montana, U.S.)
14. Anchiceratops - (Alberta, Canada)
15. Mojoceratops - (Alberta and Saskatchewan, Canada)
16. Pachyrhinosaurus - (Alaska, U.S.; Alberta, Canada)
17. Kosmoceratops - (Utah, U.S.)
18. Medusaceratops (Montana, U.S.)
19. Utahceratops - (Utah, U.S.)

Keep in mind that the tusks seen in elephants, mammoths, walruses, and hippos, despite being superficially similar to horns, are actually greatly enlarged teeth!

Antlers Vs. Horns, Part 1: Antlers

Antlers and horns often look the same, but underneath, they are actually quite different!  Today we are going to look at not only what defines both antlers and horns, but also take a look at some of the animals that have each of them!  All aboard!

Let's start off with antlers.  As defined by the Google dictionary thing, an antler is "One of the branched horns on the head of an adult (usually male) deer, which are made of bone and are grown and cast off annually."  Something that I would like to add is that antlers are unique to the family Cervidae, which includes:

• Deer
• Elk
• Moose
• Caribou (Reindeer)

The only member of the family Cervidae that has horns on both the males and the females is the caribou, frequently referred to as the "reindeer."  However, it has been documented, on numerous occasions, for fertile females from other species of the cervids to occasionally grow antlers, but this is typically due to unusually high testosterone levels. 

The family Cervidae is one of the many families in the order Artiodactyla, frequently referred to as the "Even-Toed Ungulates" (so called because they either stand on two or four toes).  There are around 220 extant (still living, as opposed to extinct) species of artiodactyl, and included within this order are many familiar groups.  These groups, broken down by family, include:

• Camelidae (Camels and llamas)
• Suidae (Pigs)
• Tayassuidae (Peccaries, a close relative of pigs)
• Hippopotamidae (Hippopotamus)
• Tragulidae (Chevrotains, a type of small deer)
• Antilocapridae (Pronghorn)
• Giraffidae (Giraffe and okapi)
• Moschidae (Musk deer)
• Cervidae (Deer)
• Bovidae (Cattle, sheep, goats, antelope)

(Interestingly, the whales, dolphins, and porpoises should be included within the order Artiodactyla, but instead they have been placed within their own, separate order, Cetacea.  This area of the family tree is still messy, and a possible merging of the two orders, Artiodactyla and Cetacea, is being considered, which would create the order Cetartiodactyla.)

Also included within the order Artiodactyla is the extinct family Entelodontidae.  Later today, we will finally be getting around to what was supposed to be the monthly "What Is It?" challenge, but has turned into more of a quarterly or tri-monthly event!  Anyways, we will be announcing the winners of THE LAST CHALLENGE later this evening, after we look at horns!