Perissodactyla is one of the two groups of ungulates – mammals walking on the tips of their toes. Including Perissodactyls, most ungulates possess hooves on their feet as opposed to claws. Perissodactyls are the ungulates that are odd-toed, as the number of toes is reduced. For e.g., from five down to one in horses and three, seen in rhinoceroses.
The even-toed ungulates, Artiodactyla, have four toes as seen in hippopotamuses, camels, pigs or two as seen in cattle, sheep, deer, etc. The ungulates are entirely terrestrial and collect food with the help of their mouths. This is because the structure of their feet prevents climbing or grasping; it has mainly evolved for the purpose of locomotion.
The dynamics between Perissodactyla and Artiodactyla are somewhat complicated. In some of the phylogenies, they have been set up together in a clade of Euungulata. In some others, these two clusters show a more distant relationship (Perissodactyla being associated with Carnivora in a lineage that is disconnected from the Artiodactyla).
Key Differences between Perissodactyla and Artiodactyla
The table below depicts the differences between Perissodactyla and Artiodactyla.
|
Perissodactyla |
Artiodactyla |
|
Toes |
|
|
Odd-toed ungulates |
Even-toed ungulates |
|
Alisphenoid Canal |
|
|
Present |
Absent |
|
Horns |
|
|
Absent mostly. |
Present usually and could be solid or hollow, situated on the frontal bone. |
|
Digits |
|
|
The third digit only is stout, and the axis of the limb passes down the third digit (Mesaxonic condition.) |
The third and fourth digits are larger bearing hoofs. The axis of the limb is seen passing between the third and fourth digits (Paraxonic condition). |
|
Dorsolumbar Vertebrae |
|
|
More than 22 |
19 |
|
Cellulose Digestion Efficiency |
|
|
45% |
60% |
|
Axis of Support |
|
|
Passes through the third digit. |
Passes through the third and fourth digits. The digits 1, 2 and 5 are either lost or reduced. |
|
Grazers/browsing Animals |
|
|
Primarily grazers. |
Grazers and browsing animals. |
|
Femur |
|
|
Third trochanter is present. |
Third trochanter is absent. |
|
Nasals |
|
|
Present |
Not expanded posteriorly. |
|
Odontoid Process |
|
|
Peg-like |
Spout-like |
|
Examples |
|
|
Donkey, Horse, Rhinoceroses |
Camels, Sheep, Deer, Cattle |
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