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Lagomorpha

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Lagomorphs are a distinct order of mammals characterized by their unique dental and physical traits. The name Lagomorpha is derived from Ancient Greek terms meaning "hare shaped."

Pika
Pika

This group includes two living families: Leporidae, which contains rabbits and hares, and Ochotonidae, which contains pikas. Currently, there are 110 species of lagomorphs alive today. These animals inhabit almost every continent on Earth, with the exception of Antarctica, Madagascar, and the West Indies. While they are not native to Australia, humans have introduced them there, where they have successfully colonized many areas.

Bushhase
Bushhase

One of the most important ways to identify a lagomorph is by examining its teeth. While lagomorphs are closely related to rodents within the grandorder Glires, they possess significant differences. Most notably, lagomorphs have four upper incisors, which includes two smaller peg teeth located behind the larger ones. In contrast, rodents only have two upper incisors.

Alloptox japonicus
Alloptox japonicus

Like rodents, a lagomorph's incisors grow continuously throughout its life. This growth requires the animal to constantly chew on fibrous plant material to prevent the teeth from becoming too long. Additionally, while only the incisors of most rodents grow continuously, all of a lagomorph's teeth exhibit this continuous growth.

Palaeolagus skull
Palaeolagus skull

Lagomorphs have developed specialized biological processes to survive on a strictly herbivorous diet. Because they eat tough, fibrous plants, they must extract nutrients efficiently through a process called cecotrophy. First, the animal ferments fiber within a specialized part of the gastrointestinal tract called the cecum. This process produces soft pellets known as cecotropes. The lagomorph then reingests these cecotropes to absorb the nutrients in the small intestine. This method allows them to utilize energy from hard-to-digest vegetation that might otherwise be wasted. Like rodents, bats, and some insectivores, lagomorphs also possess a smooth-surfaced cerebrum.

There are two primary families within the order, each with different physical adaptations. The family Leporidae includes both rabbits and hares. Hares, belonging to the genus Lepus, are medium-sized mammals with long, powerful hind legs and large ears. They are often solitary and rely on speed and a "jinking" gait to escape predators.

Alaskan Hare Skeleton
Alaskan Hare Skeleton

Rabbits are generally smaller than hares and often live in colonial groups within burrows or nests called forms. The second family, Ochotonidae, consists of pikas. Pikas are small mammals, often with greyish-brown fur and almost no tail. Unlike leporids, pikas lack a highly arched skull and strong, long hind limbs. They are often found in mountainous regions, where they collect dried vegetation to create "haypiles" for winter food.

History shows that the lagomorph lineage has changed significantly over millions of years. In 1811, Johann Karl Wilhelm Illiger first distinguished them from rodents by calling them Duplicidentata. In 1855, the German naturalist Johann Friedrich von Brandt coined the name Lagomorpha. The group was not formally described as an order until American paleontologist James W. Gidley did so in 1912. Fossil evidence suggests that lagomorphs were much more diverse in the past. The fossil record contains approximately 75 genera and over 230 species, indicating that modern lineages may be in decline.

Fossil occurrences of leporids and ochotonids and global environmental change
Fossil occurrences of leporids and ochotonids and global environmental change

Evolutionary studies continue to refine our understanding of where these animals came from. In the late 20th century, many scientists believed the ancestor of lagomorphs was Eurymylus, a mammal from eastern Asia. However, 21st-century examination of fossils suggests they may instead descend from mimotonids. These were mammals in Asia during the Paleogene that shared similar body sizes and dental structures with early European rabbits like Megalagus turgidus. Some studies from 2008 even suggest an Indian origin, proposing that lagomorphs evolved in isolation when India was an island continent during the Paleocene.

Lagomorphs also exhibit unique reproductive and physical characteristics compared to other mammals. For instance, they are unusual among terrestrial mammals because the females are typically larger than the males. Their paws also differ from most mammals; instead of having paw pads, the bottoms of their feet are entirely covered in fur. This is a trait they share with red pandas. In terms of reproduction, many species produce large litters several times a year. While hares are precocial, meaning their young are born with eyes open and full fur, rabbits and pikas are altricial. This means their young, called kits, are born with their eyes and ears closed and without fur.

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🖼️ Images & Media (6)
File:Fossil occurrences of leporids and ochotonids and global environmental change.png
Fossil occurrences of leporids and...
File:Pika.jpg
Pika.jpg
File:Bushhase.jpg
Bushhase.jpg
File:Alaskan Hare Skeleton.jpg
Alaskan Hare Skeleton.jpg
File:Alloptox japonicus.jpg
Alloptox japonicus.jpg
File:Palaeolagus skull.jpg
Palaeolagus skull.jpg
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