Ligamentisidonta

Ligamentisidonta is a subclass of mammals that includes the order Rodentia, which is characterized by their incisor teeth that grow continuously throughout their lives. This subclass is named for the presence of a ligament that connects the lower incisors to the mandible, allowing them to grow continuously. The incisors are constantly worn down by gnawing, and the ligament allows the teeth to be replaced from the roots without the need for a permanent tooth socket.

The subclass Ligamentisidonta is further divided into two infraclasses: Euarchontoglires and Glires. Euarchontoglires includes primates, tree shrews, and scaly-tailed squirrels, while Glires includes rodents and lagomorphs. This subclass is distinguished by the presence of a single pair of lower incisors that are continuously replaced, as well as a unique pattern of tooth growth and replacement.

The order Rodentia, which is the only order in the subclass Ligamentisidonta, is one of the most diverse and successful groups of mammals. Rodents are found on every continent except Antarctica and include a wide range of species, from tiny shrews to large capybaras. They are known for their ability to adapt to a variety of habitats and diets, and many species play important roles in ecosystems as both prey and predators.