Hystricomorpha

Wasserschwein Schaedelskelett-drawing

Hystricomorpha is an infraorder of rodents, which includes a variety of species from multiple families. The name "Hystricomorpha" has both a broad and a narrow definition, depending on the classification system used. In the broad sense, it encompasses all rodents that share certain morphological traits with the porcupines of the Old World, which are part of the family Hystricidae. In a more narrow sense, it refers specifically to a clade that includes the South American hystricognath rodents and a few other related groups.

Characteristics

Hystricomorph rodents are characterized by their unique dental and skull structures. They typically have a robust build, with strong, curved incisors that are well adapted for gnawing. Their molars are also distinctive, often with complex surface patterns suited for grinding a variety of plant materials. Many hystricomorphs have a long gestation period compared to other rodents, and they give birth to well-developed young.

Classification

The classification of Hystricomorpha has been subject to change as new genetic and morphological evidence becomes available. Traditionally, it was divided into two main groups: the Hystricognathi and the non-Hystricognathi. However, modern classifications based on molecular data have led to a reevaluation of these relationships.

Hystricognathi

The Hystricognathi includes several families of rodents, notably the Caviidae (guinea pigs and relatives), the Erethizontidae (New World porcupines), the Chinchillidae (chinchillas and viscachas), and the Hystricidae (Old World porcupines). This group is primarily characterized by a unique arrangement of their jaw muscles, which is different from that of other rodents.

Non-Hystricognathi

The non-Hystricognathi part of Hystricomorpha includes various species that do not share the hystricognathous jaw musculature. This group is more diverse in terms of ecology and morphology, including species such as the Dasyproctidae (agoutis and acouchis) and the Cuniculidae (pacas), among others.

Distribution and Habitat

Hystricomorph rodents are found in a wide range of habitats across the globe. They are particularly diverse in South America, where the majority of Hystricognathi species are found. However, members of this infraorder can also be found in North America, Europe, Africa, and Asia. They inhabit a variety of environments, from dense forests to arid deserts, adapting to a wide range of ecological niches.

Conservation

The conservation status of hystricomorph rodents varies widely among species. Some, like certain species of guinea pigs, have been domesticated and are common worldwide. Others, such as the porcupines, are widespread and not currently at risk. However, there are also many species with small distributions and specialized habitat requirements that are threatened by habitat destruction, hunting, and other human activities.

In Culture

Hystricomorph rodents have played various roles in human culture, from being considered pests to serving as important food sources or pets. The guinea pig, for example, has a long history of domestication and is used both as a pet and for meat in different parts of the world.