Xenarthra

Xenarthra

Pink Fairy Armadillo (Chlamyphorus truncatus) (cropped)

OrthoMaM v10b 2019 116genera circular tree

Chaetophractus vellerosus3

SouthernThreeBandedArmadillo065b

Bradypus variegatus

Xenarthra is a superorder of placental mammals that includes the extant armadillos, tree sloths, and anteaters, as well as their extinct relatives. This group is primarily found in Latin America from northern Mexico to southern Argentina and Chile. Xenarthrans are characterized by their unique vertebral joints, which have extra articulations; this is the feature that the name "Xenarthra," meaning "strange joints," refers to. They are also distinguished by their low metabolic rates and body temperatures compared to other mammals.

Classification

Xenarthra is divided into two orders:

• Pilosa: This order includes the anteaters and sloths. The Pilosa is further divided into two families: Myrmecophagidae (anteaters) and Bradypodidae and Megalonychidae (sloths).
• Cingulata: This order consists of the armadillos and their extinct relatives.

Evolution

Xenarthrans are among the oldest surviving lineages of mammals, with fossils dating back to the Paleocene, approximately 59 million years ago. They were much more diverse in the past, with a range of sizes and habitats. The superorder has survived several mass extinctions, although its diversity has declined over time.

Habitat and Distribution

Xenarthrans are adapted to a variety of habitats, including tropical rainforests, grasslands, and deserts. They are exclusively found in the Americas, with the greatest diversity in South and Central America. Some species, like the nine-banded armadillo (Dasypus novemcinctus), have expanded their range into North America.

Conservation

Many xenarthran species are threatened by habitat destruction, hunting, and roadkill. Conservation efforts are in place to protect these unique animals, but challenges remain due to their specific habitat requirements and low reproductive rates.

Anatomy and Physiology

Xenarthrans have several unique anatomical and physiological traits. Their vertebral joints have additional articulations (xenarthrales), providing strength to the spine. Most have a low metabolic rate and a variable body temperature, which is unusual for placental mammals. Their diets and digestive systems are specialized for their respective feeding habits, from the insectivorous diet of anteaters to the herbivorous diet of sloths.

Cultural Significance

Xenarthrans have been part of human culture in their native ranges for thousands of years. They are featured in folklore and mythology and have been used for food, clothing, and tools. Today, they are also important for ecological tourism and conservation education.

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