spendýr

Spendýr, the Icelandic term for mammals, refers to the class Mammalia, a diverse group of vertebrate animals within the phylum Chordata. Mammals are characterized by hair or fur, mammary glands in females that produce milk, and three middle ear bones. They are endothermic, typically with a four-chambered heart and a muscular diaphragm, and they generally give birth to live young, with exceptions among monotremes that lay eggs.

The class Mammalia is divided into three main groups: Prototheria (monotremes, egg-laying), Metatheria (marsupials), and Eutheria (placentals). Today, most mammals are placental and diverse, occupying a wide range of habitats from oceans and forests to deserts and tundras. They display a broad spectrum of diets, from herbivory to carnivory to omnivory.

Mammalian evolution began in the Mesozoic era, with early small, shrew-like forms related to cynodonts. The rise of flowering plants and mammals followed the dinosaur extinction, leading to rapid diversification, especially after the Paleocene.

Key features besides reproduction and warm-bloodedness include advanced brain development, especially in the neocortex, acute tactile and sensory abilities, and in many lineages, specialized teeth and jaw mechanisms. The fur provides insulation and helps in signaling and camouflage.

Humans are mammals, as are whales, bats, elephants, and many other species. Mammals have substantial ecological and economic roles, serving as predators, prey, pollinators, and sources of food, clothing, and companionship.