Infraclass: Eutheria
Eutheria, or the placental mammals, is the largest infraclass within Mammalia. This page follows the American Society of Mammalogists’ Mammal Diversity Database (MDD v2.5), which recognizes 19 orders belong to Eutheria[1].
Members of Eutheria develop a complex placenta that supports the embryo throughout gestation, allowing for longer developmental periods and more fully formed offspring at birth. Placental mammals inhabit nearly every terrestrial and aquatic environment on Earth. They include primates, rodents, carnivores, bats, hoofed mammals, marine mammals, and specialized lineages such as hyraxes, pangolins, and elephant shrews.
Modern taxonomy divides Eutheria into several distinct orders based on evolutionary relationships, anatomy, and ecology.
Orders of Eutheria
| Order | Representative Animals | Species (approx.) |
|---|---|---|
| Afrosoricida (アフリカトガリネズミ目 / 非洲猬形目) | tenrecs, golden moles | ~55 |
| Macroscelidea (ジャンプネズミ目 / 鼩鼱目) | elephant shrews | ~20 |
| Tubulidentata (管歯目 / 管齿目) | aardvarks | 1 |
| Hyracoidea (岩狸目 / 蹄兔目) | hyraxes | ~4 |
| Proboscidea (長鼻目 / 长鼻目) | elephants | 3 |
| Sirenia (海牛目 / 海牛目) | manatees, dugongs | 5 |
| Cingulata (アルマジロ目 / 犰狳目) | armadillos | ~21 |
| Pilosa (ナマケモノ目 / 披毛目) | sloths, anteaters | ~10 |
| Primates (霊長目 / 灵长目) | humans, monkeys, apes | ~520 |
| Scandentia (トガリネズミ目 / 树鼩目) | tree shrews | ~20 |
| Dermoptera (皮翼目 / 翼手目) | colugos | 2 |
| Lagomorpha (ウサギ目 / 兔形目) | rabbits, hares, pikas | ~100 |
| Rodentia (齧歯目 / 啮齿目) | rats, squirrels, beavers | ~2600 |
| Eulipotyphla (真無盲腸目 / 食虫目) | moles, hedgehogs, shrews | ~500 |
| Chiroptera (翼手目 / 翼手目) | bats | ~1450 |
| Carnivora (食肉目 / 食肉目) | cats, dogs, bears, seals | ~330 |
| Perissodactyla (奇蹄目 / 奇蹄目) | horses, zebras, tapirs, rhinoceroses | ~17 |
| Artiodactyla (偶蹄目 / 偶蹄目) | cattle, sheep, pigs, deer, giraffes | ~400 |
| Cetacea (鯨目 / 鲸目) | whales, dolphins, porpoises | ~90 |