Definition

Noun: A placental mammal is a mammal that gives birth to relatively well-developed live young, following a period of gestation during which the developing embryo is nourished via a specialized organ called the placenta. This group includes the vast majority of living mammal species.

Examples

• Humans, dogs, and whales are all placental mammals.
• The evolution of the placenta was a key adaptation for placental mammals.
• Unlike marsupials, placental mammals have a longer gestation period.

Advanced Usage

• The term is often used in scientific and zoological contexts to distinguish this infraclass (Eutheria) from other mammalian groups like monotremes (egg-laying mammals) and marsupials (pouched mammals).
• It can be used attributively (like an adjective) in compound nouns, e.g., "placental mammal biology."

Variants and Related Words

• Eutherian (noun/adjective): The formal scientific synonym for a placental mammal or relating to placental mammals.
• Placenta (noun): The organ that connects the developing fetus to the uterine wall, allowing for nutrient uptake, waste elimination, and gas exchange.
• Non-placental mammal (noun): A collective term for monotremes and marsupials.

Synonyms

• Eutherian

Antonyms

• Marsupial (e.g., kangaroo, opossum)
• Monotreme (e.g., platypus, echidna)

Noun

1. mammals having a placenta; all mammals except monotremes and marsupials