Definition

1. Adjective:
   • Lacking a placenta: Describes mammals that do not develop a placenta during gestation. The young are born at a very early stage of development or are hatched from eggs.

Usage

• The term is used specifically in zoology and biology to classify certain types of mammals.
• It is typically used attributively (before a noun) to describe an animal or group of animals.

Examples

• Adjective:
  • Monotremes, like the platypus, are aplacental mammals that lay eggs.
  • The aplacental nature of marsupials means their young complete development in an external pouch.

Advanced Usage

• Scientific Classification: The term is used to create a taxonomic distinction from placental mammals (eutherians).
  • The study compared the reproductive systems of aplacental and placental species.

Variants and Related Words

• Placental (adj): Having or developing a placenta. This is the direct antonym.
  • Humans are placental mammals.
• Eutherian (n/adj): Synonym for placental mammal.
• Metatherian (n/adj): Synonym for marsupial mammal, which is aplacental.
• Prototherian (n/adj): Synonym for monotreme mammal, which is aplacental.

Synonyms

• Non-placental: A more general, descriptive synonym.

Antonyms

• Placental: Having a placenta.

Adjective

1. having no placenta
   • monotremes and marsupials are aplacental mammals