noun
- Plural of prototherian; members of the most primitive order of living mammals, including monotremes such as the platypus and echidna, characterized by laying eggs and having a single opening for reproductive and excretory functions.
Usage: zoology; technical
Examples
- Prototherians are the only mammals that lay eggs rather than bearing live young.
- The platypus and echidna are the most well-known examples of prototherians.
- Scientists study prototherians to understand the early evolution of mammals.
- Unlike other mammals, prototherians lack a placenta and mammary glands in the traditional sense.
- Prototherians represent a unique branch of mammalian evolution found primarily in Australia and nearby regions.