Difference between Prototheria and Theria are given below:
Prototheria
1. External ear on pinnae is absent.
2. Teeth are absent in the adult condition.
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3. Cloaca is present.
4. Mammary gland is present but nibble is absent.
5. Testes are abdominal.
6. Corpus collasm absent.
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7. Egg laying animals.
Theria
1. External ear pinnae are present.
2. Teeth are well developed.
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3. Cloaca is absent.
4. Mammary gland is present with nipple.
5. Tests are descending in to scrotal sac.
6. Urethra is common for vasa differentia and urinary bladders.
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7. Viviparous animals.