Possible Clues:

• Odd creature with tail also includes a tailless variety
• Aussie amphibian, a tailless sort, also going round
• Supply at sea around a ton for animal
• Mammal with a bill
• Egg-layer additionally incorporating a species from the Isle of Man?
• Substitute salty pup for Australian mammal
• Flat-tailed animal also embodies a tailless sort
• Aquatic creature, a sort almost visible in addition
• Duck-billed animal
• Australian mammal with large bill and webbed feet