Definition of "monotreme" [mon•o•treme]

• A member of the Monotremata, an order of primitive egg-laying mammals restricted to Australia and New Guinea and consisting of only the platypus and the echidna. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The word monotreme combines the Greek words, μονο and τρεμα, for one and hole."
• "No, the label monotreme refers to the order of mammals which lay eggs."
• "A 15 million-year-old complete skull and nearly complete dentition of the monotreme Obdurodon dicksoni has already provided a great deal of new information about this highly distinctive group of mammals."