monotreme
noun
mono·treme ˈmä-nə-ˌtrēm 
: any of an order (Monotremata) of egg-laying mammals comprising the platypuses and echidnas
Example Sentences
Recent Examples on the Web Content includes video, images, and questions designed to teach students about mammals, birds, primates, bears, reptiles, monotremes, marsupials and others. 
Tracy Maness, Houston Chronicle, 6 Apr. 2020 Males of the Australian monotremes — egg-laying mammals — produce venom in their thighs during mating season and deliver the poison to competitors via hollow spurs just above their webbed feet.8. Gemma Tarlach, Discover Magazine, 25 Sep. 2018 The platypus is part of a small group of animals called monotremes, which lay eggs and produce milk to feed their young. Maria Clark, NOLA.com, 19 Mar. 2018 Around 80 million years later, the monotremes—or egg-laying mammals—split off from the mammalian lineage, says Rebecca Young, a biologist at the University of Texas at Austin. National Geographic, 30 July 2016 There are three kinds of mammals: egg-laying monotremes such as the platypus, marsupials like kangaroos and opossums, and the majority—placental, or eutherian, mammals—including humans and about 4400 other mammal species. Elizabeth Pennisi, Science | AAAS, 19 June 2017 Though monotremes' fossil record is limited, some skulls have been found, such as the extinct Obdurodon dicksoni. National Geographic, 30 July 2016 See More
Tracy Maness, Houston Chronicle, 6 Apr. 2020 Males of the Australian monotremes — egg-laying mammals — produce venom in their thighs during mating season and deliver the poison to competitors via hollow spurs just above their webbed feet.8. Gemma Tarlach, Discover Magazine, 25 Sep. 2018 The platypus is part of a small group of animals called monotremes, which lay eggs and produce milk to feed their young. Maria Clark, NOLA.com, 19 Mar. 2018 Around 80 million years later, the monotremes—or egg-laying mammals—split off from the mammalian lineage, says Rebecca Young, a biologist at the University of Texas at Austin. National Geographic, 30 July 2016 There are three kinds of mammals: egg-laying monotremes such as the platypus, marsupials like kangaroos and opossums, and the majority—placental, or eutherian, mammals—including humans and about 4400 other mammal species. Elizabeth Pennisi, Science | AAAS, 19 June 2017 Though monotremes' fossil record is limited, some skulls have been found, such as the extinct Obdurodon dicksoni. National Geographic, 30 July 2016 See More Word History
Etymology
New Latin Monotremata, from Greek mon- + trēmat-, trēma hole — more at trematode
First Known Use
1835, in the meaning defined above
Kids Definition
monotreme
noun
mono·treme ˈmä-nə-ˌtrēm
: any of a small group of egg-laying mammals that includes the platypus
Medical Definition
monotreme
noun
mono·treme ˈmän-ə-ˌtrēm
: any mammal (as a platypus) of the order Monotremata