monotreme


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to monotreme: placental mammal

monotreme

(mŏn`ətrēm'), name for members of the primitive mammalian order Monotremata, found in Australia, Tasmania, and New Guinea. The only members of this order are the platypusplatypus
, semiaquatic egg-laying mammal, Ornithorhynchus anatinus, of Tasmania and E Australia. Also called duckbill, or duckbilled platypus, it belongs to the order Monotremata (see monotreme), the most primitive group of living mammals.
..... Click the link for more information.
, or duckbilled platypus, and the several species of echidnaechidna
or spiny anteater,
animal of the order Monotremata, the egg-laying mammals. A short-legged, grayish brown animal, the echidna is covered with sharp quills and can protect itself by rolling into a tight bristly ball. It may reach 18 in. (46 cm) in length.
..... Click the link for more information.
, or spiny anteater. Although monotremes possess the distinguishing mammalian features of hair and mammary glands, they are unique among mammalsmammal,
an animal of the highest class of vertebrates, the Mammalia. The female has mammary glands, which secrete milk for the nourishment of the young after birth. In the majority of mammals the body is partially or wholly covered with hair; the heart has four chambers, and
..... Click the link for more information.
 in laying eggs rather than giving birth to live young. The eggs are like those of reptiles, with large yolks and leathery shells. Like birds and reptiles, monotremes have a single opening, the cloacacloaca
, in biology, enlarged posterior end of the digestive tract of some animals. The cloaca, from the Latin word for sewer, is a single chamber into which pass solid and liquid waste materials as well as the products of the reproductive organs, the gametes.
..... Click the link for more information.
, for the passage of liquid and solid wastes, the transfer of sperm, and, in the female, the laying of eggs. In addition, certain features of the skeletal structure are like those of reptiles, and the regulation of body temperature is less effective than in other mammals. Adult monotremes are toothless. The males possess spurs on their hind feet; these are connected to poison glands and are presumably used as weapons. Mammals are known to have evolved from reptiles; the monotremes probably branched off at an early stage of mammalian evolution and have retained many reptilian features. They are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
..... Click the link for more information.
, subphylum Vertebrata, class Mammalia, order Monotremata.
References in periodicals archive ?
What characteristic makes monotremes different from other mammals?
Australia has some of the strangest animals on Earth It is the only continent to have all three groups of mammals - placentals, marsupials, and monotremes.
For, according to this rule, if MAMMAL and MONOTREME have not yet been acquired, VERTEBRATE will not be triggered by an echidna-experience, even though that experience is in fact an experience of a vertebrate.
Ontogeny, genetic control, and phylogeny of female reproduction in monotreme and therian mammals.
The cards containing the terms to be defined (like monotreme, platypus, marsupial, etc.
The adaptation is clearly important: with the exception of the platypus and its fellow monotreme, the echidna, the reproductive successes of mammals sporting external testes (and, conceivably, happier sperm) eventually allowed them to crowd out every other mammal on Earth.
The true nature of this monotreme was the subject of long and intense debate and controversy within the scientific community.
Platypus are one of three monotreme (egg-laying mammal) species remaining in the world and exist only along the east coast of Australia and in Tasmania.
The claustrum is not missing from all monotreme brains.
While Geering (1983:table 5) recorded a single monotreme bone (platypus, Ornithorhynchus anatinus) from between spits A10NW to A14, neither this nor the echidna (Tachyglossus aculeatus) was identified during this study.
It also implies that today's monotreme descendants of T.