winalski@psw.enet.dec.com (Paul S. Winalski) (04/24/91)
In article <1991Apr23.082506.29920@kuhub.cc.ukans.edu>, mcginnis@kuhub.cc.ukans.edu writes: |>Thanks for the answers about monotremes. The summary answer is |>that these animals (3 species: duck billed platypus, and the long |>and short snouted echidna, spiney ant-eater) have a common cavity |>called the urogenital sinus, or cloaca, into which all major internal |>organs that dump stuff outside of the body dump their stuff (urine, |>feces, and sperm). Hence the name monotreme (Latin for "one hole"). |>I haven't heard whether they have a separate uterus... I assume |>that they must. They don't have any uterus at all. They lay eggs. |>Apparently some other mammals other than monotremes (monotreme means |>"one hole" in Latin, I am told) have a urogenital sinus: armadillo |>and sloth for example. |> |>It sounds to me like monotreme is a misnomer and we use it to refer to |>oviparous mammals and that all of these animals (plus some others) |>happen to have a urogenital sinus. Etymology has nothing to do with the specificity of a scientific term. Monotremata and monotreme may derive from the Latin for one sinus, but that does not mean that all organisms with that characteristic are monotremes. Likewise, hedgehogs and porcupines are not echinoderms even though they have spiny skin. --PSW