mcginnis@kuhub.cc.ukans.edu (04/22/91)
Sorry if this isn't the best place for this posting... What is a monotreme? An article on the echidna in the Feb., 1991 Scientific American says that the echidna has "a cavity uncommon in mammals, into which all the internal organs empty...". Now, this is obviously wrong (because the heart doesn't empty into this cavity, nor do the lungs, etc.) so I presume that this single cavity gets the urine and sperm and feces. Is this correct? Please E-mail replies. Thanks.
larry@kitty.UUCP (Larry Lippman) (04/23/91)
In article <1991Apr22.111159.29888@kuhub.cc.ukans.edu> mcginnis@kuhub.cc.ukans.edu writes: >What is a monotreme? An article on the echidna in the Feb., 1991 >Scientific American says that the echidna has "a cavity uncommon in >mammals, into which all the internal organs empty...". Now, this >is obviously wrong (because the heart doesn't empty into this >cavity, nor do the lungs, etc.) so I presume that this single >cavity gets the urine and sperm and feces. Is this correct? The only definition I am aware of for "monotreme" is that of an egg-laying mammal, such as the duck-bill platypus and spiny anteater. The term "monotreme" arises from the order Monotremata, which encompasses such animals. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
pmcnally@telesci.uucp (Patty A McNally) (04/23/91)
In article <4896@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <1991Apr22.111159.29888@kuhub.cc.ukans.edu> mcginnis@kuhub.cc.ukans.edu writes: >>What is a monotreme? > > The only definition I am aware of for "monotreme" is that of an >egg-laying mammal, such as the duck-bill platypus and spiny anteater. >The term "monotreme" arises from the order Monotremata, which encompasses >such animals. "Monotreme" comes from "mon-", meaning "one", and "trema", meaning "hole". While most mammals have separate orifices for urine and feces, the monotreme has only one. Hence the name. Stephen J. Gould's recent book "Bully for Brontosaurus", a collection of his essays from the magazine Natural History, contains some interesting information on both the platypus and echidna. Also, the most recent issue of Natural History (May '91) contains a fascinating article on the platypus - its bill is capable of sensing weak electric fields. Since it closes its eyes, ears, and nostrils when it goes underwater looking for food, researchers feel that the bill is capable of detecting prey by sensing the electric field created by the movement of muscles in potential food. Patty McNally
sarima@tdatirv.UUCP (Stanley Friesen) (04/24/91)
In article <4896@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <1991Apr22.111159.29888@kuhub.cc.ukans.edu> mcginnis@kuhub.cc.ukans.edu writes: >>What is a monotreme? An article on the echidna in the Feb., 1991 >>Scientific American says that the echidna has "a cavity uncommon in >>mammals, into which all the internal organs empty...". Now, this >>is obviously wrong (because the heart doesn't empty into this >>cavity, nor do the lungs, etc.) so I presume that this single >>cavity gets the urine and sperm and feces. Is this correct? Quite correct, this cavity is called a 'cloaca' and is present in birds and reptiles, but not in most mammals. (I suspect that SA was trying to be 'polite' and avoid direct reference to such things as feces and urine). > The only definition I am aware of for "monotreme" is that of an >egg-laying mammal, such as the duck-bill platypus and spiny anteater. >The term "monotreme" arises from the order Monotremata, which encompasses >such animals. Monotreme is indeed the 'common' form of 'Monotremata'. The taxon in question is distinguished from other mammals by several characteristics. Posession of a cloaca is one, laying yolk-filled eggs is another, as is incubation of the eggs in a pouch, and lack of nipples (the milk just oozes out of a general region of the mother's breast, where it is lapped up by the infant). In fact they are mammals only in possesing milk (i.e. mammary glands), insulating hair, and (to some degree) endothermy. The only known monotremes are the Platypus and the various species of Spiny Anteater (or Echidna). There is essentially no fossil record of monotremes. -- --------------- uunet!tdatirv!sarima (Stanley Friesen)
rh@smds.UUCP (Richard Harter) (04/24/91)
In article <1991Apr22.111159.29888@kuhub.cc.ukans.edu> mcginnis@kuhub.cc.ukans.edu writes: >What is a monotreme? An article on the echidna in the Feb., 1991 >Scientific American says that the echidna has "a cavity uncommon in >mammals, into which all the internal organs empty...". Now, this >is obviously wrong (because the heart doesn't empty into this >cavity, nor do the lungs, etc.) so I presume that this single >cavity gets the urine and sperm and feces. Is this correct? Essentially, yes. Monotreme means one-holer. Reptiles and birds have a cloaca. The monotremata have a cloaca. All other mammals have are two holers. -- Richard Harter, Software Maintenance and Development Systems, Inc. Net address: jjmhome!smds!rh Phone: 508-369-7398 US Mail: SMDS Inc., PO Box 555, Concord MA 01742 This sentence no verb. This sentence short. This signature done.
coleman@maui.cs.ucla.edu (Michael Coleman) (04/25/91)
mcginnis@kuhub.cc.ukans.edu writes: >What is a monotreme? Isn't that a device used by musicians to keep themselves in time? Mike P.S. ;-) --
rh@smds.UUCP (Richard Harter) (04/25/91)
In article <209@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes: A good article about momotremes continues > In fact they are mammals only in possesing milk (i.e. mammary glands), > insulating hair, and (to some degree) endothermy. Bones. They have mammalian jaws. The inimitable Dr. Asimov argues in one of his columns that the fusion of the relevant bones in Platypus is not completed until after birth and the correct classification of Platypus is a Therapsid and not a mammal at all. -- Richard Harter, Software Maintenance and Development Systems, Inc. Net address: jjmhome!smds!rh Phone: 508-369-7398 US Mail: SMDS Inc., PO Box 555, Concord MA 01742 This sentence no verb. This sentence short. This signature done.
andrewt@cluster.cs.su.oz.au (Andrew Taylor) (04/25/91)
In article <209@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes: > There is essentially no fossil record of monotremes. The have been 3 fossil platypus finds in the last 10 years in Australia. The oldest is the 110 million year old opalised jaw of Steropodon galmani from Lightning Ridge. It was much larger than the present day platypus. The location was within the Antartic circle then and the annual average temperature would have been 5C. > In fact they are mammals only in possesing milk (i.e. mammary glands), > insulating hair, and (to some degree) endothermy. Views on the thermo-regulation of Echidnas are changing. Its recently been found that they hibernate. This allows them over-winter in the high country of the Australia Alps. They have been accused of primitive-thermoregulation and incomplete homeothermy. Instead their thermoregulation may be highly specialised. Like the platypus echidnas have highly sensitive electro-receptors but in the echnidna case's its not obvious what they are be used for. Everyone interested in trivia should know the male platypus has a venomous spur on its hind leg. Its purpose isn't certain. One suggestion is that it is used in territorial disputes. Andrew Taylor
sarima@tdatirv.UUCP (Stanley Friesen) (04/27/91)
In article <416@smds.UUCP> rh@smds.UUCP (Richard Harter) writes: >In article <209@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes: >Bones. They have mammalian jaws. The inimitable Dr. Asimov argues in one >of his columns that the fusion of the relevant bones in Platypus is not >completed until after birth and the correct classification of Platypus >is a Therapsid and not a mammal at all. Oops, I forgot that one!! (real silly of me given my paleontology background). I think Dr Asimov's reasoning is a little off. The way most paleontologists define mammals (in practice) is based on the *adult* jaw joint. That is any fossil that has a mammal type jaw joint is considered a mammal, and since most (all?) known fossils of these groups are of adults, that is the deciding stage of growth. Of course, if the switch to the secondary jaw articulation is delayed until after birth, this is just one more indication of how very *primitive* the monotremes are. -- --------------- uunet!tdatirv!sarima (Stanley Friesen)
sarima@tdatirv.UUCP (Stanley Friesen) (04/27/91)
In article <2340@cluster.cs.su.oz.au> andrewt@cluster.cs.su.oz.au (Andrew Taylor) writes: >In article <209@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes: >> There is essentially no fossil record of monotremes. > >The have been 3 fossil platypus finds in the last 10 years in >Australia. The oldest is the 110 million year old opalised jaw of >Steropodon galmani from Lightning Ridge. It was much larger than the >present day platypus. The location was within the Antartic circle then >and the annual average temperature would have been 5C. Jehosephat!! I am getting behind on my mammalian fossils! [I have been concentrating on dinosaurs]. I had heard (vaguely) about some sub-recent (Plio-Pliestecene) monotremes, But a mid-Cretaceous platypus I had *not* heard of! (BTW are you *sure* of that date, I would have thought that would be such a major find I would have heard of it). [Not that such an early momotreme is all that unexpected, given the apparent relationships]. >Views on the thermo-regulation of Echidnas are changing. Its recently been >found that they hibernate. This allows them over-winter in the high country >of the Australia Alps. They have been accused of primitive-thermoregulation >and incomplete homeothermy. Instead their thermoregulation may be >highly specialised. Quite true, controlled temperature reduction in winter could well be a specialization rather than a primitive trait. I suspect this requires more research. Thermoregulation is still poorly understood in many ways. Certainly there is no really good 'classification' of differing modes of thermoregulation. -- --------------- uunet!tdatirv!sarima (Stanley Friesen)
andrewt@cluster.cs.su.oz.au (Andrew Taylor) (04/27/91)
In article <217@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes: > I had heard (vaguely) about some sub-recent (Plio-Pliestecene) monotremes, > But a mid-Cretaceous platypus I had *not* heard of! > (BTW are you *sure* of that date, I would have thought that would be such > a major find I would have heard of it). The 110 million year date is correct (see Nature 318:363-366). Also in 1985 a 15 million year old platypus skull (Obdurodon dicksoni) was found at the Riversleigh site in Northern Queensland. Hopefully Riversleigh will yield more platypus fossils. Andrew Taylor
sarima@tdatirv.UUCP (Stanley Friesen) (04/30/91)
In article <2347@cluster.cs.su.oz.au> andrewt writes: >The 110 million year date is correct (see Nature 318:363-366). Also in 1985 >a 15 million year old platypus skull (Obdurodon dicksoni) was found at >the Riversleigh site in Northern Queensland. Hopefully Riversleigh will >yield more platypus fossils. Thanks for the citation. I may even remember to look it up. [I am rather on the absent minded side]. I believe that the Riversleigh fossil was one of the 'sub-recent' fossils I had already heard about. (Well perhaps not quite sub-recent, but at least Neogene). The field of paleontology is really popping. It is getting really hard to keep up. Have you head about some of the incredible dinosaur finds of the last two years? By the way, does anyone know of a reliable mail gateway into Australia? I have yet to successfully get any mail through (the gateway I always get claims not to do international mail). -- --------------- uunet!tdatirv!sarima (Stanley Friesen)