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| Ectothermic Mammals; mammals that lose endothermy | |
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| Topic Started: Jul 25 2010, 10:48 PM (1,881 Views) | |
| Toad of Spades | Jul 25 2010, 10:48 PM Post #1 |
Clorothod
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Since crocodiles started as endothermic creatures and lost their endothermy as they adapted to their lifestyle, how likely do you think it is that mammals could produce such a metabolism if the need arose? Also what other lifestyle could produce ectothermy in mammals besides the crocodile-like niche? I think its highly likely that if the need arose, it could happen. With early crocodiles being "warm-blooded", there's no significant reason why mammals can. As for a niche besides the crocodile-like niche, maybe the super-low energy lifestyle of the sloth could produce something like a sloth-like creature with the metabolism of an herbivorous lizard. |
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| Pando | Jul 26 2010, 01:27 AM Post #2 |
Obey or I'll send you to the moon
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Shrews are pretty close to becoming cold blooded, I've read. |
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| Carlos | Jul 26 2010, 03:51 AM Post #3 |
Adveho in me Lucifero
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I think ectothermic mammals are more likely to evolve on islands, since food is scarcer there. The extinct Myotragus from the Balearic islands proves an example of an island endemic mammalian ectotherm |
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| The Dodo | Jul 26 2010, 04:57 AM Post #4 |
Prime Specimen
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Maybe one could evolve in a desert as well, I think it's some kind of desert rodent that can lower it's body temperature and rely on outside heat to warm it up. |
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| Toad of Spades | Jul 26 2010, 02:05 PM Post #5 |
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Clorothod
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THAT'S INCREDIBLE!!! I had no idea that something like that even existed! I bet seeing them moving would be pretty odd. I wonder what they would evolve into if they didn't go extinct and were introduced onto a small yet slightly larger island with reptilian predators. |
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| Ook | Jul 26 2010, 03:18 PM Post #6 |
not a Transhuman
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what do you think?they will propably stay in same form |
   
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| Carlos | Jul 26 2010, 03:18 PM Post #7 |
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Adveho in me Lucifero
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Myotragus was, in appearence, an average caprine (sans the foward pointing eyes), so it probably moved just like a goat, but certainly was more lethargic, being slow most of the time but presumably capable of short bursts of speed to avoid birds of prey, the main native predator of that ecosystem Edited by Carlos, Jul 26 2010, 03:19 PM.
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| lamna | Jul 27 2010, 06:02 PM Post #8 |
 
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I think it's quite probably that some mammals will "lapse" back into cold bloodedness. But I doubt it''s going to be any more than a evolutionary dead end. |
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| Toad of Spades | Jul 29 2010, 01:45 AM Post #9 |
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Clorothod
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Maybe endothermy could help during another severe mass extinction, escpecially if its a small omnivorous form, maybe a small ectothermic shrew. The low demand for food could give them an advantage over endothermic mammals and enable to survive. |
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| Ook | Sep 2 2010, 08:00 AM Post #10 |
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not a Transhuman
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just something that i found on net,its about mentioned myotragus Myotragus Myotragus balearicus (in Greek, "goat-rat of the Balearic islands") is the scientific name of a species of the subfamily Caprinae who lived in the islands of Majorca and Minorca until its extinction does about 3000 years. Although the last genetic analyses made in the University Pompeu Fabra have been described to it like a strange goat, indicate that Myotragus was more closely related with sheep. Description The first that calls attention of this animal is its head. The eyes were not directed towards the sides, as it happens in all the herbivorous mammals, but towards the front, granting them a stereoscopic vision (with all probability, their vision (=vista) was its main sense). The inferior jaw rarely contained two incisors of continuous growth (as it happens in the rodents and lagomorphs, but in the ungulates), while that the superior one lacked them. The rest of teeth were molars and premolars adapted to the crushing of vegetal matter. The nose was short in comparison with the rest of the skull, giving him slight similarity with rabbits and hares. Finally, both sexes displayed at the top of the head two very short horns, although probably the corneous covering made more lengths enough than the bony bases. Myotragus was quite small in size (about 50 centimetres) and weighed between 50 and 70 kilos. The legs were proportionally shorter than in other related and less flexible bovids, which did not have to make them exceptionally fast. This was not a serious problem because on the islands where it lived, predators did not exist except for some birds of prey, to which without a doubt would try to give esquinazo hiding itself between the vegetation before by means of the fled one. On the shoulders they had a pronounced hump, whereas the back was bent in the back quarters. The legs, like many from the artiodactyla order, had four fingers of which only two were used to walk. The tail was enough long in relation to the rest of the body. Feeding The fossil and subfossil remains of Myotragus balearicus indicate with total security that this animal was a ramoneador, like the present goats. One fed on all class of arbustiva vegetation and low branches of the typical trees of the Mediterranean climate, although it felt a special predilection by the Balearic shrub. The deposits of Majorca and Minorca, as well as the absence of pastadores (maybe grazing??) animal, seems to indicate that the primitive Balearic island were covered totally by forests before the human poblamiento and that herbaceous prairies of appreciable size did not exist. In this atmosphere, the Myotragus would move of preferably solitary form or in small groups. Reproduction Great thing is not known on the reproductive habits of this species. In 1999 the skeleton of a found neonato (neoborn, recently born??) individual near Manacor was described , to the northeast of Majorca. One is a quite great young in relation to the size of the mother, that it could walk and already follow his progenitor soon after being born. It is probable that it did not take long time in maturing, perhaps only a year or two. The fact that the species conserved the horns is a possible indication that the males used them to fight by the right to reproduce, but the lack of sexual dimorphism invites to think that this species was not polygamous or, at least, the males did not reunite "harems" after them. Given the little length of the horns, the combats, in case of taking place, they had to go more towards the flanks (as it happens in many small antelopes) than to the fight head against head (typical of ungulates of great size). The Mediterranean climate is seasonal, reason why it is of supposition that the mating would not happen at any time of the year. Origins The unique characters of Myotragus balearicus are consequence of a prolonged process of evolution in conditions of insularidad. In this type of isolation, the ungulates tend to become smaller (erosive and lagomorphs, on the other hand, they increase of size, as it happened to Hypnomis, the giant dormouse that shared habitat with Myotragus) and to lose the fear and reaction to flee from predators. A clear example of this is the loss of capacity of the legs to run at high speed, the stereoscopic vision (useful to calculate distances, but it does not stop to discover enemies on the lookout) and the proportional reduction of the brain, something that has also been observed in Homo floresiensis, a newly discovered hobbit-like human species on the island of Flores, Indonesia. The analyses of DNA and the oldest fossils (Pliocene 5.7 million years ago) of the island of Majorca (Myotragus pepgonellae) indicate that Myotragus balearicus, in spite of being a ramoneador animal, descended originally from pastadores. The closest related species to Myotragus are ovine like the extinct Nesogoral of the Plio-Pleistocene of Sardinia, the old Gallogoral of France (possible continental ancestor of Myotragus and Nesogoral), Ovis (present sheep and mouflon) and mountain goats of Central Asia. Last common ancestor common Myotragus and Nesogoral had to arrive on Majorca and Sardinia about 6 million years ago, time at which the Straits of Gibraltar was closed and the Mediterranean Sea was dried until being reduced to a few salty lakes. Later, the reapertura of the Straits and the massive salt water entrance isolated to the animal populations diverse in the new Mediterranean islands. Of parallel form, a climatic change replaced the vegetation of subtropical type by the present one of Mediterranean type, forcing to the Myotragus to develop drastic changes in its feeding and set of teeth. Although it turns out strange to say it, Myotragus only colonized initially the island of Majorca. On Ibiza a strange fauna without terrestrial mammals was developed where the birds and bats were the main vertebrates, whereas in Menorca a giant rabbit evolved that covered the same niche that the Myotragus in Majorca. With the slope of the level of the sea in the Glacial Era, Majorca and Menorca were united and Myotragus replaced the great lagomorphs Minorcan. Both islands separated again at the beginning of the Holocene. Extinction The diverse dating indicate shortly before that the three native terrestrial mammals of Majorca (Myotragus, Hypnomis and musaraña giant Nesiosites) disappeared in a same period of very short time, during the third millennium before Christ. During years of continued discussion between scientists, some say the extinction was caused by climate change, others say they were exterminated by the first human settlers of the Balearic Islands. Sometimes evidence appears that could support both opinions differently. That is also why the question is still not answered. The main thesis is the one that aims at an extinction by antrópicas (human, antromorphic???) causes. Tradidional methods had dated the first human colonization of Balearic towards the 5000 AD or even before, but the revision of the deposits with modern methods of dating indicates clearly that there was no human presence before 3000 AD, reason why the first Balearic ones would be the carriers of the pre-talayótica culture (3000-1400 AD). The date is, of course, really suspicious, because lapel very closely with the fast decay of the three species. The first Balearic settlers had a Neolithic culture, although they continued living in caves. In these have been found enormous amounts of bony remains of animals, especially Myotragus, with signals evidence of carving and consumption by humans. Most surprising it is that not all Myotragus arrived dead at the caves, but that there are indications that many of them were kept alive during a certain time there, and also many of them have the horns trimmed and healed later: A clear indication that they were being object on an attempt of domestication. The reason for this failure to domesticate it is probably that Myotragus did not reproduce in captivity or not at an suitable speed, because in the caves only remain of adult individuals have been found. The hunting, the failure of the domestication and the introduction of domestic animals like goats (that competed with Myotragus for the same food), cows and sheep (and consequently, the destruction of the forests to create places for them to pasture) and dogs and pigs (which they could depredate on Myotragus in case of asilvestrarse itself) were the probable causes of the extinction of this animal. Edited by Ook, Sep 2 2010, 08:01 AM.
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| Practically Uninformed | Sep 2 2010, 09:40 AM Post #11 |
Informed enough to care
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Doesn't seem to say much about its ectothermy. |
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| Carlos | Sep 2 2010, 04:18 PM Post #12 |
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Adveho in me Lucifero
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It came in an article that wasn't included on the Wikipedia page, naturally (the posted info comes from there) |
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| The Dodo | Sep 2 2010, 04:42 PM Post #13 |
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Prime Specimen
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Here's an article about it's metabolism http://www.physorg.com/news177755291.html |
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7:37 PM Jul 13