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| Metatherians vs Eutherians | |
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| Topic Started: Apr 24 2009, 10:30 AM (1,438 Views) | |
| Carlos | Apr 24 2009, 10:30 AM Post #1 |
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Adveho in me Lucifero
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This topic might fit better in the future or alternate evolution categories, but nonetheless I'd like to discuss this (specially with Paralith, and anyone else that takes this seriously). As a whole, marsupials, when competing against placentals, seem to loose. However, in most of these cases changes in climate and other things were always added to the mixture, and I wonder if the results could had gone differently, or if marsupials could happen to become more diverse in the future. AFAIK the only niches marsupials seem to hold well against their eutherian cousins seem to be arboreal ones, for we have opossums in the americas and some sort of possum in Sulawesi; in both places, placentals are present. However, other metatherians (marsupial or not) seem to loose; for instance, we have shrews in western and northern South America and only small marsupial insectivores along the Andes. On the other hand, we do have shrews in Oz (I doubt they were introduced, since shrews don't go hiding in ships like rats do) and yet their marsupial analogues seem to be doing fine, though that might just be because shrews got in recently. However... ...we also had Tingamarra in Paleocene/Eocene Australia, and yet marsuials prevailed and no whatever-Tingamarra-was were found after the Eocene, implying that marsupials won over placentals in the evolutionary battle. This is all very weird, but the decline of american metatherians might just be because South America was victim of an asteroid impact during the Pliocene, allowing the placentals to conquer while marsupials were still recovering. And yet, there were metatherians in Eurasia (no one knows if they were true marsupials or not), and yet they quickly declined after the Oligocene, with the last ones dying without any explanation in South Asia during the Miocene/Pliocene boundary. This confusion might seem pointless to debate, but actually it is, because we can thus know if marsupials can become more diverse in the future in the Americas (like the Neocene's marten possums, which took over carnivore niches), or if aussie marsupials will be reduced to nothing but the arboreal possums and perhaps some wallabies. So, anything on the matter? |
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Lemuria: http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/ Terra Alternativa: http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/ My Patreon: https://www.patreon.com/Carliro ![]() | |
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| ATEK Azul | Apr 25 2009, 12:41 PM Post #2 |
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Transhuman
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this is an interesting topic. i could see metatheriums taking over but for some reason everybody doubts it. |
| I am dyslexic, please ignore the typo's! | |
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| ashwinder | Apr 25 2009, 07:01 PM Post #3 |
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Adolescent
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It's just that the marsupial reproductive formula is a bit of an iffy one. They reproduce far less frequently and have higher infant mortality due to the complexity of raising such an immature infant externally. |
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| ATEK Azul | Apr 25 2009, 07:26 PM Post #4 |
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Transhuman
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true maybe if they evolved a different reproductive system? |
| I am dyslexic, please ignore the typo's! | |
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| Carlos | Apr 26 2009, 02:54 AM Post #5 |
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Adveho in me Lucifero
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Kangaroos, though, seem to be like marsupial rodents; they can have three kids at the same time. And they don't come all at the same time; first, a mother is raising a joey that already has left the pouch, as well as another still developing and one (under the form of an undeveloped embryo) still waiting to come out once she can have the means to raise it. The main issue of metatherian reproduction seems quite obvious in the water; because of the risk of the pouch getting flooded, few marsupials have taken aquatic niches. However, the yapok has pouch muscles that close the pouch in the water. Also, the environment inside the pouch is warm and wet, so if the female had the interior side of the pouch very rich in capillaries the oxygen concentration there could even be bigger than outside and she wouldn't have to abandon the water. But such hasn't yet evolved |
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Lemuria: http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/ Terra Alternativa: http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/ My Patreon: https://www.patreon.com/Carliro ![]() | |
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| ATEK Azul | Apr 26 2009, 11:37 AM Post #6 |
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Transhuman
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interesting. thats all i have right now lol!! |
| I am dyslexic, please ignore the typo's! | |
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