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Thread: Carnivorous Rodents

  1. #1 Carnivorous Rodents 
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    Hi

    I am designing some predatory rodents which I need some scientific fact to support the design of the teeth. As you can see the Rodent skull hasn't changed much for millions of years in fact they all look very similar.

    If let say Rodents are to become more effective hunters when kind of shape of their teeth they will need to adopt in order to make carnivorans make a run for their money?

    And also can a mammal's molar or incisor change shape if evolution allows?
    Example, a flat molar into a shearing knife edge

    Thank you


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  3. #2  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    Read this:

    Nature. 2007 Jan 4;445(7123):78-81. Epub 2006 Dec 13. Links
    High-level similarity of dentitions in carnivorans and rodents.


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    WYSIWYG Moderator marnixR's Avatar
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    Dougal Dixon's "After man" contains a predatory descendant of rats which he calls the falanx
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  5. #4 Re: Carnivorous Rodents 
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    Quote Originally Posted by ttyo888
    And also can a mammal's molar or incisor change shape if evolution allows?
    Example, a flat molar into a shearing knife edge
    This happened with our own ancestors. Unfortunately I was unable to find pictures of jawbones showing this.
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    Forum Cosmic Wizard paralith's Avatar
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    Actually, the teeth of folivores (leaf specialists) have high, sharp shearing crests. The mechanical difficulties of breaking down leaves is rather similar to those of breaking down meat. Frugivores have flatter, more rounded teeth - and, incidentally, one of the reasons why we can be fairly sure that early australopithecines didn't focus on meat eating was because they have the flatter teeth of a frugivore and would have had difficulty processing large quantities of meat.
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    Quote Originally Posted by marnixR
    Dougal Dixon's "After man" contains a predatory descendant of rats which he calls the falanx
    Hey, I've actually read that book. At the time I didn't think anyone else would actually bother. In hindsight it wasn't as pointless as I had first thought though.
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    But the teeth of Dixon's rodents seem a bit strange and based on my understanding that Rodents' teeth tend to keep growing on and on. Wouldn't the creature's so-call fangs overgrow?
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    Quote Originally Posted by ttyo888
    But the teeth of Dixon's rodents seem a bit strange and based on my understanding that Rodents' teeth tend to keep growing on and on. Wouldn't the creature's so-call fangs overgrow?
    Not if they regularly devour the skeleton as well, as I imagined they might do.
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    Well maybe... or they might scrap their teeth on tree like cats scratch trees

    Ok I managed to find something very similar to what I am looking for.

    The Thylacosmilus, a pouched sabre tooth from S. America. It's sorta like a rodent with long long teeth in a way.


    As you can see from the skull the creature lacks upper incisors and it's got only two canine that kinda look like the rodent's lower jaw. I wonder without upper incisors how does it eat?

    If someone can tell me how this creature eats maybe?
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  11. #10  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    Quote Originally Posted by ttyo888
    But the teeth of Dixon's rodents seem a bit strange and based on my understanding that Rodents' teeth tend to keep growing on and on. Wouldn't the creature's so-call fangs overgrow?
    The typical formula of rodents is a continuously growing incisor (2 upper and 2 lower ones), followed by a diastema region (toothless region), and a row of molars. (so no canines and premolars).

    The incisors are continuously growing and possess a shelf-sharpening edge, due to the harder enamel on one side of the tooth and softer dentin on the other side.

    Of some rodent species also the molars are continuously growing, such as for instance the guinea pig and Microtus levis.

    Many voles also have high crowned molars.

    Of course you never bothered to check out the article I referred to, but it has all the information you need.

    To test our prediction we measured cheek tooth complexity in two mammalian groups, carnivorans and rodents.
    We used five dietary categories to classify the species in this study, in order of increasing processing demands on the teeth: hypercarnivore, carnivore (including insectivores), animal-dominated omnivore, plant-dominated omnivore, and herbivore (specifically stem and leaf feeders, composed of grazers, browsers and mixed feeders). Whereas both mammalian groups show considerable overlap in dietary specializations, rodents lack hypercarnivores (that is, dedicated vertebrate flesh eaters) and carnivorans have few taxa in the plant-dominated omnivore and herbivore categories.
    Basically what they discovered was that teeth get more complex in shape from carnivore to herbivores. In principle the nature of the complexity doesn't matter, it just constitutes an increase in edges and surfaces.

    That's because grinding tough food requires more surfaces/edges rubbing against each other.


    Rodents have no trouble eating meat. They eat their own puppies all the time.

    A specialist rodent carnivore, or hypercarnivore will simply have simpler molars.

    That's because incisors do not vary in occlusal complexity between rodent species.

    And they cannot vary either because of developmental constraints.
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    Quote Originally Posted by ttyo888
    i'd say a more apt simile for a specialist carnivorous rodent dentition might be Thylacoleo - look at the blade-like molar



    alternatively, you do have some multituberculata such as Ptilodus who have blade-like molars

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    Hmmm looks like the incisors do not have to change just make them big I think

    But the Molars will have to turn into slicing teeth then.

    Great... so I think the my carnivores will have an add advantage over lions,tigers and leopard. If meat is off the menu, well nothing is going to stop them from eating plants. Sounds funny, it's like looking at a lion tucking in to vegetables...
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  14. #13  
    WYSIWYG Moderator marnixR's Avatar
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    besides, many members of the order Carnivora are not strict carnivores - the cat family is the most exclusively carnivorous, whereas many of the dog and bear families are far less so

    presumably the reason why Dixon chose rats for his evolutionary thought experiment is that they are by far the best-known omnivores amongst rodents
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  15. #14  
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    Incisors (lower incisors) are already huge motherfuckers in rodents. They run from the back end of the jaw all the way to the front and then stick out for a considerable length. And they are razor sharp.
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  16. #15  
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    Quote Originally Posted by spuriousmonkey
    Read this:

    Nature. 2007 Jan 4;445(7123):78-81. Epub 2006 Dec 13. Links
    High-level similarity of dentitions in carnivorans and rodents.
    Ok oh yeah spuriousmonkey, I think I owe you an apology for not looking at the article you referred me to, I googled the article only to find nothing but just a small paragraph with useless information

    but I thanks all of you for your insights.

    And also the speed of a Rodent tooth growth is variable right? I think my rodent would have teeth had grow slightly slower.
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  17. #16  
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    The growth rate is a bit variable. Also dependent on the wear.

    The thing is that rodent incisors are really continuously growing. Growing them longer without wearing them down will only cause problems. Like having your teeth curve around to grow in your brain.

    Large canines (which rodents don't have) aren't a necessity for a predator dentition.

    The rodent incisors are basically already two clamping sharp chisels.

    With shearing molars you are already quite far. Maybe you can also look into other adaptations such as the nails. Let them have strong and long claws for grasping. A killer incisor bite due to sharpened incisors (normal) and a powerful muscular bite.

    Then shearing molars for cutting up meat.

    It could use its incisors for gnawing open long bones and such to get to the nutrition rich marrow.

    The dentition of rodents is already flexible. Just make the other adaptations more prominent that lie outside the dentition. Strong sharp nails. Enlarged jaw musculature for that killer bite that doesn't let go. It also allows for eating bone.

    An enlarged brain?

    Maybe the animal itself should be enlarged. Make it seem like a giant rat on steroids with an apetite for beef.

    A smart opportunist. With chisels for teeth.

    /shivers
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    I'd just like to add that large canines seen in predators like big cats are for a specific type of hunting strategy - they pierce into the flesh and then stay there, allowing the hunter to clamp down their jaw and hold. Big cats often do this on the necks of their prey to effectively strangle them to death.

    Some primates have large canines as well, like baboons, but they're for a different purpose and also have a different structure. Baboons use their canines to fight with each other, not to hunt. The back side of baboon canines are sharp like a razor, they're not conical like big cat canines. Baboons use these canines to slice up their competitors in fights, and leave big long gashes that are more likely to get infected.
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  19. #18  
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    Quote Originally Posted by spuriousmonkey


    Maybe the animal itself should be enlarged. Make it seem like a giant rat on steroids with an apetite for beef.

    A smart opportunist. With chisels for teeth.

    /shivers
    I see...

    Thanks! you are a great help to a me, budding CG artist! And of course my "rodents" are pretty big, Capybara size is very common in my case. and Scavengers can vary in size from hamster to hyena. Predators are an enigma indeed, they can be tiger sized but as I mentioned earlier, they can on one hand eat a horse and next nibble a few leaves like vegatables with your meat.

    But hey is it a bit absurd for the rodent's teeth go into something like this?
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  20. #19  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    The problem with rodent incisors is that they really need to have proper occlusion. The way they are 'designed' determines that lower and upper incisors need to wear each other down.

    The 'front' (or labial side) is covered with enamel normally found on the crown. That's why is often called 'crown analogue'. The back (lingual side) is covered with softer dentin (a bit harder than bone), and called 'root analogue'.

    Upper and lower incisor will slide over each other. The hard enamel edge will wear down the dentin faster than the enamel of the opposing tooth. This will create an edge. A sharp edge.

    In the picture you have the incisors protruding. Occlusion will be lost. That is not good. Also the developmental aspects are a bit shaky.

    First of all the differential growth between lingual and labial side means that the incisor has a curve.

    Secondly, the upper incisor grows downwards, not forwards. It will be very difficult to change this developmentally speaking.

    Thirdly, I see that the specimen in the picture is eating a worm. Carnivorous rodents already exist. That is carnviorous rodents eating invertebrates such as insects and worms. They do not need a specialization of the incisors at all. It's all about the molars.


    On another note, the predator could also be a group predator. In that way it could remain smaller.
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  21. #20  
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    I see

    Well basically I have trying to get creative and see if I can reduce the dention to the point it can lighten the head for flight. But I think maybe it doesn't need that "beak".

    But then again, my rodents have a flying branch that are somewhat a hybrid between mammal and pterosaur, they used all four limbs in take off and flight.
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  22. #21  
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    The skies are already filled with flying 'shrews'. Or should I say shrew-like animals.

    BATS....

    Of course their dentition is radically different from rodents. Like shrews.

    But an insectivorous rodent is rather similar to an insectivorous shrew. Just not dentition formula wise.

    The rodents are stuck with their continously growing incisors.

    They are stuck with their diastema region (so no canines and premolars). There are vestiges of these teeth during early development, but their development gets stuck on a really really early stage.
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    [quote="spuriousmonkey"]The skies are already filled with flying 'shrews'. Or should I say shrew-like animals.

    BATS....

    quote]

    Well Shrews never got onto offshore islands without human intervention but my island got rodents becos some 10 million years ago some freak flash flood brought them by driftwood. Then they decimated the avian inhabitants to extinction and took over.

    Bats are good at flying but they suck at reproduction compared with rodents. Rodents have a good talent at multiplication which I dun need to emphasize how it takes two rodents one male one female to turn my house upside down.
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    But then the beak thing in Dixon book might still work if it modified correctly

    Take a look at this Naked Mole Rat
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  25. #24  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    It uses his teeth for digging.

    So they actually grow through its lips so that the dirt doesn't enter his mouth.

    You can still see how the upper incisors actually grow downwards, and the lower incisors grow forward.
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