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| Jaw Layout; just a short little observation. | |
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| Topic Started: Feb 6 2011, 05:01 AM (422 Views) | |
| Spugpow | Feb 6 2011, 05:01 AM Post #1 |
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If you're the kind of person who likes to follow a set of rules when designing aliens, I have another for you to tag onto the list: aliens descended from bottom-dwelling creatures with legs have jaws that open sideways, like an insect's. Obviously this is a vague guideline rather than a concrete law, but I think it will generally hold. This is because a.) leggy creatures will probably derive their jaws from legs, and b.) legs are bound to be arranged on either side of the organism's body (assuming bilateral symmetry), and not on its back and belly. Spoiler: click to toggle Exhibit A: a tiger beetle, descended from bottom dwellers with legs. Spoiler: click to toggle Exhibit B: a bobbit worm, displaying its leggy appendages and resulting jaws. And that's it. I feel a bit silly .
Edited by Spugpow, Feb 6 2011, 05:02 AM.
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| Spugpow | Feb 6 2011, 05:19 AM Post #2 |
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Oh, and heres a semi-related video of some African clawed frogs. Look at their front legs; they seem to be evolving towards jawhood. http://www.youtube.com/watch?v=DI9-iFlkGy8&feature=related Edited by Spugpow, Feb 6 2011, 05:20 AM.
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| Holben | Feb 6 2011, 12:05 PM Post #3 |
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The mandibles aren't derived from legs, all are derived from protrusion of the metameric segment which differentiate along their length. Paedialps, chelicerae are formed this way, and not developed from legs- just express the lengthening differentiation and make it spiky on the inside, no adaptation of legs needed! |
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Time flows like a river. Which is to say, downhill. We can tell this because everything is going downhill rapidly. It would seem prudent to be somewhere else when we reach the sea. "It is the old wound my king. It has never healed." | |
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| FallingWhale | Feb 6 2011, 12:57 PM Post #4 |
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Your basically saying that everything will turn its front legs into mandibles if it ever uses them in a way that could be considered superficially jaw like. |
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| Spugpow | Feb 6 2011, 12:59 PM Post #5 |
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This is from here: http://rstb.royalsocietypublishing.org/content/247/737/1.short "Mandibles are developed embryologically, and presumably phylogenetically also, in one or other of two ways. Type A, in which the biting structures are developed from a proximal endite or gnathobase (Crustacea, Chelicerata), and type B, in which the mandible is developed from a whole limb, the tip of which and not the base is used for gnathal purposes (Onychophora, Myriapoda, Hexapoda)." Granted, this paper is old, so old that Onychophorans are considered arthropods. Still, that shouldn't matter much (I think :P), since the topic is comparative anatomy rather than taxonomy. Anyways, it states that all arthropods have "biting structures" derived from limbs, but only hexapods' and myriapods' jaws are derived from entire legs. If I'm completely wrong about this, would you show me your source? thanks .Edit: No falling whale, I'm just saying that if a creature is going to have jaws, it might as well derive them from legs. There are obviously going to be many exceptions to this. The frogs probably won't take specialize their front legs any further, since they already have perfectly good jaws derived from gill arches. Edited by Spugpow, Feb 6 2011, 01:04 PM.
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| Holben | Feb 6 2011, 04:19 PM Post #6 |
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I may have generalised too far. Looking at things from 2D only brings trouble.Anyway, with some of them,. their ancestors had dozens of legs which become gnathobases which became mandibles. With others, atrophying legs became mandibles. But leg modification seems a common method. |
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Time flows like a river. Which is to say, downhill. We can tell this because everything is going downhill rapidly. It would seem prudent to be somewhere else when we reach the sea. "It is the old wound my king. It has never healed." | |
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| Ànraich | Feb 6 2011, 04:41 PM Post #7 |
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L'évolution Spéculative est moi
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Modifying limbs into mandibles works well for arthropods, being supported by an exoskeleton, but a frog? I doubt it. Arthropods generally have many, many legs, whereas a frog, being a tetrapod, relies on all it's legs and has none to spare. And fleshy legs supported by a skeleton are far harder to radically change. |
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We should all aspire to die surrounded by our dearest friends. Just like Julius Caesar. "The Lord Universe said: 'The same fate I have given to all things from stones to stars, that one day they shall become naught but memories aloft upon the winds of time. From dust all was born, and to dust all shall return.' He then looked upon His greatest creation, life, and pitied them, for unlike stars and stones they would soon learn of this fate and despair in the futility of their own existence. And so the Lord Universe decided to give life two gifts to save them from this despair. The first of these gifts was the soul, that life might more readily accept their fate, and the second was fear, that they might in time learn to avoid it altogether." - Excerpt from a Chanagwan creation myth, Legends and Folklore of the Planet Ghar, collected and published by Yieju Bai'an, explorer from the Celestial Commonwealth of Qonming Tree That Owns Itself
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| Spugpow | Feb 6 2011, 06:17 PM Post #8 |
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True Parasky, but the frog is completely aquatic, and so doesn't need its front legs for walking. To become better at chewing, they could develop bony spines or nubs like those of the spadefoot toad. I admit though, that having many legs to spare probably makes it more likely for some to be co-opted into jaws. |
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| Kamidio | Feb 6 2011, 06:43 PM Post #9 |
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The Game Master of the SSU:NC
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If the climate could permit it, I could see something like those frogs evolving into massive whale-like creatures. |
SSU:NC - Finding a new home. Quotes WAA
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| Ànraich | Feb 6 2011, 10:30 PM Post #10 |
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L'évolution Spéculative est moi
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Not really. It spends plenty of time out of the water too. Maybe not as much as a toad, but quite a bit. And exactly how does it not need its front legs for swimming? It doesn't exactly have fins to keep balanced. |
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We should all aspire to die surrounded by our dearest friends. Just like Julius Caesar. "The Lord Universe said: 'The same fate I have given to all things from stones to stars, that one day they shall become naught but memories aloft upon the winds of time. From dust all was born, and to dust all shall return.' He then looked upon His greatest creation, life, and pitied them, for unlike stars and stones they would soon learn of this fate and despair in the futility of their own existence. And so the Lord Universe decided to give life two gifts to save them from this despair. The first of these gifts was the soul, that life might more readily accept their fate, and the second was fear, that they might in time learn to avoid it altogether." - Excerpt from a Chanagwan creation myth, Legends and Folklore of the Planet Ghar, collected and published by Yieju Bai'an, explorer from the Celestial Commonwealth of Qonming Tree That Owns Itself
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| Spugpow | Feb 6 2011, 10:57 PM Post #11 |
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The frogs' front legs aren't too good for stabilizing; they're non-webbed (as you can see in the video). The frogs probably don't need much stabilizing because of their flatness. From here: http://en.wikipedia.org/wiki/African_clawed_frog The frog is indeed "completely aquatic" although it is capable of "traveling short distances between bodies of water". |
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| Holben | Feb 7 2011, 03:32 PM Post #12 |
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Rumbo a la Victoria
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Amphibious is a good word for that state! ![]() Tetrapod structure is far harder to change than that of arthropods, and bipedal frogs wouldn't be able to hop. Jaws in animals with an endoskeleton will most likely come from the skull, i reckon. |
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Time flows like a river. Which is to say, downhill. We can tell this because everything is going downhill rapidly. It would seem prudent to be somewhere else when we reach the sea. "It is the old wound my king. It has never healed." | |
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| Ànraich | Feb 7 2011, 04:59 PM Post #13 |
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No I'm telling you it is not completely aquatic because that implies it spend all its time in water. There are literal hundreds of frogs in my yard every summer, and I assure you that their front legs are indeed necessary. They do have to move to different sources of water every now and then, and since leaping is their only method of movement on land they need their front legs. I don't know about you, but when I jump or fall I use my legs or arms to keep me from landing on my face and causing serious injury. |
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We should all aspire to die surrounded by our dearest friends. Just like Julius Caesar. "The Lord Universe said: 'The same fate I have given to all things from stones to stars, that one day they shall become naught but memories aloft upon the winds of time. From dust all was born, and to dust all shall return.' He then looked upon His greatest creation, life, and pitied them, for unlike stars and stones they would soon learn of this fate and despair in the futility of their own existence. And so the Lord Universe decided to give life two gifts to save them from this despair. The first of these gifts was the soul, that life might more readily accept their fate, and the second was fear, that they might in time learn to avoid it altogether." - Excerpt from a Chanagwan creation myth, Legends and Folklore of the Planet Ghar, collected and published by Yieju Bai'an, explorer from the Celestial Commonwealth of Qonming Tree That Owns Itself
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Looking at things from 2D only brings trouble.



2:31 PM Jul 11