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Terra Mollusca; Because Terra ____ names are fun.
Topic Started: Apr 8 2011, 01:10 AM (1,578 Views)
Cephalian
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So finally decided to type this up: an alternative to Earth's evolutions, where Mollusks have made all of chordata an evolutionary footnote as opposed to the dominant life forms. This takes place about 200 million years after Mollusks first progressed from the ocean to the land. Why they beat out chordates is something I will explain in a later post - an accidental refresh deleted that information and I don't feel like fully retyping much of it.

It's worth noting that much of Mollusk anatomy is still present, especially the structure of the central nervous system, which forms a ring around the throat as opposed to it's dorsal location in most chordates, and radula as opposed to the tongue we are more familiar with. Further similarities will be elaborated upon in a later post, including how they developed skeletal systems and how they are able to breathe in air.

If you haven't read up on it, there's some major barriers to mollusks being the dominant life form. The primary one is the lack of a skeletal system - the primary means of movement for mollusks is a single, muscular "foot". I've read several discussions as to why this foot is so poor for terrestrial movement, because it either requires a large amount of water lost to create a slime to "slide" on - great in swampy or costal areas, but still incredibly slowly and wasteful in most environments – or tentacles, which are absolutely horrific for terrestrial movement. This would require the development of some sort of skeletal system - as cool as tentacles look, they're horrific for terrestrial movement. The argument has been made that evolution doesn't make things, merely works with what's there. The result of this is 3 Superclasses of Mollusks – those whose shell developed into their current skeleton, those who calcified bones, and those that only have a weak cartilage skeleton to allow shape to be maintained but have figured out how to use their “foot” or tentacles for terrestrial movement. I'll elaborate on these superclasses later, but cannot work up the energy to retype that right now.

Instead I'm going to take a moment to look at one of the creatures of Terra Mollusca – an ambush predator that fills the same niche alligators fill on modern earth, called the Swampgrasp. Again, lack of energy keeps from further details right now, but I want to get the ball rolling on this.

Swampgrasp
The Swampgrasp has a long, sinuous body with out much distinction between torso and “tail” (actually a branch of the foot they once had.) The rear 3 pairs of “fins” are supported by an overall skeletal structure and allow for propulsion in water and, like the forelimbs of a sea-lion, crude movement on land. The forward 2 pairs of limbs are stronger, segmented grasping two toed claws, used less for hunting and more for aquatic territorial disputes. Their eyes are located on long stalks, allowing either binocular vision above or below the water, or monocular vision in both locations simultaneously. They change their coloration to best fit into their environment, looking more like logs or other aquatic debris in most situations.

What makes the Swampgrasp unique is how members of their genus hunt. The front of their head is a large, blunt beak that conceals their true weapons – a radula that branches into three semi-prehensile psuedo-radula. Upon finding prey, the swampgrasp will swim within range before using powerful muscular action to launch all three psuedo-radula at their target and attempt to grab onto it – something the serrated edges of the radula makes possible more than their inherent strength. Once caught, the swampgraps will attempt to drag its prey wholly into its large beak or, if the prey proves to be too strong, moving onto land to consume the creature there. Once inside the beak, the radula begin undulating to “shred” the creature into something more easily digestible. They are strong enough to even “saw” through the skeletons of most creatures, meaning the entire prey is digested.

So there you have one of the predators of Terra Mollusca and some of the science behind it, something I fully intend on elaborating on in the coming days. Still, I hope you enjoy.
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Also, I apologize in advance to sometimes responding to quoted posts separately, my iPad makes it nearly impossible to multi-quote multiple posts.
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urufumarukai
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I was just about to post somthing like this.
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Cephalian
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The overall concept or the particular creature? Either way, convergent speculation once again! I hope you don't stop from making your thread because of mine, I'd love to see what you come up with.
Check out my settings, either Urban Jungles or Terra Cephalapodia!

Also, I apologize in advance to sometimes responding to quoted posts separately, my iPad makes it nearly impossible to multi-quote multiple posts.
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Canis Lupis
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Dinosaurs eat man, woman inherits the Earth.

So how much information on making cephalopods terrestrial would you like me to disclose? I know you said you wanted to go about this on your own for a bit just to study the process of convergent speculation, so I want to know to what degree I can help you out with this, seeing as I have my own idea for a mollusk ruled world.

Anyway, the swampgrasp. I'm assuming it's descended from a gastropod, right? Particularly some sort of slug?
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Empyreon
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Are you plausible?

I love the swampgrasp! I've never thought of a mollusc in the crocodile's niche. I too want to know whether it developed from gastropods or cephalopods. The indication of a "foot" points to gastropod ancestry, but the shape/color changing is reminiscent of cephalopods; is that camouflage trait an inherited artifact or a case of convergent evolution?
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food for thought
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Canis Lupis
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Dinosaurs eat man, woman inherits the Earth.

Well remember Empy that cephalopods also have a foot, though it's harder to see it as a foot since it is split into so many different tentacles.

But I agree. Very interesting choice.
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Empyreon
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Are you plausible?

That's very true, but the description talks about an ancestral "foot"-- singular. It doesn't say "feet" or "foot-turned-tentacles". It's an interesting mystery about the evolutionary lineage, that's all. :)
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food for thought
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Cephylus
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I absolutely love the Swampgrasp as well, interesting how the radula is used as an ambush predatory weapon. Never thought a radula could specialize for such uses. Nice job!

The introduction on the evolutionary history of the chordate mollusks give a feeling of a more gastropod ancestry rather than a cephalopod one, but I dunno, unless the gracious Cephalian plans to elaborate more soon, we'll have to wait.

The geological period, I guess, is about Carboniferous~Earliest Permian? Are the conditions same? And outside of chordates and mollusks, are there any other groups that come into the scene? Arachnids, echinoderms and such?
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Let the art projects commence with the piling up!!!
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Wonderful, my friend the english major. It kinda shows the way you write. What will the flyers be?

And will you have art? :glare:
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Cephalian
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So how much information on making cephalopods terrestrial would you like me to disclose? I know you said you wanted to go about this on your own for a bit just to study the process of convergent speculation, so I want to know to what degree I can help you out with this, seeing as I have my own idea for a mollusk ruled world. Anyway, the swampgrasp. I'm assuming it's descended from a gastropod
right? Particularly some sort of slug?


My next post here (later today) is going to go into my ideas for mollusk locomotion overall terrestrial, if you could share some information after that I'd really appreciate it – especially if I get things horribly wrong.

And yes, the swampgrasp and all other creatures with trisected radula belong to the same class, one that evolved from a large slug. I considered a cephalopod as the basis, but realized if tentacles were already there that the radula would never evolve that way – why make new weapons when you can just use the ones you have seems to be evolution's motto in cases like these.

Empyreon
 
I love the swampgrasp! I've never thought of a mollusc in the crocodile's niche. I too want to know whether it developed from gastropods or cephalopods. The indication of a "foot" points to gastropod ancestry, but the shape/color changing is reminiscent of cephalopods; is that camouflage trait an inherited artifact or a case of convergent evolution?


Thank you! And, it's a gastropod with the camouflage as a case of convergent evolution – we know mollusks can “figure out” to do that biologically, and in a terrestrial environment where sight becomes much more important due to view distances, the ability to evolve this is a huge one, especially for many prey animals and ambush predators.

Canis Lupis
 
Well remember Empy that cephalopods also have a foot, though it's harder to see it as a foot since it is split into so many different tentacles.

But I agree. Very interesting choice.


y'all keep up this praise and it's gonna swell my little old ego.

Cephylus
 
absolutely love the Swampgrasp as well, interesting how the radula is used as an ambush predatory weapon. Never thought a radula could specialize for such uses. Nice job!

The introduction on the evolutionary history of the chordate mollusks give a feeling of a more gastropod ancestry rather than a cephalopod one, but I dunno, unless the gracious Cephalian plans to elaborate more soon, we'll have to wait. 

The geological period, I guess, is about Carboniferous~Earliest Permian? Are the conditions same? And outside of chordates and mollusks, are there any other groups that come into the scene? Arachnids, echinoderms and such?


Thank you as well! And yes, it's Carboniferous, on that edge where it could be considered Permian. Conditions are the same overall – there hasn't been enough time for the different life forms to radically alter the ecosystem. Almost all non-chodates come onto the scene, especially the arthropods – though they're going to take some very interesting forms to deal with their new neighbors.

Jasonguppy
 
Wonderful, my friend the english major. It kinda shows the way you write. What will the flyers be?

And will you have art? 


My ego, it grows so large! The flyers are going to be interesting – I have some ideas on how that could work, but need to hammer out a few details. They're likely going to be a gastropod evolution as well, though one that figured out another trick from the cephalopods (there's a slight chance I might decide a cephalopod descendent could fill this niche better, gonna have to work on it. And as for art:

Sabrwolf
 
Let the art projects commence with the piling up!!!


As much art as he feels like making is your answer. ;)

BTW, Sabrwolf, the Swampgrasp directly came from that discussion we had the other night about various mammals filling the rivershore ambush predator niche.

Coming up next will be a discussion on how mollusks became terrestrial, and at least one new creature – the favored prey of the swampgrasp.
Check out my settings, either Urban Jungles or Terra Cephalapodia!

Also, I apologize in advance to sometimes responding to quoted posts separately, my iPad makes it nearly impossible to multi-quote multiple posts.
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SabrWolf
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I have a preliminary sketch of the Swampgrasp! However, I'm not posting it yet. I need more information to make it look less... sluggy and more... swampgraspy. lol
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Cephylus
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Nice. :) Looking forward to the update. So if mollusks replace all chordates, I'm guessing that there are sea-going mollusks as well?
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SabrWolf
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So if mollusks replace all chordates, I'm guessing that there are sea-going mollusks as well?


I don't think that the chordates are ALL gonna be gone. Evidence:

Cephalian
 
Mollusks have made all of chordata an evolutionary footnote as opposed to the dominant life forms


I think that what Cephalian was saying here was that Chordates and Mollusks have essentially switched places in terms of where they stand in the "Dominance Scale" of the Earth. So the Chordates are still around, but they inhabit niches similar in both importance and scale as the Mollusks do today on our Earth.

EDIT: Correct me if I'm wrong however; as I could be completely off base here. lol
Edited by SabrWolf, Apr 9 2011, 09:32 PM.
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How Mollusks Got On Land

This is the biggest struggle for Terra Mollusca, and one I've spent a decent amount of time working on. I've come up with the following to explain how mollusks learned to move on land.

First of all, it does vary on what type of mollusks we're talking about. How a Nautiloid progresses to land is different from how a squid would which is different from how a gastropod would which is different from how an octopus would. However, there are some commonalities in problems.

1) Mobility: Using a singular muscular foot, or a muscular foot that's advanced into tentacles, works on land. Poorly. Just watch a snail or a video of an octopus that's escaped it's tank - slow, awkward, slithery at best. This foot works great in an aquatic environment, but that's because water is 27 times denser than air...a problem which leads to the second difficulty

2) Support. The closest thing any mollusk has to a support structure that goes beyond muscles is the external shell found in some. Neither of these is effective at all at supporting a larger creature in a terrestrial environment with anything resembling some real shape. It's important to note that solving this problem goes a long way to solving the mobility problem.

So let's look at support first.

NOTE: I'm writing this in a hurry to get some information for Sabrwolf to use for artwork - I'll be posting a greater detailed description tomorrow with a focus on how these things evolved and a few other methods of locomotion that developed.

Mollusks in general have some unique advantages when it comes to evolution. Lacking a clear support system, while a hinderance on land, is an advantage evolutionarily because it "costs" much less to have a variety of muscle structures than it does a variety of skeletal structures - there's a reason no tetrapod has ever evolved an extra set of limbs, and that's because of the amount of difficulty in doing it from an evolutionary standpoint without it being a hinderance for awhile (three legged frogs rarely do well). So the support structure started with the development of two things - the foot moving into various shapes and sizes, and a crude skeletal structure forming. I'll get into more overall detail later, but I want to focus for a moment specifically on how the swampgrasp's skeletal structure works.

The gastropod the swamp grasp evolved from was a slug and lacked any kind of shell - there was nothing existing hard for evolution to work with. So what happened is a process that occasionally occurs in humans - ossification of muscles. For humans, it's a horrific, fatal condition. For the swampgrasps ancestors, it was a blessing. An internal "shell"formed, a series of subcutaneous interlocking plates that did not pose much of a limit on mobility, connected by flexible musculature and ligaments each one. Once that was formed, it gave evolution something to work with. The forelimbs - the grasping claws - of the swap grasp are common among creatures it shares an evolutionary ancestry with. These were branches of the foot that a skeletal system gradually filled, starting with a series of what amounted to interlocking ball-bearings and going from there to 6 longer, connected bones that fit together with a ball-structure. They are connected to the back plates by similar sockets, giving them a great range of flexibility. Like most evolved gastropods, the rest of it's support structure - ribcage especially - is formed from cartilage as opposed to ossified muscles, meaning it can squeeze through surprisingly small spaces - and giving it a great deal of flexibility, part of why it typically floats upside down when imitating a log. The rear fins have no skeletal backing, having evolved once the swamp grasp returned to an aquatic environment, and are pure musculature.

Another form of support came from another source - a primitive version of the octopus. In addition to normal respiration, they can take in water and, using an electric charge like the one generated by certain eels - break water into it's component atoms. The oxygen extracted from water is not usable for respiration, though it does increase overall global oxygen levels once it combines with another to form O2. The H2 left behind by the process is the useful bit - it fills large sacks on it's back with the H2, not enough to truly allow it to fly but enough to make it light enough where no skeletal structure was needed to allow for terrestrial mobility. (The other idea I had for doing that was the creature generating enough internal heat to create a "hot air ballon" effect, but I'm not sure which is more likely - at least this idea uses a mechanism found in evolution, the generation of electrical current.)

However, these hydrogen ballasts are extremely fragile and the creatures that evolved this are quite slow and must have a constant source of water and consume a great deal of food - it's unlikely many of them will survive any major extinction event.

For now, though, they do exist, resulting in the favored pray of the swampgrasp: the floatapus.

Floatapus:
Physically they're fairly easy to describe. They look like octopuses with two huge, fragile balloons attached to the head directly behind the eyes, climbing across the land on their 8 tentacles. They're omnivores in the truest sense - there is very little they do not at least attempt to eat, aside from stone. The electrical charge is built up in the same way an eel builds up theirs, generated from the movement of muscles through special organs in the tentacles, which does thicken and limit their tentacle's mobility. Discounting the ballons, they're fairly small - about 1 from head to tentacle tip when stretched to max height - but the balloons literally double their size.

The swamp grasp favors them as foods because all it needs to do with it's initial salvo is puncture just one of the balloons - at that point, it can no longer support its own weight and becomes simple to catch and eat.

But they are not defenseless. Even discounting the strength of their tentacles, a floatapus caught with it's balloons already full can have fully charged tentacles and unleash an impressive electrical charge, enough to make eating them very painful. Swampgrasps, after the initial ambush, tend to strike the floatapus multiple times to get it to discharge in a defensive maneuver before dragging it back into the water, where it's electrical abilities are much more potent - strong enough to be potentially lethal to an adolescent and extremely painful to an adult.

That got out a little more information - I'm unexpectedly busy tonight so will do the full support/locomotion writeup much later tonight/tomorrow, as well as responding to posts, but felt the urge to get this information out so Sabrwolf could get to work on the artwork.a       
Check out my settings, either Urban Jungles or Terra Cephalapodia!

Also, I apologize in advance to sometimes responding to quoted posts separately, my iPad makes it nearly impossible to multi-quote multiple posts.
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