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This question is all about how a shark can evolve to have the following traits:

  • Amphibious
  • Pack behavior
  • Dromaeosaurid form (bipedal, scaly, with four talons and a sleek but strong frame-resembling a movie Velociraptor)
  • Capable of climbing trees and rocks and so forth
  • Sharp claws resembling shark fins, may be notched

Why I'm Asking: Currently, Velocisharks have evolved into Scosharks, which are anthropomorphic and exhibit human intelligence and can make and use tools, but this is through the influence of a highly powerful mage's essence, so this is beyond the bounds of the question.

However, I needed to ask this question, as my idea of Scosharks includes the above traits and Reaville (where they live) is a low-fantasy setting, plus I like to include or account for science in my stories, so I need to know how Velocisharks could develop to have the above traits so they can become Scosharks.

I appreciate your input, thank you!

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    $\begingroup$ Hate to break it to you but shark is less prone to evolution... But no worry leave it to the professional, us and our generous gifts to the ocean we can speed things up with everyone on board. Kudos to Japan discharging tons of nuclear waste water ;D $\endgroup$
    – user6760
    Nov 25 at 6:30
  • $\begingroup$ The answer is going to have to be “magic”. $\endgroup$ Nov 25 at 7:10
  • $\begingroup$ Received wisdom says you and I evolved from sea creatures but that's clearly not to say we should still be named as they were… If what you describe was possible, how would it still be in any every-day sense related to a shark? That said, why would it be useful to describe every step of the critter's evolution in the world you're building? If you want a shark to evolve into a velocishark - even to keep some visible features that justify the same name - why not write the story that way? In your world, why must "they evolved from sharks" not be reasonable? $\endgroup$ Nov 25 at 21:50
  • $\begingroup$ @RobbieGoodwin: the idea is that by understanding how they would have developed, I can better understand where they'd live and how they'd behave. Make sense? $\endgroup$
    – Alendyias
    Nov 26 at 3:36
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without some very special circumstances, it's hard to make it work.

See, while many creatures have changed quite a bit over time to adapt to new environments (see cetaceans and pinnipeds for example), Sharks, Crocodilians and Dragonflies, in general terms, are essentially the trinity of "I reached this body plan a couple hundred million years ago and decided it was close enough from perfect". These creatures are just so well adapted to where they live and what they do that they barely had to change anything over the millenia, and why a large number of them still look so much like many of their extinct counterparts.

but let's try anyway.

The big problems here to even begin the "transformation" are:

0- finding a good shark candidate and getting them isolated

1- making them unable to continue as they are

2- forcing them down the amphibian-esque evolutionary path

3- finish applying all pressures that led to dromeosaurids

Step 0 is there because of 2 reasons: a shark that can't breathe while still will probably have a much harder time in a transition to an environment with much less water and room to swim in. Furthermore, as they'll be twisted in every way they'll need to be isolated from most sources of competition, lest they'll be kicked out of the evolutionary race by already adapted species.

With that difficulty established, I'm fairly confident that our best bet for a velocishark ancestor is...the epaullete shark.

enter image description here

Quoting from the link:

The environments that epaulette sharks inhabit are complex, shallow, obstacle-filled coral reef systems. In order to successfully navigate the cracks and crevices of this habitat while pursuing their prey (crustaceans, worms, and small fish), epaulette sharks evolved the ability to walk along the seafloor using an undulating, crawling motion. This movement is possible through evolutionary adaptations in their pectoral and pelvic fins that have increased their range of motion and functionality as “feet.” Even though they can swim just fine, these sharks are often seen ably walking along the seafloor or across the reef.

The second adaptation that allows the epaulette shark to walk on land is its ability to survive for extended periods of time with little to no oxygen. The reef systems that these incredible “walking” sharks inhabit can be very shallow—so shallow that during low tide isolated pools of water form between exposed reef structures. Those pools can trap fish, crabs, and other animals, and the level of oxygen in the water can drop by 80% or more through their respiration. Epaulette sharks can become trapped in those low oxygen pools, and they are also known to actually walk across exposed sections of the reef to hunt for prey in places where other predators can’t go and prey have little chance of escape. To be able to survive with little or no oxygen in those situations—as they pursue isolated prey, or escape from low-oxygen tide pools—epaulette sharks have evolved the ability slow their heart rate and breathing, and to gradually limit blood flow to certain parts of the brain.

Together, the epaulette shark’s ability to a) walk on its pectoral fins, and b) survive for extended periods with little or no oxygen allow these incredible sharks to actually walk on land.

Wrapping up: this shark is likely the best candidate because it is already adapted to function in regions of shallow water with low oxygen availability and has basic adaptations to move on land, and make them a pretty great candidate for an amphibious creature that descends directly from a shark. Some tweaks to make this thing able to breathe air and we're ready to start our land-shark evolutionary path.

And there's where the trickiest part is. Even this shark, despite its extensive adaptations to an environment with poor oxygen availability in the water where it can and does often have to walk around on land, all of its adaptations are centered around making do with the oxygen available in the water, while many species of fish in similar or even more drastic situations have adapted to rely on actual lungs or even on their swimming bladders instead to be able to survive. Therefore we likely need to go for one of 2 options:

1- using magic to turn their gills into lungs.

2-trying to rip off ghost crabs and coconut crabs and hope for the best.

1 needs no explanation so I'll go straight to 2: ghost crabs spend extensive periods of time outside of water, yet they make use of gills. How? They keep them moist. Our land shark would likely need to go through similar adaptations to a nurse shark, as right now the ability to breathe while standing still by actively pumping water through the gills will be useful.

From there, we'd need these sharks to slowly adapt to be less dependent on water. Their gills would need to change in order to keep them from collapsing out of water, the shark would also need to be able to pump air through those gills with their mouth, in a system not unlike frog breathing. This would take a long time to happen and would require changes such as a watery environment with oxygen levels getting lower over time with no way for the shark population to leave to more hospitable waters.

With a good amount of luck and the right pressures and mutations, it should be possible to get a species of semi-amphibious shark, capable of still using its gills on land and being much less dependent on water, needing to return to moisturize their gills.

enter image description here

As for the other adaptation for life on land, From the eppulete shark skeleton above, It would still take some specific mutations, but the skeletal structure on their fins should have enough to allow for the evolution of limbs. The "final" result of this stage could vary. Depending on whether the shark started to rely on its skin to breathe in addition to its gills, you could end up with something that looks like a smooth or a scaly salamander.

The next step would be to finish adapting their lungs to life on land. Adult coconut crabs, despite being crabs, will drown if they stay too long underwater. The reason for that is because these crustaceans evolved structures known as Branchiostegal lungs, which, as far as I'm aware, are essentially what you get when you convert the gills of a crab into lungs. Because of this adaptation, coconut crabs are much less reliant on water, and do not need to engage in activities like moisturizing gills in order to breathe (it's also worth noting that these seem to be efficient at the diffusion of gases, as the coconut crab is the largest land arthropod in the world). Your land shark would need to have their gills going through a similar process, ideally converting into something very similar to actual lungs. In a case of success, your land shark would become much less dependent on water to breathe, and could begin its development into the shark equivalent of reptiles. From them on, assuming the gill lungs are at least as efficient as regular lungs, all you should need to do is play the evolutionary pressures that led to Dakotaraptor (except that they might not evolve feathers depending on some things such as how their scales are, whether they keep it and what happens to the kept scales as they evolve), and then add in pressures that lead them into adopting a more lifestyle. Boom velocishark done

Some of these steps most likely require a lot of luck, have a low probability of playing out exactly as needed and it's borderline impossible to be certain that it could happen or if it could happen as predicted. But still, it's likely not impossible, from the evidence of crustaceans seemingly making pseudo-lungs out of gills and adapting to a life on land to the adaptations of this shark to the evolution of tetrapods from fish, it shouldn't be impossible to pull off. If everything goes wrong, we add in just enough magic to give the process the push it needs to happen.

Remember though: your biggest enemies for this to work without extreme reliance of magic would be probability itself and competition with other already established creatures. There's a reason you don't often see many different creatures occupying the same niche in the same place at the same time, usually natural selection acts in order to have only one come out on top.

May the odds be in your shark's favor.

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I think it is highly unlikely.

Sharks are already highly specialized creatures, and specialization comes at the expenses of flexibility and versatility.

I cannot see how a shark can modify its body plan in a way that doesn't negatively impact its fitness to the environment.

Let's take just one feature: going on land.

To do this, it should start frequenting tidal pods and environments where lack of water is regular. Sharks need to move in water to keep breathing, and their hunting habits depend on having water into which they can move and attack. Basically frequenting tidal pods is a U turn for shark evolution, as it would require many synchronized changes to keep it fit to the environment.

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  • $\begingroup$ Sharks appear to have reached the optimal adaption to the environment since they haven't evolved for a very long time. Therefore I totally agree with your point, sharks wouldn't change, especially not as drastically as described. $\endgroup$
    – RancidCrab
    Nov 25 at 8:50
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Becoming Amphibious

To become amphibious, they will need at least some way to breathe on land, which is an issue. Cartilaginous fish, such as sharks, diverged from the rest of the jawed vertebrates before the evolution of lungs, and they overall are quite poor at processing air. The only source for a lung would be the spiracles. These could be used for breathing air to supplement a low oxygen environment. Once this function is established, they will evolve to increase the efficiency of these spiracle-lungs, which would entail them growing and expanding into the chest and becoming more intricate and convoluted like mammalian or reptilian lungs. They would also need some way of pumping air into and out of these lungs. These lungs would be attached both to the external spiracles and to the mouth

They will also need a ribcage. As sharks already have ribs, it isn't much of a stretch for these ribs to form a proper ribcage to protect their organs from some predator

Once they have lungs and a ribcage, they should be fully able to live on land

Pack Behaviour

This is easy to justify. If there are enough animals that only a pack can take down, which provide more meat per pack member than smaller animals caught hunting alone, then pack behaviour will quickly evolve

Dinosaur Form

This form could be an adaptation for cursoriality. Using only 2 legs is more efficient in terms of running, and a streamlined, aerodynamic body is also good for avoiding drag. And your shark, with their long, thick tails, should be pretty able to evolve for bipedality

Climbing

Climbing animals often have adaptations that are opposed to cursorial animals. However, if you don't need the sharks to climb all that well, then it should be possible: they'd just need some sort of rough scales/teeth on the back of their claws that would provide grip as they climbed

Shark-Fin Claws

Such a claw design would have to be more blade-like. However, there seem to be no real obstacles to this structure, due to the fact that sharks do not have any sort of digit structure localized to the end of the fin

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I think highly unlikely. Consider the evolution of teeth in sharks. Shark teeth are designed to catch fast moving prey (and to tear quickly in the process), specific to fish moving in water. Thus, the skull shape, and corresponding jaw containing teeth are unlikely to resemble a predator that catches its prey exclusively in water.

At the same time there is research done among larger sharks, such as the Megalogon, suggesting that their large size contributed to having smaller teeth relative to other sharks the same size, and smaller in size. So, other physical attributes are important to take into consideration too, specific to the evolution of teeth, (and overall skull).

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