Let's suppose Paleozoic marine creatures (Trilobites, early fish, and many else) has appeared in oceans of 2017. What kind of advantages and disadvantages will they have when they compete with modern marine creatures? By the way, to make things simple, these Paleozoic creatures have perfectly adapted to modern climate and atmosphere. The only difference is how they look like and how they struggle for their lives.

The species I want to know are :

  • Trilobites

  • Hallucigenia

  • Ostracoderms

  • Tetrapodomorpha
  • Early Amphibians

(And although this is not a marine creature but, if possible)

  • Giant Dragonflies
  • $\begingroup$ I think this is a wonderful question and I have no idea, but I advice you to specify two things: Are you asking if there are general advantages/disadvantages or are you asking how individual species would fare? If the last thing is true, please specify which species. By perfectly adapted you mean adapted to everything (nutrition, disease and so on) except for other sea creatures of similar size? The problem with the word perfect of course is: If they are adapted perfectly, they would just dominate any other species $\endgroup$
    – Raditz_35
    Jun 2, 2017 at 11:59
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    $\begingroup$ @Raditz_35: More to the point, they wouldn't be Paleozoic marine creatures $\endgroup$
    – nzaman
    Jun 2, 2017 at 12:07
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    $\begingroup$ giant dragonflies can't exist today. Size of insects is limited by the amount of oxygen in the air. $\endgroup$
    – Fl.pf.
    Jun 2, 2017 at 12:37
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    $\begingroup$ The Paleozoic spanned 400 million years, and conditions and species varied immensely. You're picking creatures from periods that might be more different from each other than they are from now! So if that's what you want, they're going to fare differently. Have you done any research about these creatures? A good place to start would be ucmp.berkeley.edu/paleozoic/paleozoic.php $\endgroup$
    – Spencer
    Jun 2, 2017 at 12:50
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    $\begingroup$ Ostracoderms seem closely related to horseshoe crabs in terms of functional biology. Apparently so are trilobites (dang that was a long wikipedia entry). Tetrapodmorpha is a very broad clade that would include animals with biology spanning the adorable Axolotl google.com/… and modern fish. So I'm not sure much would differ... $\endgroup$ Jun 2, 2017 at 19:28

2 Answers 2


Honestly, not a lot would happen in the general scheme of things. But, to answer more specifically, we have to consider a couple factors.

How did they get there? Was this the result of humans reviving them a la Jurassic Park? If so, they'd have to have been altered significantly just by the act of de-extinction. They retroactively said the same of JP's "dinosaurs" in Jurassic World. This scenario is a whole kettle of fish on its own ...

If it's just some mysterious time slip or other unintelligent phenomenon bringing literal paleozoic creatures from their time and environment and dropping them in our modern oceans, it's going to end tremendously poorly for them.

For one, they'd have no natural immunity to the modern bacterial and viral ecosystems that have mutated severely since their time (much more so than multi-cellular life has in the same amount of time). So, much of it would die from infections their bodies would have no clue how to combat.

(Before editing, I stated that climate differences would be a huge problem, but I've had it pointed out that I missed you stating they were adapted to our climate so I take this back)

Finally, ecosystems tend to compartmentalize by niches. Creatures in a given environment succeed because chance and passing on of traits has specialized them to fill one or a series of niches in the environment. While these creatures certainly filled such niches in their time, they are filled now by other creatures, most of which are far more suited to the changes in the environment I discussed above.

So the ultimate answer is going to be this: I still stand by my conviction that most of them would die off very quickly, even without climate being a problem. Though I reduce this to 78% or so, versus the 99 I originally stated. Though one comment was right that larger animals may find it easier to bludgeon their way into already-occupied niches, though I worry about competition there still giving an edge to established modern life.

I want to add, the giant dragonfly really -can't- be adapted to our modern environment, because insects simply cannot be that big with the oxygen content of our atmosphere. That's the primary governing factor in why things like that are gone.

  • $\begingroup$ OP specifically said these animals are perfectly adapted to our atmosphere and climate. The bacteria might be a problem though. And as to your comment on niches, there are many instances of foreign animals coming into a different ecosystem and completely dominating. I imagine a large marine animal could easily find a niche in a modern ecosystem. $\endgroup$ Jun 2, 2017 at 20:21
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    $\begingroup$ I missed the part about them being adapted to our atmosphere and climate. In which case I take back a large chunk of what I said. I apologize then. This is what happens when I have to use my spare reading glasses whilst awaiting a new pair. No that's not a joke. $\endgroup$
    – Cereza
    Jun 2, 2017 at 20:28
  • $\begingroup$ The way that giant dragonflies would perfectly adapt to current atmosphere and climate conditions would be to become as small as modern ones. $\endgroup$
    – Sarriesfan
    Jun 2, 2017 at 21:53
  • $\begingroup$ @Starriesfan Yeah, that's a solution. But would there be a lot of difference from any given dragonfly at that point? Sure, there'd be sufficient differences to intrigue an entomologist but, the OP is clearly looking to make these creatures interesting to a broader circle of intellectual readers. Just saying. I think I should stop commenting on this question, I'm making myself sound, unintentionally and unnecessarily like a smarmy jerk. I apologize. $\endgroup$
    – Cereza
    Jun 2, 2017 at 21:59
  • $\begingroup$ @Cereza that was entirely my point, they would not be any different than modern dragonflies, it's the only way they could adapt to live in modern conditions. Which was of course what you had said in your answer. $\endgroup$
    – Sarriesfan
    Jun 3, 2017 at 6:00

They'll struggle to cope with threats which never existed in their time. For instance:

Trilobites were extinct before aerial predators which hunted at sea (pterosaurs, birds) evolved. So they won't have any instincts or survival strategy against a seabird diving into the water to grab them.

For land-based creatures - The whole of Earth's food chain re-wrote itself in the Permian, when vertebrates learned to eat plants. Invertebrates cracked the problem a bit earlier. So the Palaeozoic creatures may not slot into our ecology very well - they'll be trying to find food sources which don't exist or exist in far less quantity).

Modern food chains are short and have links like this: Plant --> herbivore --> carnivore. So that might be grass to zebra to lion, or seeds to ant to small bird to bird of prey.

Pre-Permian food chains were much, much longer and had links like this: Plant --> rotting plant --> small invertebrate (detritivore) --> predatory invertebrate --> small amphibian --> enormous amphibian. Once invertebrates learned to eat plants directly, the rotting plant step becomes optional. Land plants are really tough to digest!

Because there are so many links in this food chain (there may be more invertebrate steps than I bothered to list above) and there is energy loss at each step, the population of the large amphibians thus never gets to the numbers that lions or wolves can build up. So your top carnivores may have a social system or breeding system which relies on huge territories to get enough food. They'll be spread thinly and very rare, which means they are prone to becoming extinct just through bad luck (a drought, a disease outbreak), as well as to having to compete with their modern equivalents - crocodiles, otters, fish eagles and the like.


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