Thanks to advanced methods, it is possible to revive ancient Pokémon from their fossils. However, the reasons why some have gone extinct are sometimes bizarre. MeinMMO ranks the 15 fossil Pokémon for whom evolution did not go well.
What are fossil Pokémon? Fossil Pokémon are prehistoric pocket monsters that are actually extinct. You can think of them somewhat like the dinosaurs from reality. The only difference is that the characters in Pokémon have managed to revive them from their fossils through special methods.
Currently, 25 fossil Pokémon are known. From the entries in the Pokédex, we learn about the terrible fate that has befallen them. MeinMMO lists the 10 saddest reasons why these pocket monsters went extinct.
Perhaps the Pokémon would have benefited from a break like in Pokémon Concierge:
10 Reasons Why Fossil Pokémon No Longer Live
Rank 10: Too Slow (Movement Speed)

Many of the fossil Pokémon that went extinct had to die because they were simply too slow. As a result, they presumably could not catch enough prey and eventually starved. This applies to several Pokémon:
- The spiral Pokémon Amoroso (Gen 1) was hindered in its hunting due to its heavy shell.
- Lecryodon (Gen 8) was revived from two fossils but seemed too sluggish to survive before its revival.
- The prehistoric toad Pokémon Karippas (Gen 5) does not clearly state why it ultimately went extinct. However, the Pokédex entry reveals that it searched for prey on land, even though it was much slower outside of water.
Whether it was their own body that hindered the Pokémon in hunting or their strategy, either way, these prehistoric Pokémon struggle today to find food in the wild. Luckily, there are trainers who can supply the pocket monsters with food.
Rank 9: Too Slow (Evolution)

Kabutops (Gen 1) was like the Pokémon in rank 10, too slow to survive. However, it can’t really be blamed for that: Kabutops originally lived in the water, but over time it developed features to live on land. This is especially noticeable in the gills and legs that changed.
However, Kabutops went extinct before it could fully make the transition to a land dweller. This creature is thus a victim of too slow evolution and presumably could no longer catch prey because it was a hybrid of land and sea creatures.
More causes of death can be found on page 2.