Extinct Species and Groups that Would Have Destroyed the World or Effect the Environment

DinoLover4242

The Top Ten

1 Troodon Troodon

They would have outcompete out native (wild, not domestic) canines of most species if they were brought back from extinction. - DinoLover4242

2 Spinosaurus Spinosaurus

They would have negatively impact native modern crocodilians by preying on them and outcompete native crocodilians to extinction, unless the crocodilians became smaller (to reduce the chance of Spinosaurus finding crocodilians) and/or by becoming fully terrestrial to reduce competition from invasive Spinosaurus. - DinoLover4242

3 Velociraptor Mongoliensis Velociraptor Mongoliensis

They would most likely outcompete most species of canines and possibly big cats (lions, etc) by preying on the same prey items. - DinoLover4242

4 Oviraptor Oviraptor

They would have eaten eggs (if this is true) of native egg-laying reptiles and birds of modern times. They would also outcompete native ground birds and some omnivorous mammals. - DinoLover4242

5 Chalicotherium Chalicotherium

They would have outcompete some native hoofed mammals of modern times to extinction. However, they could replace extinct ground sloths (if ground sloths weren't brought back). - DinoLover4242

6 Therizinosaurids Therizinosaurids

Therizinosaurids, if brought back from extinction, would have no natural predators (other than humans) when they're rhino-sized and would damage the native modern trees by overconsuming them due to the Therizinosaurid's population explosion (much like what happened with many other invasive species that were brought to nonnative areas). - DinoLover4242

7 Deinocheirus Deinocheirus

Just like with Therizinosaurids, Deinocheirus, the giant (possibly herbivorous) Ornithomimid, would devastate native modern trees and some other modern plants by overconsuming them, due to the Deinocheirus population growth caused by lack of Deinocheirus's natural predators (Tarbosaurus, etc). - DinoLover4242

8 Sea Scorpion (Eurypterid) Sea Scorpion (Eurypterid)

These relatives of modern terrestrial scorpions would have devastated some marine life by eating them and would also overpopulate, just like what happened with invasive king crabs in European seas. - DinoLover4242

9 Terror Birds Terror Birds

These carnivorous flightless birds, related to native modern seriemas, would outcompete some native mammal predators by preying on the same prey items and would kill livestock. - DinoLover4242

10 Argentavis Argentavis

These birds would outcompete many native vultures and condors (including the critically endangered California condor) to extinction due to eating the same source of food, dead animals. - DinoLover4242

But it looks like it wouldn’t harm a fly ☹️☹️ - CherryBooks

But it is a type of vulture (or relative) and could compete for food against our native modern vultures and condors. - DinoLover4242

The Contenders

11 Livyatan Livyatan

This giant whale would have devastated large whale populations as they are highly predatory and would kill off blue whales to extinction. They would also be a threat to humans and boats if they mistaken boats for whales and see humans as prey items. - DinoLover4242

Aw I can’t believe it could kill of blue whales until they are extinct. - CherryBooks

You know that blue whales are endangered due to human activities. So if this predatory whale got brought back from extinction and brought to today's oceans, since these whales were way bigger than orcas (yet not as big as sperm whales), this would make matter worse for blue whales. - DinoLover4242

12 Megalodon Megalodon The megalodon is an extinct species of shark which was about 59 feet (18 meters) long and hunted in the seas until about 1.5 million years ago. It was similar to today's great white shark-but three times longer and 20 times heavier. ...read more.
13 Apatosaurus Apatosaurus

There were several dinosaur species closely related to the well known Apotosaurus. They’re not predators or well protected, but if too many were corralled into one small area (ex southern Florida), all of the plants would either be eaten or crushed. The entire ecosystem would collapse.

14 Arthropleura Arthropleura

These giant millipedes would have flourished in modern Earth, if they were genetically engineered to adapt to modern oxygen levels and climate, they would devastate farmed crops like cabbages, lettuce, etc. - DinoLover4242

15 Stegosaurus Stegosaurus

Stegosaurus, if brought back from extinction, would have no natural predators when fully grown (or even almost fully grown). They would also devastate fruit crops, native shrubs and other forms of food meant for modern browsers. They would almost certainly flourish in today's world. - DinoLover4242

16 Protoceratops Protoceratops Protoceratops is a genus of sheep-sized herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period of what is now Mongolia.

This animal, if brought back from extinction, would outcompete many browsing animals native to modern times. They were about as common as today's sheep in their native range, but in modern times, due to lack of its natural predators (Tarbosaurus, etc), they would flourish and their population would explode into that twice the size of their populations of the Late Cretaceous, therefore overconsuming our native plants. - DinoLover4242

17 Psittacosaurus Psittacosaurus Psittacosaurus is a genus of extinct ceratopsian dinosaur from the Early Cretaceous of what is now Asia, existing between 123.2 and 100 million years ago.

Just like Protoceratops, Psittacosaurus, if brought back from extinction, would outcompete many browsing animals native to modern times. They were probably about as common as today's deer in their native range, but in modern times, due to lack of its natural predators (large carnivorous theropods, etc), they would flourish and their population would explode into that twice or more the size of their populations of the Early Cretaceous, therefore overconsuming our native plants. - DinoLover4242

18 Triceratops Triceratops Triceratops is a genus of herbivorous ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the late Cretaceous period, about 68 million years ago in what is now North America.

Triceratops, if brought back from extinction, would outcompete many browsing animals native to modern times. They were the most common non-avian dinosaur in their native range and time, but in modern times, due to lack of its natural predators (large carnivorous theropods, etc), they would flourish and their population would explode into that twice or more the size of their populations of the Late Cretaceous, therefore overconsuming our native plants. - DinoLover4242

19 Ankylosaurus Ankylosaurus Ankylosaurus is a genus of armored dinosaur. Fossils of Ankylosaurus have been found in geological formations dating to the very end of the Cretaceous Period, between about 68–66 million years ago, in western North America, making it among the last of the non-avian dinosaurs.

Ankylosaurus, if brought back from extinction, would outcompete many browsing animals native to modern times. They were uncommon non-avian dinosaur in their native range and time, but in modern times, due to lack of its natural predators (large carnivorous theropods, etc), they would flourish and their population would explode into that twice or more the size of their populations of the Late Cretaceous, therefore overconsuming our native plants. - DinoLover4242

20 Hadrosaurs Hadrosaurs

Many different species of Hadrosaurs, if brought back from extinction, would outcompete many browsing animals native to modern times. They were the most common non-avian dinosaurs in their native range and time, but in modern times, due to lack of its natural predators (large carnivorous theropods, etc), they would flourish and their population would explode into that twice or more the size of their populations of the Late Cretaceous, therefore overconsuming our native plants. - DinoLover4242

21 Iguanodonts Iguanodonts

Many different species of Hadrosaurs, if brought back from extinction, would outcompete many browsing animals native to modern times. They were the most successful non-avian dinosaurs in their native range and time, living in almost every single continent, but in modern times, due to lack of its natural predators (large carnivorous theropods, etc), they would flourish and their population would explode into that twice or more the size of their populations of the Early and Late Cretaceous, therefore overconsuming our native plants. - DinoLover4242

22 Brachiosaurus Brachiosaurus Brachiosaurus is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about 154–153 million years ago.

Just like Apatosaurus, Brachiosaurus would have no natural predators in modern times (if Brachiosaurus was brought back from extinction), they would overconsume our native modern day plants. - DinoLover4242

23 Lystrosaurus Lystrosaurus

These large herbivores, not reptiles nor dinosaurs, but early relatives of mammals, if brought back from extinction, would outcompete some native modern browsers and would overconsume our native plants, seeing how common they were in the Early Triassic (when they were the dominant herbivores and the most successful large animals of that time), their populations would explode in a similar way in modern times, devastating native plants. - DinoLover4242

24 Edaphosaurus Edaphosaurus

Just like Lystrosaurus, Edaphosaurus was neither a reptile nor dinosaur, but a mammal relative, despite its appearance. If Edaphosaurus was brought back from extinction, they would probably outcompete some mammal (for example, some Australian herbivorous marsupials) and reptile herbivores (for example, tortoises) of modern times, and would devastate our native modern plants while also having Edaphosaurus population to explode and thriving. - DinoLover4242

25 Placerias Placerias
26 Cynognathus Cynognathus
27 Thrinaxodon Thrinaxodon
28 Gorgonops Gorgonops
29 Dimetrodon Dimetrodon
30 Dryosaurus Dryosaurus
31 Hypsilophodon Hypsilophodon
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