I've been making a story about an lost world island, roughly the size of Madagascar, (593.40 km²). I have currently estimated that I could have herbivorous animals up to 3 tons in weight (sauropods) , and carnivores up to 1 ton (tyrannosaurs) , but I am not sure. Thus im looking for someone to help me out with this problem and hopefully give me the max weight estimation on land animal on the island.

  • $\begingroup$ Hi DeadlyCow welcome.. but I think it will be difficult. Madagascar may suffice, but on a smaller island, it will be implausible. You'd need a lot of food. Large volumes, a tropical rain forest.. else, a food chain cannot be maintained. Your big herbivores need a lot of plant life to support them ! The larger a predator, the larger its territory needs to be. As a consequence, in evolution, the opposite seems to happen.. animals get smaller on islands.. Read this en.wikipedia.org/wiki/Insular_dwarfism $\endgroup$
    – Goodies
    Commented Nov 27, 2021 at 12:52
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    $\begingroup$ Just a note: Madagascar has an area of 587,000 km² (227,000 sq. mi.). That is more than two and a half times the area of Great Britain, or 90% of the area of France, or about 85% of the area of Texas. It is a large island. $\endgroup$
    – AlexP
    Commented Nov 27, 2021 at 17:25

2 Answers 2


The Island Rule states that on islands large animals become smaller and smaller animals become larger. So elephants on an island would become smaller and rodents would become larger.


The prehistoric breakup of the supercontinent Gondwana separated the Madagascar–Antarctica–India landmass from the Africa–South America landmass around 135 million years ago. Madagascar later split from India about 88 million years ago during the late Cretaceous period allowing plants and animals on the island to evolve in relative isolation.[26]


So dinosaurs living on Madagascar any time during the last 20 million years of the Cretaceous Era should have been the right size to flourish on an island of that size.


Large sauropod dinosaurs known only from Madagascar after it separated from Indian and became an island include:




Carnivorous dinosaurs from the late Cretaceous in Madagascar include:



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