A New Migration Route in the Evolution of European Hadrosauroids: The Bulgarian Land Bridge

During the Late Cretaceous, global sea levels were much higher than today. As a result, much of Europe—being relatively low-lying—was fragmented by shallow seas into a vast archipelago composed of numerous islands. Such a landscape fostered unusual ecosystems. Island environments often impose strong ecological constraints, including limited space and restricted resources. Under these conditions, large animals frequently evolve smaller body sizes as an adaptation to island life, a phenomenon known as island dwarfism.

A modern analogy can be seen in the Formosan black bear of Taiwan, which is considerably smaller than the Asian black bears living on the Asian mainland. The opposite pattern may also occur: smaller species living on islands may evolve larger body sizes because competition is reduced and large predators are often absent. This evolutionary trend is known as island gigantism, as illustrated by the dodo, which was much larger than its closest relatives.

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