The Biogeography of the Komodo Dragon...
Evolution:
They share a common past with dinosaurs but are not direct descendants. Both dinosaurs and monitor lizards belong to the subclass Diapsida (Ciofi, 1999). The earliest fossils from this subclass go back to the late Carboniferous period, about 300 million years ago. Monitor lizards are related to Lepidsauria which emerged from Diapsida, about 250 million years ago at the end of the Paleozoic era. About 100 million years ago, during the Cretaceous era, a species related to contemporary varanids appear in the fossil records of central Asia. Marine lizards from this species went extinct, along with dinosaurs, about 65 million years ago. During the Eocene, 50 million years ago, land monitors spread throughout Europe and South Asia. The Varanus genus appeared and evolved about 40 and 25 million years ago in Asia. Varanids made it to Australia about 15 million years ago when Australia collided with southeast Asia. Then 2 million years later a second lineage differentiated and moved throughout Australia and the Indonesian archipelago when the two were much closer. Lower sea levels allowed the dragons to reach their destination. Varanus komodoensis differentiated from its earliest Australian relative about 4 million years ago (Ciofi, 1999). Komodos migrated to the islands of Flores, Rinca and Gila Motang, which were joined about 10,000 years ago. The island of Komodo joined the other islands around 20,000 years ago during the last Ice Age.
Fossil evidence supports the idea that Komodo dragons may be relics of a larger distribution, stretching as far as the eastern portion of Flores to Timor. Fossils from pygmy elephants, stegodont, found on both Timor and Flores suggest that the two islands may have been close enough to allow migration during the Pleistocene era. The existence of large mammals provided an adequate supply of food to feed lizards as large as Komodo dragons and possibly larger. Megalania prisca, a varanid, could have reached lengths up to 23 feet and weighed up to a ton due to the existence of stegodonts or pygmy elephants (Diamond, 1992). These enormous varanids, that have been extinct for 25,000 years, may explain how Komodo dragons evolved to be such large carnivores in an ecosystem that has a limited amount of resources...