The earliest known dugong fossils were found in 50 million-year-old marine sediments. At that point in geologic time, two different groups of sirenians, or so-called sea cows, had already evolved---dugongs being one of them, and manatees being the other. Interestingly, both species are related to elephants.
Found in warm coastal waters, dugongs can grow up to 10 feet long, weigh up to 1,100...
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