Scientists have discovered that otters the size of wolves roamed the Earth six million years ago. The creature was about the size of a wolf making it as much as three times larger than current otters. It is believed that the otter weighed an average of 110 pounds, which is more than double what modern-day otters weigh.
Lead researcher Denise Su said, "One of the really unique things about this discovery is that it's a pretty complete cranium".
The fossil discoveries were particularly significant as otters have a poor fossil record.
"The bones were so delicate that we could not physically restore the cranium".
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Moreover, the new findings suggest that S. melilutra belongs to one of the oldest and most primitive otter lineages, one that goes back at least 18 million years, to the European, badger-like animal Paralutra, the researchers said.
Siamogale melilutra had a large, powerful jaw with the enlarged, bunodont (rounded-cusped) teeth typical of many otter lineages. "Instead, we CT-scanned the specimen and virtually reconstructed it in a computer". The only previous examples of the species, which had features similar to otters and badgers, were isolated teeth that were recovered from Thailand. As to why the ancient otters were so large, scientists aren't sure. And unlike large land mammals in the region, whose dispersal northward was blocked by two broad rivers, these semiaquatic otters and their kin were able to spread unhindered; fossils of a similar species from approximately the same era have been unearthed at another site about 1400 kilometers to the northeast.
Researcher, Xiaoming Wang, said "If Siamogale melilutra was not smart enough to figure out tools, perhaps the only option left was to develop more powerful jaws by increasing body size". But analysis of their evolutionary family tree suggested that the presence of bunodont teeth in several otter species is a effect of convergent evolution - different species independently evolving the same trait because they face similar environmental circumstances.
"A lot of times in modern carnivores, the large size is partly due to subduing prey, so their prey is bigger and the carnivores also get bigger", Su explains.