A fossilised plesiosaur skeleton achieved £90,000 ($119,223) at Summers Place on November 21.
The prehistoric predator was discovered in Lyme Regis in Dorset – incidentally where young Mary Anning found the first plesiosaur in 1823.
This plesiosaur is around 205m years old
At around 90% complete, it’s one of the finest specimens extant.
It was originally valued at £30,000 ($39,741), a figure it trebled.
Summers Place spokesman Rupert van der Werff told the BBC: "It is very rare to find a plesiosaur preserved in 3D, most that come up for sale are on fossilised plates.
"This is the best of its kind that I have seen...
"Plesiosaurs are pretty rare, even on the Jurassic Coast - you are a hundred times more likely to find an ichthyosaur than a plesiosaur."
A Siberian mammoth tusk from the Pleistocene era (2.5m-11,700 years ago) achieved £33,750 ($44,701).
The lot measures close to three metres in length and weighs 54kg.
It likely originates from a particularly large bull mammoth.
An auroch skeleton was another highlight, pulling in £30,000 ($39,741).
The auroch was a bull that roamed Europe, Asia and north Africa for a period of close to two million years.
The last known survivor was killed by hunters in the Jaktorow Forest in Poland in 1627. Fewer than 24 complete skeletons are known to exist.
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