A pair of duelling sabre-toothed cats carry an estimate of $200,000-250,000 ahead of an auction at IM Chait in Beverly Hills on July 26.
The Dinictis Feline skeletons were discovered separately in the badlands of South Dakota in 1998 and 1999 and are extremely well preserved - 50-60% and 70-80% complete, respectively.
Jake Chait, director of IM Chait's natural history department, commented: "No comparable display specimens of the same quality and originality exist in either private or museum collections."
Dinictis, a member of the Nimravinae family widespread across the northern states of the US, first appears in the fossil record 37.2m years ago and died out around 16.8m years later.
In 2011, the skull of a Machairodus Giganteus, the largest in the sabre-toothed family, made $116,500 at Bonhams New York.
A pterosaur skeleton is another lot likely to inspire fierce bidding on the day of the auction. The lot was found in the phosphate beds of Morocco and is valued at $110,000-140,000.
The animal was the first vertebrate ever to take to the skies and lived between 228m and 66m years ago.
It's thought that without the oxygen rich atmosphere of the late cretaceous period (100m-66m years ago) they would have been unable to fly, a factor that may have contributed to their extinction.
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