I M Chait has scheduled another of its remarkable natural history auctions with all the artistry and wonder than man never had a hand in up for grabs, led this time by two fantastic fossils.

Firstly, there is a very rare fossil oviraptor skeleton. Oviraptors were first discovered in 1923 by legendary paleontologist and explorer Roy Chapman Andrews.

The discoveries were startling  as some had strange crests, weirdly recurved beaks and other features so strikingly different from other carnivorous dinosaurs that they were amongst the most unique theropod dinosaurs ever found.

New finds in the 1990s showed that most Oviraptors were even covered with feathers, and that they sat over their eggs like modern birds, such that a time traveller going back 70 million years to the Late Cretaceous era would probably have not even realised these were dinosaurs.

Modern debate still rages regarding their lifestyle and biology; studies of the skull and the unusually powerful beak have resulted in dietary suggestions ranging wildly from mammals to lizards and even molluscs such as clams.

Don't let it escape you... the fossil oviraptor dinosaur

Despite the increased number of fossils that have facilitated this research, their fragile, hollow bones remain scarce, most usually found crushed and incomplete.

This, therefore, is a first-class specimen, a complete skeleton superbly prepared, with well-formed skull, thin, fragile rib bones, characteristic bird-shaped hips and long slender legs with wicked-looking curving talons to the feet.

It boasts a lovely clear patination and bone texture throughout, and is evocatively mounted in a running pose on a discreet metal armature, 30 1/4 inches high and 55 inches long overall and estimated at $80,000-100,000.

A rather more recent monster of prehistory was the La Brea Saber-Toothed Tiger, which is represented by an extraordinary example of its skull here.

The Saber-Toothed Tiger, Smilodon fatalis, inhabited the Americas during the last Ice Age. In evolutionary specialization, Smilodon is the ultimate feline. Fossils belonging to these great cats are extremely rare, and are never found outside of the New World.

Say cheese.... the vicious grin of the saber-toothed tiger skull

In the world of paleontology, they are considered purely American - In addition to representing an icon of prehistoric life, Smilodon is the official State Fossil of California.

This offering includes a museum display skull originating from the famous tar pits of La Brea, Los Angeles, California.

It boasts a wonderfully rich dark brown patination and contrasting, creamy enamel to the teeth. A portion of bone is missing on the left side of at the front, exposing the extent to which the enormous saber, or canine, tooth extends deep into the skull.

It is listed at $150,000-200,000 in the auction which takes place on December 4 in California.