BOULDER, COLO.- A 24-inch shoulder spike from a Kentrosaurus, a massive Tyrannosaurus rex pelvis and the skulls of two prehistoric saber-toothed predators are among the highlights of an upcoming Artemis Fine Arts auction in Louisville, Colorado.

The sale, titled Fine Fossils, Native American, Asian, Ethno, begins on August 6, 2026, at 9 a.m. GMT-6. The wide-ranging auction brings together fossils, Native American artifacts, Asian art and antiquities, as well as Egyptian, Greek, Roman, Etruscan, Near Eastern, Pre-Columbian and Tribal objects. Fine and visual art will also be represented.



A rare Kentrosaurus shoulder spike

Leading the selection is an exceptionally rare fossilized shoulder spike from a Kentrosaurus that lived in what is now Tanzania during the Late Jurassic period, approximately 152 million years ago. The fossil carries an estimate of $40,000 to $60,000.

Kentrosaurus belonged to the stegosaurian family of plant-eating dinosaurs, whose members are known for the rows of bony plates and spikes that extended along their bodies. Although related to the more familiar Stegosaurus, Kentrosaurus had a particularly dramatic arrangement of defensive projections, including spikes running along its spine and at the shoulders of its forelimbs.

Earlier reconstructions placed these spikes near the animal’s hips, but later discoveries indicated that at least some were positioned at the front shoulders. Scientists have also proposed that the bony core may originally have been covered by an additional horn-like sheath, making the spike even larger and more formidable in life.

The slightly curved fossil measures 24 inches long and has a thick, substantial base. Its surface has developed a rich umber coloration over millions of years. According to the auction house, the specimen has been carefully prepared and is free of surrounding stone and sediment, with restoration limited primarily to the tip.

Mounted on a custom stand, the fossil reaches a height of 10.75 inches. A printed photograph of the Kentrosaurus skeleton at Berlin’s Natural History Museum accompanies the lot as a reference.

The specimen comes from a private Texas collection and was previously handled by Artemis Gallery. It was earlier part of a private collection in Berthoud, Colorado.



A monumental Tyrannosaurus rex pelvis

The next major fossil is a vast Tyrannosaurus rex pelvis from the western United States, dating to the closing years of the Cretaceous period, around 68 million to 66 million years ago. Estimated at $60,000 to $90,000, the fossil is presented on a custom wood and metal display stand.

Measuring 49 inches long and 26 inches wide, the pelvis preserves the broad, outward-flaring ilium and the heavy acetabular area where the powerful hind limbs connected to the body. Its sweeping shape, deep central basin and dense bone structure offer a striking indication of the enormous weight and muscular force carried by the dinosaur’s lower body.

Tyrannosaurus rex remains one of the most recognizable animals in the history of paleontology. As one of the dominant terrestrial predators of the Late Cretaceous, it has remained central to both scientific study and popular culture.

While teeth and smaller fragments from the species periodically appear on the market, large anatomical sections of this scale are far less common. The pelvis is particularly important because it reveals how the animal’s immense body was balanced and supported over its powerful hind legs.

The complete mounted display stands approximately 25 inches high. Because of its size and weight, the auction house notes that the lot will require specialized shipping arrangements.

The fossil comes from the private Hagar collection in Wildwood, Missouri.



A saber-toothed predator with preserved teeth

Another highlight is the fossilized skull of a saber-toothed tiger dating to the Late Miocene, approximately 23 million to 5 million years ago. The skull, which was excavated in Asia, is estimated at $37,500 to $55,000.

The specimen is notable for the preservation of its dentition. The teeth on the right side are complete, while those on the left are nearly complete. Large eye sockets rise on either side of the snout, giving the fossil a powerful and immediately recognizable profile.

Saber-toothed predators have long captured the public imagination, appearing in museum displays, television programs and animated films. Their oversized canine teeth made them some of the most distinctive mammalian hunters of the prehistoric world.

The best-known North American examples are associated with the La Brea Tar Pits in Los Angeles, where fossils from more than 1,000 saber-toothed cats have been recovered. The animal represented in the Artemis sale, however, comes from Asia and offers collectors an example from a different prehistoric population.

The skull measures 11.5 inches wide, 5.875 inches high and 5.5 inches deep. It comes from a private collection in New Jersey and was reportedly excavated during the 1980s.

A rare skull from a “false” saber-toothed cat

Completing the group is a rare fossil skull from Nimravus, a prehistoric predator often described as a false saber-toothed cat. Found in the Sharps Formation of Shannon County, South Dakota, the fossil dates to the Oligocene period, around 31 million to 24 million years ago. It carries an estimate of $30,000 to $45,000.

The skull is displayed with its lower jaw slightly open, exposing the animal’s long canine and saber-like teeth. The pose gives the fossil a vivid sense of animation, suggesting the predator poised to seize its prey.

Although Nimravus looked similar to later saber-toothed cats such as Smilodon, it was not a true member of the cat family. Instead, it belonged to the Nimravidae, an extinct group of carnivorous mammals that independently developed many cat-like characteristics.

Nimravus grew to approximately four feet in length and is thought to have been an ambush predator. Rather than pursuing prey over long distances, it likely relied on concealment and sudden attacks to capture birds and small mammals.

The skull measures nine inches long and five inches wide. Mounted on its custom stand, it reaches a height of 10.25 inches. Its prominent saber tooth measures approximately 1.25 inches long.

Fossils of Nimravus are considerably less familiar to the general public than those of Smilodon, making the specimen an unusual opportunity to acquire a striking example of evolutionary convergence—the process through which unrelated animals develop similar physical adaptations.

Together, the four fossil lots reflect more than 120 million years of prehistoric life, from the armored dinosaurs of the Jurassic to the specialized mammalian predators of the Miocene and Oligocene. Their scale, preservation and visual impact are expected to make them focal points of the August sale.