3.6" Fossil Sauropod Rib Section w/ Metal Stand - Colorado

This is a 3.6" wide fossil sauropod dinosaur (Camarasaurus grandis?) rib bone section, collected from the Late Jurassic-aged Morrison Formation in Colorado. The bone is very dense from silicification (gembone). It is accompanied by the pictured metal display stand.

Agatized or agate replaced dinosaur bone is a rare form of fossilized dinosaur bone where the original fossilized bone, typically permineralized with calcite, has been re-mineralized with silica-type compounds such as agate, jasper, chalcedony, or opal.

In a unique and isolated circumstance, the strata on the Colorado Plateau were uplifted during the tertiary intrusions about 35 million years ago when the San Rafael Swell and the La Sals, Henry, and Abajo Mountains were formed. As these ranges were forming, local strata layers were flooded with silica-rich, superheated groundwater. This provided the appropriate environment to start this calcite-silicate replacement in the original fossils. The most prolific layers of gem bone come from the Morrison Formation, which is late Jurassic in age.

Camarasaurus was a medium-sized sauropod dinosaur whose fossils are found in the Morrison Formation of the Southest United States. It is estimated to have reached lengths of up to 75 feet long and had an estimated maximum weight of around 50 tons. Compared to contemporary Diplodocids, it had a shorter tail, longer forelimbs, and a much larger and more robust skull.

An artists rendering of Camarasaurus.  By Jesus Gamarra.  Creative Commons License
An artists rendering of Camarasaurus. By Jesus Gamarra. Creative Commons License

Camarasaurus skulls are quite distinctive: they have blunt snout and quite a square shape. Camarasaurus had large, spoon-shaped teeth, unlike many sauropod dinosaurs that had small, peg-like teeth. This likely indicates that it ate coarser vegetation, allowing it to share the same environment as other sauropods without competing for food. It may have replaced its teeth approximately every 60 days as they became worn from chewing. Its cervical vertebrae had hollow chambers to reduce weight on the neck, leading to its name, which means “chambered lizard”.

A Camarasaurus skull cast showing the spoon-shaped teeth.
A Camarasaurus skull cast showing the spoon-shaped teeth.

Camarasaurus is considered the most abundant of the sauropod dinosaurs found in North America. Its fossils have been found in almost every major Morrison Formation dinosaur locality, with fossils found in localities from across many states including New Mexico, Utah, Colorado, Montana and Oklahoma.

Located in the midwestern United States, the Late Jurassic-aged Morrison Formation is an incredibly large and fossiliferous formation that dates back to about 156 to 147 million years old. Named after the small town of Morrison, Colorado, the formation was discovered in 1877, and quickly became the center of one of the biggest rivalries in historical paleontology.

19th century paleontologists Othniel Charles Marsh and Edward Drinker Cope spent 15 years making outstanding strides in the discovery of fossils all throughout the American Midwest, but also resorted to unsavory methods in attempts to discredit or ruin the other's work and reputation, including destruction of specimens.

The total area of the formation is roughly 600,000 square miles, but much of that is inaccessible, deeply buried under prairie land and eroded during the formation of the Rocky Mountains. Even so, many outcroppings across the Front Range and upper Midwest allow paleontologists access to a wealth of information from Late Jurassic North America.

Dinosaurs from the region include large allosaurid dinosaurs, such as the eponymous Allosaurus and its larger relative Saurophaganax. Both exceeded 30 feet in length, making them some of the largest carnivores of their time. They competed with the similarly large megalosaurid Torvosaurus, and the somewhat smaller horned ceratosaurid, Ceratosaurus. On the smaller end of the theropod family tree was the raptor-like Ornitholestes.

For herbivores, Stegosaurus guarded their herds with huge, intimidating backplates and formidable tail spikes. Small, early ankylosaurs like Gargoyleosaurus would have fed on the forested understory, smaller in size than the 30+ foot giant Stegosaurids.

However, the Morrison Formation's main attraction were the giant sauropod dinosaurs, some of the most colossal of dinosaurs and largest land animals of all time. Diplodocus, Camarasaurus, Apatosaurus, Brontosaurus, Brachiosaurus, Barosaurus, and Supersaurus all count themselves among these long-necked titans. None of these herbivores would have been less than 50 feet in length at adult size: the largest of their number would have exceeded 100-115 feet in length, and over 40 tons. For so many sauropods to have lived in roughly the same place and time, they all likely developed different feeding and living strategies to minimize competition. Their massive sizes and herds would have defended them well from any of the numerous predators of the Morrison.
Camarasaurus grandis?
Skull Creek, Dinosaur, Colorado
Morrison Formation
Bone: 3.6 x 2.25"
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