Camarasaurus lentus

Lore & Background

The holotype specimen of Camarasaurus lentus was collected from Quarry 13 at Como Bluff, Wyoming, and stored at the Peabody Museum of Natural History under the catalog number YPM 1910. In 1889, Othniel Marsh described it as a new species, which he named Morosaurus lentus. The skeleton was later mounted in the Peabody Museum Hall in the 1930s, and remained mounted until the 2020s. Marsh used the name Morosaurus for many species now assigned to Camarasaurus, which had been named by his rival Edward Drinker Cope; the two genera were recognized as synonymous in the early 20th century.

In 1909, Earl Douglass discovered a rich fossil site in Utah, Carnegie Quarry, which became part of Dinosaur National Monument in 1915. Excavations there yielded much additional C. lentus material, including the nearly complete juvenile specimen CM 11338, described by Charles W. Gilmore in 1925. Another complete articulated adult skeleton (USNM V 13786) was collected in 1918 and later mounted at the National Museum of Natural History. Additional specimens were discovered by the Wyoming Dinosaur Center in 1992, among the most complete adult specimens of the species.

Reader's Guide

Camarasaurus lentus is significant as one of the best-known sauropod species, with exceptionally complete remains that have advanced understanding of sauropod anatomy and ontogeny. The juvenile specimen CM 11338, the most complete sauropod fossil ever discovered, provides rare insight into growth patterns, showing that the neck lengthened with age and that neural spine bifurcation increased. The species is the most abundant among Camarasaurus specimens that can be identified to species, representing 11.1% of such specimens. Its fossils are found in the Morrison Formation, particularly at Dinosaur National Monument, where the 'Wall of Bones' preserves specimens still in rock. The species coexisted with a diverse fauna including Apatosaurus, Diplodocus, Stegosaurus, Allosaurus, and others. Its classification has been debated: Takehito Ikejiri noted that the holotype is a juvenile from strata where C. grandis is more typical, suggesting it may actually belong to C. grandis. C. lentus may be descended from C. grandis and may be ancestral to C. supremus, which first appears shortly before C. lentus disappears.

Did You Know?

• The juvenile specimen CM 11338 is the most complete sauropod fossil ever discovered.
• C. lentus is the most abundant among Camarasaurus specimens that can be identified to species, making up 11.1% of such specimens.
• Two of the fourteen known sauropod specimens with complete necks belong to C. lentus.
• The holotype of C. lentus was originally named Morosaurus lentus by Othniel Marsh in 1889.

Discovery Amid the Bone Wars

Camarasaurus entered science during one of paleontology's most bitter rivalries. In early 1877, David Baldwin, a collector working for Othniel Charles Marsh, stumbled upon enormous bones atop a Colorado peak nicknamed "The Nipple" at Garden Park. Neither Baldwin nor Marsh expressed interest, and the find sat largely overlooked until local teacher Oramel W. Lucas encountered the site on a hunting trip. Lucas wrote to Edward Drinker Cope, who offered payment for excavation. The first shipment Cope received was a theropod jaw, which he named Laelaps trihedrodon. The second package held vertebrae of a far larger animal that Cope called the most bulky land creature known at the time. He published the name Camarasaurus supremus in a rushed 1877 paper, coining a term meaning "chambered lizard" after the hollow spaces in the neck and back bones. Lucas and his brother Ira kept sending material to Cope through 1884, assembling most of a skeleton. Meanwhile, Marsh's rival finds at Como Bluff, Wyoming, produced the genus Morosaurus, whose species were later reassigned to Camarasaurus.

Anatomy and Feeding Ecology

Camarasaurus lentus was a stocky sauropod distinguished by a notably broad rib cage and a skull that, relative to body size, was larger and more robust than those of its relatives. Its jaws generated considerable bite force, supported by 13 to 14 teeth along each side of the upper jaw and 13 along each side of the lower. These teeth had a distinctive spoon-like shape, angled forward, and were replaced rapidly throughout life. Rather than indiscriminately stripping vegetation, C. lentus was likely a selective browser, reaching feeding heights of roughly two to five meters above the ground. The animal's overall build—bulky torso, powerful cranium, and specialized dentition—suggests a creature adapted to processing tougher plant material than many other Morrison Formation sauropods. Skin impressions preserved on a single specimen offer rare direct evidence of its external covering, while multiple individuals bear traces of healed injuries, bite marks, and arthritis, painting a picture of a long-lived animal that endured physical wear and inter-specific encounters over decades.

An Unparalleled Fossil Record

No other dinosaur is as abundantly represented in the Morrison Formation as Camarasaurus, with more than 530 specimens recovered from Late Jurassic rocks across the western United States. This extraordinary sample size makes it one of the best-understood sauropods in the fossil record. The specimens span the full life cycle: from a presumed embryonic individual to an animal estimated to have reached roughly 40 years of age, one of the oldest documented ages for any dinosaur. The species C. lentus, the most commonly encountered, measured approximately 15 meters in length, while C. supremus was substantially larger. Multiple individuals show pathological signs including bite marks and arthritis, and at least one preserves skin impressions. Researchers have also proposed that Camarasaurus populations may have undertaken seasonal movements to escape the dry conditions that periodically affected the Morrison basin. From 1909 onward, several largely complete skeletons were uncovered at Carnegie Quarry in what is now Dinosaur National Monument; some of these, including a nearly intact skull, still rest embedded in the quarry wall.

Taxonomy and the First Sauropod Reconstruction

Four species are commonly accepted within Camarasaurus: C. supremus, C. grandis, C. lentus, and C. lewisi. The genus belongs to the sauropod group Macronaria, and some paleontologists place it alongside Tehuelchesaurus and Lourinhasaurus in a family called Camarasauridae. C. supremus may represent the youngest species, concentrated near the top of the Morrison Formation stratigraphy. The taxonomic history is tangled by the Bone Wars rivalry: Cope named the genus in 1877 from Garden Park material, while Marsh's Como Bluff finds produced Morosaurus, whose species were subsequently reassigned to Camarasaurus. In a landmark moment for paleoart, zoologist John A. Ryder produced a life-sized skeletal reconstruction drawing in 1879 under Cope's supervision. Measuring 68 feet in length, it was the oldest known sauropod reconstruction, though it was not published until 1914 by Charles Craig Mook at a reduced scale. Because little skull material was known at the time, the drawing depicted a carnivorous-looking head with long, sharp teeth—an assumption later overturned.