Camarasaurus grandis

In 1877 during the Yale Peabody Museum's expedition to Como Bluff, William Harlow Reed and several other field workers for Othniel Charles Marsh collected a basioccipital and partial postcranial skeleton. Camarasaurus grandis was named by Marsh in 1877 on the specimen (YPM 1901). He initially considered it a species of Apatosaurus.^[11] The next year, Marsh named another new species, Morosaurus impar,^[12] and shortly thereafter reclassified Apatosaurus grandis as Morosaurus grandis and named a third species, Morosaurus robustus.^[13] The type specimens of M. impar and M. robustus could be from the same individual as YPM 1901. Additional material of C. lentus would be collected between 1877 and 1879 by YPM crews, including some skull material. In 1896, Marsh named another species of Sauropod from Como Bluff, Pleurocoelus montanus, based on a fragmentary postcranial skeleton of a juvenile from. The species was later synonymized with C. grandis. All of the material found at Como Bluff came from the Kimmeridgian of the Morrison Formation.

During the Second Dinosaur Rush in 1900, crews of the Field Museum of Natural History collected several appendicular and axial elements, including a nearly complete forelimb, near Fruita, Colorado. The C. grandis material from Fruita led to new reconstructions of Sauropod manus and pes structure. In 1898, Samuel Wendell Williston regarded M. impar as synonymous with M. grandis.^[14] In 1901, Elmer Riggs recognized that Morosaurus was a junior synonym of Camarasaurus.^[4] C. robustus was suggested to be synonymous with C. grandis in 1930 by Richard S. Lull.^[15] In 1958, Theodore E. White synonymized C. grandis with C. supremus.^[16] This proposed synonymy has not been upheld by subsequent study.

A specimen of Camarasaurus grandis was excavated in New Mexico in 1978, and was one of the first partial skeletons from the Morrison Formation to be excavated in the state.^[17] It was initially reported as a specimen of C. cf. supremus in 1982, but reinterpreted as C. grandis in 2005.^[1]

A relatively complete skeleton of Camarasaurus grandis, GMNH-PV 101, was described in 1996.^[18] However, an unpublished study by Emanuel Tschopp and colleagues presented at the 2014 meeting of the Society of Vertebrate Paleontology suggested that this specimen may have closer affinities to Camarasaurus lewisi, which they argued represented a distinct genus, Cathetosaurus.^[19]

Camarasaurus grandis lived during the Kimmeridgian age of the Jurassic in what is now Wyoming, Colorado, and New Mexico.^[1] It is one of the more common species of Camarasaurus, with 9.1% of known Camarasaurus specimens identified as C. grandis (the majority of specimens cannot be identified as belonging to any particular species).^[20]

A specimen of C. grandis^[1] from New Mexico showed signs of having been fed on by Allosaurus.^[17]

Camarasaurus grandis is the geologically oldest species of Camarasaurus, and may be ancestral to the later species of the genus.^[6]