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= Camarasauridae = Camarasauridae (Greek, from Camarasaurus – chambered lizard) is a family of Neosauropod dinosaurs within the clade Macronaria, the sister group to Titanosauriformes. Among sauropods, camarasaurids are small to medium-sized, with relatively short necks. They are visually identifiable by a short skull with large nares, and broad, spatulate teeth filling a thick jaw. Based on cervical vertebrae and cervical rib biomechanics, camarasaurids most likely moved their necks in a vertical, rather than horizontal, sweeping motion, in contrast to most diplodocids. Cladistically, they are defined to be all sauropods more closely related to Camarasaurus supremus than to Saltasaurus loricatus. More recent revisions, however, have seen the expansion of this definition to include Haplocanthosaurus on the basis of morphological characters.

Characters
Several skeletal features have been used to characterize the camarasaurids. In the skull, these include an external narial diameter approximately 40% of the long-axis length of the skull, an arched internarial bar, a short muzzle anterior to the nares, and maxillary shelf. In the rest of the axial skeleton, these include flat ventral faces on the cervical vertebrae, a triangular flare to the neural spines of the middle and posterior dorsal vertebrae, and a concave posterior surface to the anterior thoracic ribs, as well as an external haemal canal across the anterior vertebrae of the tail. A reduction to two carpals, long metacarpals relative to the radius, and a twisted ischial shaft serve to identify the appendicular skeleton.

Biogeography
Broadly speaking, camarasaurids occupied a distribution limited to the Laurasian continent during the Upper Jurassic. Most currently accepted camarasaurid specimens have been discovered in the Morrison Formation of North America, however some specimens from the African Tendaguru Formation have been speculated to belong to the Camarasaurus genus, and the closely related Lourinhasaurus was found in Portugal. Camarasaurus is one of the better characterized sauropod genera, consisting of four species of which several specimens have been collected: C. supremus, C. grandis, C. lentus, and C. lewisi.

C. supremus was first described by Cope in 1877 as Amphicoelias latus. The current name has been established since Osborn and Mook coined it in 1921. Among camarasaurids, C. supremus was fairly large, with some defining vertebral characters. Specimens have been found in the Morrison formation, specifically southern Colorado and northwestern Oklahoma, in strata dating from the Kimmeridgian to Tithonian stage of the upper Jurassic.

C. grandis was first described by Marsh in 1877 as a species of Apatosaurus. Gilmore (1925) referred it to Camarasaurus. It is distinguished by a particularly tall neural arch in its middle dorsal vertebrae. C. grandis has been found in New Mexico, southern Wyoming, and Colorado, and has been dated to the late Kimmeridgian stage of the Jurassic[8].

C. lentus was described by Marsh in 1889 as Morosaurus lentus. It has been found in Wyoming and across Utah in late Kimmeridgian, Jurassic strata. C. lentus is defined by expansion in the neural spines from caudal vertebrae 1 to 6 and a short, but substantial, neural arch in the dorsal vertebrae.

C. lewisi was first described as Cathetosaurus lewisi by Jensen et al (1988), but was officially resolved to Camarasaurus by McIntosh in 1996. The single specimen was found in Western Colorado in the upper Morrison formation. It is characterized by bifurcated vertebral spines across the length of the vertebral column from the cervical vertebrae to the dorsal. It has been dated to the late Kimmeridgian-Tithonian of the Jurassic.

Speculative Members
Since the initialization of the group with Marsh’s Morosauridae, there has been extensive remodeling in terms of which genera are included. Below is a list of speculative camarasaurids that (A) have been moved outside of the clade, (B) present inadequate material for definitive characterization, or (C) present camarasaurid-like characters but have been classified otherwise.

Aragosaurus: Discovered in 1987, Aragosaurus represented the first new dinosaur genus found in Spain. It was initially placed in Camarasauridae based on vertebral characters indicating status as a basal macronarian, but when McIntosh’s 1990 iteration of the clade fell out of favor as a polyphyly, it could only be established that Aragosaurus was a titanosauriform, but not a titanosaur.

Lourinhasaurus: Found in Portugal’s Lourinha formation, Lourinhasaurus shares a handful of characters with camarasaurids. Given the well-characterized similarities between the Morrison formation in the United States and the Lourinha formation in Portugal, this finding may have presented particular interest to the field. However, a more rigorous classification by Dantas et al. (1998) concluded that Lourinhasaurus merited its own taxon outside of Camarasauridae.

Apatosaurus alenquerensis: A synonym of Lourinhasaurus.

Apatosaurus minimus: Described as an Apatosaur by Mook (1917), this specimen has since been reclassified as a basal camarasauromorph (Macronarian) after some consideration that it expressed camarasaurid character. Whether or not to place it within Camarasauridae directly has not been rigorously investigated.

Cathetosaurus: Upon its discovery in the Colorado Morrison formation, Jensen et al (1988) considered the specimen a new genus. McIntosh (1991) speculated shortly thereafter that the find demonstrated sufficient similarity to Camarasaurus to abandon the new genus in favor of the already-established one.

Tienshanosaurus

Euhelopus

Opisthocoeilicaudia

Chondrosteosaurus