Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as Saltasaurus loricatus, Diplodocus longus, and all animals directly descended from their most recent common ancestor.

Neosauropoda is currently delineated by specific shared, derived characteristics rather than the time period in which its members lived.

[4] As Neosauropoda is a subgroup of Sauropoda, all members also display basic sauropod traits such as large size, long necks, and columnar legs.

A great number of neosauropod skeletons were unearthed in western North America during the late nineteenth and early twentieth centuries, primarily Apatosaurus, Camarasaurus, and Diplodocus.

Around 230 million years ago, animals such as Eoraptor, the most basal known member of Dinosauria and also Saurischia, already displayed certain features of the Sauropod group.

[10] There were several major trends in the evolution of sauropodomorphs, most notably increased size and elongated necks, both of which would reach their culmination in neosauropods.

Basal members of Sauropodomorpha are often collectively termed prosauropods, although this is likely a paraphyletic group, the exact phylogeny of which has not been conclusively determined.

True sauropods appear to have developed in the Upper Triassic, with trackways from a basal member known as the ichnogenus Tetrasauropus being dated to 210 million years ago.

[14] Diplodocid and brachiosaurid members of the group composed the greater portion of neosauropods during the Jurassic, but they began to be replaced by titanosaurs in most regions through the Cretaceous period.

In North America and Asia, much of their role as large herbivores had been supplanted by hadrosaurs and ceratopsians, although they remained in smaller numbers all the way until the Cretaceous-Paleogene extinction.

Certain members of the subgroup Titanosauria have ridges along their posterior teeth, but these are not large enough to be considered denticles of a form similar to those found in more basal sauropods.

Haestasaurus, the first dinosaur known from skin impressions, preserved integument over a portion of the arm around the elbow joint approximately 19.5 by 21.5 cm (7.7 by 8.5 in) in area.

[22] José Bonaparte originally described Neosauropoda as comprising members of four sauropod groups: Dicraeosauridae, Diplodocidae, Camarasauridae, and Brachiosauridae.

[24] From Upchurch 1995:[25] Vulcanodon Barapasaurus Shunosaurus Omeisaurus Mamenchisaurus Euhelopus Cetiosaurus Brachiosaurus Haplocanthosaurus Camarasaurus Opisthocoelicaudia Malawisaurus Alamosaurus Saltasaurus Nemegtosaurus Quaesitosaurus Dicraeosaurus Amargasaurus Apatosaurus Diplodocus Barosaurus lentus In 1998, Sereno and Wilson published a cladistic analysis of the sauropod family which proposed Macronaria as a new taxon containing Camarasaurus, Haplocanthosaurus, and Titanosauriformes.

Conventional cladistics had long considered titanosaurs and diplodocoids to be more closely related, with brachiosaurids and camarasaurids together forming a sister taxon.

From Upchurch et al. 2004:[28] Rebbachisauridae Dicraeosauridae Diplodocidae Brachiosauridae Saltasauridae Macronaria is defined as all neosauropods more closely related to Saltasaurus loricatus than Diplodocus longus.

Macronaria is an exceedingly diverse clade, with members ranging in size from anywhere between six and thirty-five meters in length and sporting a broad array of body shapes.

Some synapomorphies which have been used to characterize macronarians include flared neural spines on the dorsal vertebrae and nearly coplanar ischial distal shafts.

In addition, the most distal vertebrae develop a biconvex shape and together form a long, bony rod at the end of the tail, often referred to as a “whiplash tail.” Increased caudal count and a whiplash tail may be features shared by all members of the Diplodocoid group, but, due to a scarcity of evidence, this has yet to be proven.