All sauropods had a generally similar body plan featuring a small head, a long neck, a huge body, quadrupedal posture, and a long tail.
Traits that united the sauropods included sturdy, upright limbs to support their massive weight; four or more fused or sacral vertebrae connecting the spine to the pelvic bones; strong, weight-bearing feet; elongation of the neck; a U-shaped mouth opening optimized for stripping vegetation from stems and tree branches; and pneumatic concavities in their spinal bones that provided lightness without sacrificing strength and may also have housed air sacs that were involved in these animals' breathing. Though possessing these similarities, sauropods also developed significant variation that resulted in the evolution of several distinct groups. These groups were mostly distinguished by anatomical differences of the skulls, vertebrae, and limbs.
Dinosaur Clades and Relationships: Sauropoda
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Sauropods are divided into several subgroups, as shown in the accompanying figure depicting the evolutionary relationships of the Sauropodomorpha.
Of these sauropod groups, only the Neosauropoda definitely had subgroups that survived into the Cretaceous Period. The basal Sauropoda—including the most primitive sauropods, such as Blikanasaurus (Late Triassic, South Africa) and Vulcanodon (Early Jurassic, Zimbabwe)—lived during the Late Triassic and Early Jurassic. The basal Eusauropoda, whose members still retained some primitive characteristics, lived from the Early Jurassic to the Late Jurassic and are known from more than nine genera, including Shunosaurus (Middle Jurassic, China); Barapasaurus (Middle Jurassic, India); Patagosaurus (Middle Jurassic, Argentina); Turiasaurus (Late Jurassic, Spain); and the very-long-necked Omeisaurus (Middle Jurassic, China) and Mamenchisaurus (Late Jurassic, China).
Neosauropoda is the third major group of sauropods; the clade was made up of the largest number of taxa as well as the best known. Many neosauropods date from before the Cretaceous Period, including such iconic dinosaurs as the long and slender diplodocids (Apa-tosaurus and Diplodocus, Late Jurassic, western North America); the tall and bulky brachiosaurs (Brachiosaurus, Late Jurassic, Tanzania, western United States); and the stocky camarasaurs (Camarasaurus, western North America).
Although a few members of the Brachiosauridae and odd relatives of diplodocids have been found in rocks dating from the Early and mid-Cretaceous, the success story of Cretaceous sauropods truly belongs to the Titanosauria, a line of robust, wide-bodied, long-necked plant eaters that became widely distributed, especially in Europe, the Southern Hemisphere, and Asia, and whose last members are found in deposits dating from the Late Cretaceous, at the very end of the time of the dinosaurs. The geographic distribution of these sauropods and their best-known members are described below.
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