Sauropods of the Late Triassic and Early Jurassic

Fossil evidence for the earliest sauropods is often incomplete and fragmentary. Listed here are some of the best known taxa. Their geographic range was widespread, like that of the "prosauropods." Evidence for basal sauropods has been found on the continents of Africa, Asia, Europe, and possibly North America, South America, and Australia.

Antetonitrus (Late Triassic, South Africa). One of the earliest known sauropods is Antetonitrus, from Late Triassic rocks dating from 220 million to 215 million years ago. It lived in what is now South Africa, an area also known for an abundance of "prosauro-pods." Measuring between 26 and 33 feet (8 and 10 m) long, Ante-tonitrus typified a transitional form between a "prosauropod" and a sauropod. It retained some of the features found in "prosauropods," such as a grasping claw on its front feet and legs and feet that had not yet been optimized like the weight-bearing limbs of later sauropods. Yet the size and bulk of Antetonitrus testify to its lifestyle as a quadruped and make it the first known member of the sauropods. The dinosaur is known from a single specimen, probably that of a juvenile, consisting primarily of limb, foot, and vertebral elements. The skull is not yet known. Antetonitrus was identified and named by British paleontologist Adam Yates and South African paleontologist James Kitching. Its name means "before the thunder," a poetic tribute to a precursor of the Earth-shaking giants to follow.

Blikanasaurus (Late Triassic, Lesotho). This South African mini-giant had the bulk and quadrupedal posture of a sauropod packed into a small frame that measured about 20 feet (6 m) long. Dated to about 216 million years ago, it was slightly younger than Anteto-nitrus. Blikanasaurus was named after Blikana Mountain in South Africa and is known from only a few bones of the left hind limb, including the tibia, fibula, and foot bones. These limb elements originally were believed to be part of a heavily built "prosauropod," but paleontologists Paul Upchurch and Peter Galton used cladistic analysis to determine that the limb elements of Blikanasaurus more closely matched those of sauropods.

Gongxianosaurus (Early Jurassic, China). This enigmatic and tantalizing specimen was found in China and first described in 1998 by the Chinese paleontology team of Xinlu He, Changsheng Wang, Shangzhong Lui, Fengyun Zhou, Tuqiang Lui, Kaiji Cai and Bing Dai. The only specimen of Gongxianosaurus ("Gongxian lizard") lacks most of the skull but has a fairly complete postcranial skeleton. This early sauropod dates from the Early Jurassic Epoch. The animal was about 47 feet (14 m) long. Its forelimbs were long, and its femur was straight and longer than the tibia, a trait of the sturdy-limbed sauropods. The skull is known only from its premaxilla and some teeth. Gongxianosaurus is one of the most complete specimens of an early sauropod.

Kotasaurus (Early Jurassic, India). The Indian sauropod Kotasau-rus ("Kota lizard") is known from the combined disarticulated— unconnected—vertebrae and leg bones of up to 12 individual specimens collected since 1988, when the creature was first named by Indian paleontologist P. Yadagiri on the basis on a single pelvic bone. The largest known individual of Kotasaurus was about 30 feet (9 m) long. Only two teeth have been found. They are leaf-shaped, with smooth edges, and they are more like the teeth of later sau-ropods than the teeth of "prosauropods." Other affinities with the sauropods include Kotasaurus's great size, its four sacral vertebrae, its pelvic girdle, and its straight femur. Kotasaurus also retained some basal sauropodomorph features, including a bump on the upper side of the femur and a node on the ankle bone that is not found in more derived sauropods.

Vulcanodon (Early Jurassic, Zimbabwe). First described in 1972 by Rhodesian paleontologist Michael Raath, Vulcanodon ("volcano tooth") was the earliest known sauropod until recent discoveries from the Late Triassic, including Antetonitrus and Blikanasaurus. Its name refers to the fossil bed where the original specimen was found, which was sandwiched between two lava beds. The animal is known from a partial skeleton and a scapula found separately. At 22 feet (6.5 m) long, Vulcanodon was of moderate length. It had spatu-late, "prosauropod"-like teeth but otherwise resembled a sauropod in skeletal structure with its quadrupedal posture, four fused sacral vertebrae, and polelike femur. Vulcanodon is of interest to scientists because even though it lived during the Early Jurassic Epoch, it still retained many primitive features also seen in older "prosauropods," such as the shape of its pelvic girdle and the digits of its feet.

Tazoudasaurus (Early Jurassic, Morocco). Tazoudasaurus ("Ta-zouda lizard") was recently named by an international team of paleontologists led by Rollan Allain of France. Found in Morocco, the specimen consists of a partially articulated skeleton with skull material. Tazoudasaurus was related to the line of sauropods that produced Vulcanodon and that formed the foundation of the Middle Jurassic radiation of sauropods known as the Eusauropoda. The jaw of Tazoudasaurus had several primitive features. These included a high tooth count in its lower jaw (20 leaf-shaped teeth in the lower jaw); V-shaped, rather than U-shaped, tooth rows; and teeth that did not rub together when the jaw was closed. Tazoudasaurus was about 30 feet (9 m) long.

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