Sauropoda
Sauropods were herbivorous (plant-eating), usually quite long-necked[13] quadrupeds (four-legged), often with spatulate (spatula-shaped: broad at the tip, narrow at the neck) teeth.They had tiny heads, massive bodies, and most had long tails. Their hind legs were thick, straight, and powerful, ending in club-like feet with five toes, though only the inner three (or in some cases four) bore claws.
Their forelimbs were rather more slender and ended in pillar-like hands built for supporting weight; only the thumb bore a claw.
Many illustrations of sauropods in the flesh miss these facts, inaccurately depicting sauropods with hooves capping the claw-less digits of the feet, or multiple claws or hooves on the hands. The proximal caudal vertebrae are extremely diagnostic for sauropods.[14]
Size
Size comparison of selected giant sauropod dinosaurs
The sauropods’ most defining characteristic was their size. Even the dwarf sauropods (perhaps 5 to 6 metres, or 20 feet long) were counted among the largest animals in their ecosystem. Their only real competitors in terms of size are the rorquals, such as the blue whale. But, unlike whales, sauropods were primarily terrestrial animals.
Their body structure did not vary as much as other dinosaurs, perhaps due to size constraints, but they displayed ample variety.
Some, like the diplodocids, possessed tremendously long tails, which they may have been able to crack like a whip as a signal or to deter or injure predators,[15] or to make sonic booms.[16]
Supersaurus, at 33 to 34 metres (108 to 112 ft) long,[17] was the longest sauropod known from reasonably complete remains, but others, like the old record holder, Diplodocus, were also extremely long.
The holotype (and now lost) vertebra of Amphicoelias fragillimus may have come from an animal 58 metres (190 ft) long;[18] its vertebral column would have been substantially longer than that of the blue whale.
However, a research published in 2015 speculated that the size estimates of A. fragillimus may have been highly exaggerated.[19]
The longest dinosaur known from reasonable fossils material is probably Argentinosaurus huinculensis with length estimates of 25 metres (82 ft) to 39.7 metres (130 ft).[20][21]
The longest terrestrial animal alive today, the reticulated python, only reaches lengths of 6.95 metres (22.8 ft).[22]
Others, like the brachiosaurids, were extremely tall, with high shoulders and extremely long necks.
Sauroposeidon was probably the tallest, reaching about 18 metres (60 ft) high, with the previous record for longest neck being held by Mamenchisaurus.
By comparison, the giraffe, the tallest of all living land animals, is only 4.8 to 5.5 metres (16 to 18 ft) tall.
The best evidence indicates that the most massive were Argentinosaurus (120 metric tons[23]), Puertasaurus (80 to 100 metric tons [24]), Alamosaurus, Paralititan, Antarctosaurus (69 metric tons[23]).
There was poor (and now missing) evidence that so-called Bruhathkayosaurus, might have weighed over 175 metric tons but this has been questioned.[25]
The weight of Amphicoelias fragillimus was estimated at 122.4 metric tons[18] but 2015 research argued that these estimates may have been highly exaggerated.[19]
The largest land animal alive today, the Savannah elephant, weighs no more than 10.4 metric tons (11.5 short tons).[26]
Among the smallest sauropods were the primitive Ohmdenosaurus (4 m, or 13 ft long), the dwarf titanosaur Magyarosaurus (6 m or 20 ft long), and the dwarf brachiosaurid Europasaurus, which was 6.2 meters long as a fully-grown adult.[27]
Its small stature was probably the result of insular dwarfism occurring in a population of sauropods isolated on an island of the late Jurassic in what is now the Langenberg area of northern Germany.[28][29]
The diplodocoid sauropod Brachytrachelopan was the shortest member of its group because of its unusually short neck.
Unlike other sauropods, whose necks could grow to up to four times the length of their backs, the neck of Brachytrachelopan was shorter than its backbone.
On or shortly before 29 March 2017 a sauropod footprint about 5.6 feet (1.7 meters) long was found at Walmadany in the Kimberley Region of Western Australia.[30] The report said that it was the biggest known yet.