Sauropodomorphs Sauropodomorph size is difficult to estimate given their usually fragmentary state of preservation. Sauropods are often preserved without their tails, so the margin of error in overall length estimates is high. Mass is calculated using the cube of the length, so for species in which the length is particularly uncertain, the weight is even more so. Estimates that are particularly uncertain (due to very fragmentary or lost material) are preceded by a question mark. Each number represents the highest estimate of a given research paper. One large sauropod,
Maraapunisaurus fragillimus, was based on particularly scant remains that have been lost since their description by paleontologists in 1878. Analysis of the illustrations included in the original report suggested that
M. fragillimus may have been the largest land animal of all time, possibly weighing and measuring between long. One later analysis of the surviving evidence, and the biological plausibility of such a large land animal, suggested that the enormous size of this animal was an over-estimate due partly to typographical errors in the original report. This would later be challenged by a different study, which argued Cope's measurements were genuine and that there was no basis for assuming typographical errors. The study, however, also reclassified the species and correspondingly gave a much lower length estimate of and a mass of . This in itself would later be disputed as being too small for an animal of such size, with some believing it to be even larger at around and weighing around . Another large but even more controversial sauropod is
Bruhathkayosaurus, which had a calculated weight ranging between and a length of Although the existence of this sauropod had long been dismissed as a potential fake or a misidentification of a petrified tree trunk, recent photographic evidence emerged, confirming its existence. More recent and reliable estimates in 2023 have rescaled
Bruhathkayosaurus to weigh around with its most liberal estimate being , making it incredibly massive for such an animal. If the upper unlikely size estimates were to be taken at face value,
Bruhathkayosaurus would not only be the largest dinosaur to have ever lived, but also the largest animal to have lived, exceeding even the largest
blue whale recorded. According to
Gregory S. Paul, 'super-sauropods' or 'land-whales' such as
Maraapunisaurus,
Bruhathkayosaurus and the "Broome Titanosaur footprints," as he calls them, should not be surprising as sauropods were more heat tolerant and grew rapidly, which allowed them to reach truly titanic sizes that rivalled the largest whales in mass despite the prevalence of air sacs. Moreover, in a 2024 publication, Gregory S. Paul further argued that a sauropod's internal air sacs were not as dramatically density reducing as has been widely thought, suggesting that masses reaching close to 200 tons was within the realm of possibility. '', often considered the largest-known dinosaur The
sauropods were the longest and heaviest dinosaurs. For much of the dinosaur era, the smallest sauropods were larger than almost anything else in their habitat, and the largest were an
order of magnitude more massive than anything else known to have walked the Earth since. Giant prehistoric
mammals such as
Paraceratherium and
Palaeoloxodon (the largest land mammals ever discovered) were dwarfed by the giant sauropods, and only modern whales approach or surpass them in weight, though they live in the oceans. There are several proposed advantages for the large size of sauropods, including protection from predation, reduction of energy use, and longevity, but it may be that the most important advantage was dietary. Large animals are more efficient at digestion than small animals, because food spends more time in their digestive systems. This also permits them to subsist on food with lower nutritive value than smaller animals. Sauropod remains are mostly found in
rock formations interpreted as dry or seasonally dry, and the ability to eat large quantities of low-nutrient browse would have been advantageous in such environments. One of the tallest and heaviest dinosaurs known from good skeletons is
Giraffatitan brancai (previously classified as a species of
Brachiosaurus). Its remains were discovered in
Tanzania between 1907 and 1912. Bones from several similar-sized individuals were incorporated into the skeleton now mounted and on display at the
Museum für Naturkunde Berlin; this mount is tall and long, and would have belonged to an animal that weighed between . One of the longest complete dinosaurs is the
Diplodocus, which was discovered in
Wyoming in the United States and displayed in
Pittsburgh's Carnegie Natural History Museum in 1907. There were larger dinosaurs, but knowledge of them is based entirely on a small number of fragmentary fossils. Most of the largest
herbivorous specimens on record were discovered in the 1970s or later, and include the massive
titanosaur Argentinosaurus huinculensis, which is the largest dinosaur known from uncontroversial and relatively substantial evidence, estimated to have been and long. Some of the longest sauropods were those with exceptionally long, whip-like tails, such as the
Diplodocus hallorum In 2014, the fossilized remains of a previously unknown species of sauropod were discovered in Argentina. The titanosaur, named
Patagotitan mayorum, was estimated to have been around long weighing around , larger than any other previously found sauropod. The specimens found were remarkably complete, significantly more so than previous titanosaurs. It has since been suggested that
Patagotitan was not necessarily larger than
Argentinosaurus and
Puertasaurus. In 2019,
Patagotitan was estimated to have been long and about . The largest of non-sauropod
sauropodomorphs was the unnamed long unnamed Elliot giant.
Yunnanosaurus youngi also reached a length of .
Theropods Tyrannosaurus was for many decades the largest and best-known theropod to the general public. Since its discovery, however, a number of other, comparably-sized giant carnivorous dinosaurs have been described, including
Spinosaurus,
Carcharodontosaurus, and
Giganotosaurus. These large theropod dinosaurs are estimated exceed
Tyrannosaurus in length, though more recent studies and reconstructions show that
Tyrannosaurus, although shorter, was more heavily built and thus still comparable to them in mass and overall size. The largest known
Tyrannosaurus specimens such as
Sue and
Scotty are currently
estimated to be the most massive individual theropod specimens known to science, though by only a narrow margin; a considerable bias in sample size resulting from the much greater number of adult specimens in
Tyrannosaurus compared to all other theropods of similar mass, combined with the majority of individual adult giant theropods (even with
Tyrannosaurus) never having entered the fossil record, mean it is difficult to judge which, if any, of these theropods was the largest by mass in reality. There is still no clear explanation for exactly why giant theropods grew to be so massive compared to any land predators that came before and after them. The largest extant theropod (avian dinosaur) is the
common ostrich, up to tall and weighs between . The smallest non-
avialan theropod known from adult specimens may be
Anchiornis huxleyi, at in weight and in length, although later studies discovered a larger specimen reaching . However, some studies suggest that
Anchiornis was actually an avialan. The smallest dinosaur known from adult specimens which is definitely not an avialan is
Parvicursor remotus, at and measuring long. However, in 2022 its
holotype was recognized as a juvenile individual. Among living avian dinosaurs, the
bee hummingbird (
Mellisuga helenae) is smallest at and long. The smallest theropod overall (including avians) is the currently extant bee hummingbird at 6.12 cm long and 2.6g for females, and 5.51 cm long and 3.25g for the males. '', the smallest potentially non-avialan dinosaur. In
the theropod lineage leading to birds, body size shrank continuously over a period of 50 million years, from an average of down to . This was the only dinosaur lineage to get continuously smaller over such an extended time period, and their skeletons developed adaptations at about four times the average rate for dinosaurs.
Ornithischians . The largest of ornithischians is the
hadrosaur Shantungosaurus from the province of
Shandong,
China, measuring at least 15 meters (49 feet) in length and weighed at least 13 tonnes (14 short tonnes).
Magnapaulia, another hadrosaur from Mexico, has the most recent estimate placing the animal's size at 12.5 meters (approximately 41 feet) long and weighed 9.77 tonnes (10.77 short tons). Other large ornithischians include: •
Triceratops: a large ceratopsian, and the most famous of its kind, measuring somewhere between 8-9 meters (26-30 feet) and weighing 6-10 tonnes (6.6-11 short tons). Animals of similar size include
Torosaurus,
Eotriceratops, and the controversial
Titanoceratops. •
Ankylosaurus: a large ankylosaur, one of the most armoured animals ever, and possibly the largest of all
ankylosaurids, with a length of 8 meters (26 feet), and a weight of 7.95 tonnes (8.76 short tons). Other
ankylosaurs barely reach any longer than 6 meters (20 feet) in length. •
Dacentrurus and
Stegosaurus: The most recent estimates for
Dacentrurus make the animal 8-9 meters in length and 5-7.4 tonnes (5.5-8.2 short tons). However, a specimen of
Stegosaurus, nicknamed
Apex, is the most complete of any
Stegosaurus skeletons, and measured 8.2 meters in length. •
Pachycephalosaurus: the largest definitive member of
Pachycephalosauria. Measured 4.5 meters (14.8 feet) and weighed 370-450 kg (820-990 lbs). Another ornithischian of similar size is
Manidens, another heterodontosaurid. ==See also==