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The largest dinosaurs were long-necked sauropods, especially titanosaurs. There is no definitive, scientifically agreed top ten: estimates of body mass and length use different methods, and some giant species are known only from a few bones. This is an approximate list of major contenders, not a precise ranking. The estimates below are attributed to their sources so you can compare both size and how well each animal is known.
How to compare the biggest dinosaurs
“Biggest” can mean heaviest or longest, and those are not interchangeable. Mass estimates depend on how researchers reconstruct a body from fossil bones; length estimates may include substantial stretches of neck and tail. A spectacular number from fragmentary remains is also less secure than an estimate based on more substantial fossils.
The Natural History Museum’s figures below are its published estimates, not a common-method ranking. Other institutions and studies sometimes report different values. For example, the Field Museum describes its Patagotitan exhibit as about 70 tons and displays a 122-foot cast, while the Natural History Museum gives 57 tonnes and 37.5 metres. A cast is a reconstruction, not a direct measurement of a complete fossil skeleton.
10 of the largest dinosaur contenders
1. Patagotitan
The Natural History Museum estimates Patagotitan at 57 tonnes and 37.5 metres long, and says it may be the longest dinosaur. A 2014 study in Scientific Reports estimated 59.3 metric tonnes for the described individual using limb-bone circumferences. These are method-specific estimates, not a single settled measurement. Patagotitan is among the better-known giant contenders, but the Field Museum’s exhibit figures show that institutions do not all present the same size.
2. Argentinosaurus
The Natural History Museum estimates Argentinosaurus at 70 tonnes and 35 metres long. A 2023 paper abstract in Lethaia gives a mass estimate of 75–80 tonnes. Argentinosaurus is known from fragmentary fossils, so its enormous estimated mass is not as straightforward to establish as a measurement from a complete skeleton.
3. Bruhathkayosaurus
The same 2023 Lethaia abstract provisionally estimates Bruhathkayosaurus at 110–130 tonnes. That would make it a remarkable contender, but the estimate concerns fragmentary remains and is explicitly provisional. It should not be treated as a confirmed record or as directly comparable to better-supported estimates.
4. Puertasaurus
The Natural History Museum estimates Puertasaurus at 50 tonnes and 30 metres. Its known fossil record consists of just four vertebrae, according to the museum, so a full-body size estimate necessarily extrapolates from very limited material. It is a contender, not a securely measured place in a league table.
5. Dreadnoughtus
The Natural History Museum lists Dreadnoughtus at 26 metres long. Its initial mass estimate was above 59 tonnes, but later body-volume calculations brought the figure down to around 22 tonnes; other estimates fall between. A 2023 Lethaia abstract reports 33 tonnes. The spread illustrates how much the method can affect a giant dinosaur’s estimated mass.
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The Natural History Museum gives Sauroposeidon a length range of 27–34 metres and a mass range of 40–60 tonnes. The museum cautions that those estimates may be unreliable because comparisons with Giraffatitan may not account accurately for their relationship. Treat the figures as a broad estimate rather than a precise size.
7. Turiasaurus
The Natural History Museum estimates Turiasaurus at 51 tonnes and 30–39 metres long, and identifies it as the largest dinosaur found in Europe so far. Its length estimate spans a wide range, so it is more useful to understand it as a large European sauropod than as a precisely ranked global record-holder.
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8. Austroposeidon magnificus
A 2016 description in PLOS ONE describes Austroposeidon magnificus from Brazil and gives an estimated length of around 25 metres. The described fossil material is a partial vertebral column; the study does not establish a mass estimate that would support a precise global ranking.
9. Giant Neuquén titanosaur specimen
A 2021 report in Cretaceous Research describes a giant Neuquén titanosaur specimen as one of the largest sauropods found and says it probably exceeds Patagotitan. The report information available here does not provide enough detail for a precise mass or length comparison, so it is best treated as a reported contender rather than assigned a numerical size.
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10. Mamenchisaurus sinocanadorum
The Natural History Museum mentions a possible 15-metre neck for Mamenchisaurus sinocanadorum when discussing Sauroposeidon. That striking neck-length comparison does not establish a whole-body length or mass ranking. It belongs in the conversation about extreme dinosaur proportions, but the available figure alone cannot support a claim that it ranks among the ten heaviest.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What was the biggest dinosaur?
There is no definitive answer that fits every meaning of “biggest.” Patagotitan and Argentinosaurus are leading contenders: the Natural History Museum gives Patagotitan the greater length estimate, while it estimates Argentinosaurus as heavier. Other studies report different values, and Bruhathkayosaurus has a much higher but provisional estimate based on fragmentary remains. The safest answer is that several sauropods may qualify, depending on whether the comparison is about length, mass, or the strength of the fossil evidence.
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