Dinosaur FAQ: Size and Weight

What were the longest/heaviest dinosaurs?

Question

In the light of all this distortion and uncertainty, what can be said about the largest genera of dinosaurs? What are the heaviest and longest genera that we can speak of with confidence?

Answer

Disclaimer

If we require totally unambiguous evidence for measurements, then the longest dinosaur is still boring old Diplodocus carnegiei, at a relatively modest 27m (89 feet) - because it's the longest dinosaur for which we have a complete skeleton. Nevertheless, we can be confident that other dinosaurs, for which we have more fragmentary remains, were longer. For example, consider Supersaurus:

• It is very clearly closely related to Diplodocus.
• The parts of the specimen that we have are much larger than the corresponding bones in Diplodocus.
• The material, while not complete, is substantial enough for us to have some confidence in the scale factors.

By contrast, when we consider the heaviest dinosaur, data is harder to come by. Different scientists are liable to give wildly differing weight estimates for any given genus (see ``Why do mass estimates vary so much?'' ); and the weight of any species will vary between individuals, and the weight of any individual will vary through its life and seasonally. However, we can still make estimates, and compare what we know of various genera.

Here, then, are the ``biggest dinosaur'' candidates, in something akin to descending order of credibility:

Contenders

1. Argentinosaurus huinculensis

Argentinosaurus is currently the conventional answer to the ``biggest dinosaur'' question. The sacrum, vertebrae and tibia that we have indicate that it is a member of the titanosaur family, and comparison with better-known titanosaur genera give us a good indication of its scale, suggesting a total length of 35m (114 feet) or longer. Given the bulkiness of titanosaurs, its likely weight was in the region of 80-100 tons.

### What particular better-known genera are used for this comparison?

2. Paralititan stromeri

This recently-discovered Egyptian titanosaur was announced in June 2001, and widely described as ``the second biggest ever discovered''. Its humerus, at 1.69m in length, is somewhat smaller than that of Argentinosaurus, at 1.81m, suggesting that if the animals were simialrly proportioned, it was 93% a long as Argentinosaurus, that is, about 32m (104 feet). This would suggest a weight in the region of 65-80 tons.

3. Argyrosaurus superbus

Another titanosaur, estimated at about 28m (92 feet) and 45-55 tons.

4. Sauroposeidon proteles

Closely related to Brachiosaurus, but with a substantially longer neck - about 12m (39 feet) in length, compared with maybe 9m (30 feet) in the better-known genus.

Sauroposeidon is only known from a series of four well-preserved cervical vertebrae, so it's impossible to be certain about the size of the rest of the animal. However, features of those vertebrae suggest that it was particularly specialised towards supporting a long neck, which suggests that the rest of its body may have been proportionally somewhat smaller than in Brachiosaurus. Accordingly length is estimated in the region of perhaps 30m (97 feet) with a mass in the region of 50-60 tons.

Perhaps a more interesting Sauroposeidon statistic is that its long neck and high brachiosaurid shoulders mean that it would have been the tallest known dinosaur, able to raise its head perhaps 18m (58 feet) above ground level.

5. Supersaurus vivianae

This large diplodocid is known from relatively fragmentary remains: one cervical vertebra, several dorsals, a few cordals and a scapulocoracoid. That's enough to tell a pretty impressive story, though.

Consider the sole Supersaurus cervical. Its long, low shape suggests that it can't be from any further back than C9 or C10, yet it's 1.35m long. This compares with a length of .6m for C10 of the Diplodocus carnegiei specimen CM84. We can conclude, then that Supersaurus's neck was 2.25 times as long as Diplodocus's six-meter neck, which suggests a neck of 13.5m (44 feet). Wow. That's longer than Sauroposeidon's neck (but it probably couldn't be raised as high.)

It's tempting to think that the whole animal was 2.25 times as long as Diplodocus, but that won't do: the height of its dorsal vertebrae is ``only'' 1.5 times that of Diplodocus's, suggesting that the neck of Supersaurus was disproportionately long for its body, as in Barosaurus. Nevertheless, it's hard to imagine the animal's total length as much less than 40m (130 feet), with a weight in the region of 40-50 tons.

6. Seismosaurus hallorum

Another large diplodocid from the same period as Supersaurus, but probably rather smaller - opinions differ. David Gillette, its describer, estimated its length at about 45m (150 feet), based in part on on comparison of tail vertebrae to juvenile elements in the Smithsonian's mounted Diplodocus, which is actually a composite. More recent estimates tend to be in the range of 33-37m (110-120 feet).

(It's also recently been argued that hallorum is actually a large species of Diplodocus, in which case Seismosaurus would be a junior synonym.)

7. Aphicoelias fragilimus

###

Amphicoelias fragilimus- 56-62 meters, 125-170 tons

8. Bruhathkayaosaurus matleyi

###

Bruhathkayosaurus matleyi- 44.1 meters, 175-220 tons
http://www.cmnh.org/dinoarch/2001Jun/msg00626.html
http://www.cmnh.org/dinoarch/2001Jun/msg00665.html

9. As-yet unnamed Australian footprints

###

Date: Tue, 30 Oct 2001 12:15:29 +1100
From: "Steve Salisbury" 
To: Dinolist 
Subject: Re: largest dinosaur

> Regarding trackways--somewhere on this list, or maybe elsewhere,
> I've seen reports of huge sauropod tracks from Australia that are
> supposed to be a couple of meters across. This would represent an
> animal in the size range of Amphicoelias fragillimus described
> above. Anyone know any more about these tracks?

The trackways you're talking about were found around 1987 in the
Broome Sandstone, Western Australia.  One set of tracks in particular
belonged to an animal with feet that were 1.5 m long.  The best
estimates for a sauropod with feet this big is 40-50 m, or about the
same size as Amphicoelias fragillimus is thought to have been.

For more details see

Thulborn, T., Hamley, T. & Foulkes, P. 1994. Preliminary report on
sauropod dinosaur tracks in the Broome Sandstone (Lower Cretaceous) of
Western Australia. Gaia 10: 85-94.

Summary

###

Non-Sauropods

### Much much more to say here. Don't forget to mention Shantungosaurus.

What were the longest/heaviest predatory dinosaurs?

Question

Answer

Note that with the exception of the T. rex ``Sue'', most of the specimens that will be discussed here have not yet been properly described or repeatably measured, so we cannot really trust the estimates given for them.

Contenders

1. Giganotosaurus

Described by Coria & Selgado in 1995, this carcharodontosaurine is perhaps 14.5m (47 feet) in length, making it the longest currently known. Weight estimates are in the region of seven to eight tonnes, which would also make it probably the heaviest known predator.

2. Carcharodontosaurus

This African relative of Giganotosaurus has been known for seventy-odd years, but from relatively small specimens. More recent finds have ranged up to 14m (45 feet) in length with weight estimates of up to seven or eight tons.

There's a particularly impressive photograph by Brendan Smith <brendan2076@hotmail.com> showing just how huge this animal's skull is: see dinosauricon.com/images/carcharodontosaurus-bs.html. Now stop and think that Giganotosaurus, a very similar animal, is known to be even larger. Ulp!

3. T. rex

The largest fully-excavated, reasonably complete T. rex is the Chicago Field Museum's specimen nicknamed ``Sue''. Sue is about 12.6m (41 feet) in length, and a fairly typical weight estimate would be six tonnes (although like all dinosaur weight estimates, you can easily find people who will tell you that it's way too high, and others who will tell you it's way too low.)

In the summer of 2000, an expedition headed by Dr. John Horner (author of The Complete T. Rex) found five new T. rexes, at least one of which is claimed to be 10% bigger than Sue, but it's too early to say much about these specimens, which have not even been excavated yet.

Another contender for the ``biggest T. rex'' title is ``Rigby's rex'' - an undescribed specimen currently locked away somewhere in Montana, awaiting attention. It's odd in that Rigby describes the skull as being of ``normal size'', but the pubic bone is very large - 133cm, compared with 122cm for ``Sue'' (and 118cm for Giganotosaurus). This suggests either a new, differently-proportioned Tyrannosaurus species (or a new genus), or more likely, two specimens mixed up together - one normal sized, the other truly huge.

4. Spinosaurus

The only really good Spinosaurus specimen, found by Stromer's team in north Africa in 1911, was destroyed by allied bombing raids during WWII. The remaining evidence suggests that this animal, big as it is, was sub-adult. The implication is that an adult Spinosaurus would have been in the same league as T. rex - probably somewhat longer, but not as heavily built.

A large Spinosaurus skull, rumoured to be eight feet long, has turned up more recently. If the measurement is correct, this would suggest that the complete animal was longer than any known Giganotosaurus or T. rex, but there are no reliable sources yet.

5. Allosaurus

Generally when people mention Allosaurus, they're referring to the common species Allosaurus fragilis; but there's another species, known from much more fragmentary remains: Allosaurus amplexus (previously in its own genus, ``Epanterias'').

Originally described by Cope way back in 1878, it has rather dropped out of sight. However, anecdotally, its claws are at least twice as heavy as those of a thirty-foot A. fragilis. This suggests that it was about 25% bigger than the A. fragilis (1.25³ =~ 2.0), implying a total length of about 11.5m (38 feet).

Allosaurus amplexus is a nomen dubium, at least in the Dinosauricon - see dinosauricon.com/genera/allosaurus.html. Why?

Mickey Mortimor posted a message on the mailing list elucidating some details of large specimens of Allosarus and related genera. It can be found at www.cmnh.org/dinoarch/2001Jan/msg00445.html

6. Acrocanthosaurus

This is another allosaurid, which had tallish spines - perhaps 50cm or so - along its back. Size estimates of known specimens range up to 12m (39 feet), with vague promises of larger specimens to be described.

7. Torvosaurus

This close relative of Megalosaurus, from the very end of the Jurassic period, is known from rather sketchy remains. But is considered likely to have been about 12m (39 feet) in length, and heavily built with it.

8. An As-Yet Unnamed Argentinian Carcharodontosaurine

In Patagonia, Phil Currie and Rodolf Coria have recently discovered a bonebed containing several individuals of a new, as-yet unnamed, carcharodontosaurine. The individuals in the bed vary in age and size, but the largest seem to be bigger than Giganotosaurus. As always, we have to ``wait for the paper'' before we can say anything very definite.

9. ``Das Monster von Minden''

``The Monster of Minden'' is a badly-documented late-Jurassic specimen from the Wiehengebirge, Germany. The German edition of National Geographic for November 1999 contains an article in which this animal's ribs are described as 1.5 times as large as those of Allosaurus (which it resembles), and its teeth are claimed to be a foot long (including the root.) This might imply an overall length of 15m (about 49 feet) but again, more information is needed. The specimen has not yet even been referred to any species or genus.

Summary ... And perhaps even a Conclusion

First of all, we need to bear in mind that we have so few specimens of most of these genera that we can't come close to estimating how large they might have grown. Some of the genera are represented only by single specimens - there is no reason to think that these were necessarily anywhere near the top end of the possible size-range. (Consider a random sample of a dozen or so humans, then think about how much larger the biggest people are than the biggest in your sample.)

We also have the difficulty that it's very hard to judge the heaviest of these animals, because no-one can agree how much they weighed.

With that said, the longest fully-described predatory dinosaur as of this writing is ... fanfare, please ... Giganotosaurus carolinii at 14.5m (47 feet). We can be pretty confident that it's bigger than T. rex because the two known specimens are bigger than any T. rex for which actual measurements are known. For example, the femur of the type specimen is 1440mm long, compared with about 1380mm for ``Sue'' - a 4% difference. And comparisons of the dentaries of the two known Giganotosaurus indicate that the second specimen is perhaps 8% larger than the type specimen. So Giganotosaurus is almost certainly the biggest predator we have today.

This of course comes with a proviso that new specimens of T. rex, Acrocanthosaurus and/or Currie & Coria's new Patagonia beastie may surpass it at any moment. And then, of course, someone may well find another Giganotosaurus that's bigger again. And so it goes.

By way of a cautionary tale, it's worth reading the ``Which is the largest species of crocodile?'' article in the Crocodilian Biology Database FAQ - see www.flmnh.ufl.edu/natsci/herpetology/brittoncrocs/cbd-faq-q2.htm. This illustrates the difficulty of sifting fact from fiction even when dealing with extant species for which which we can observe numerous fully articulated specimens! Given that dinosaurian remains are so much more fragmentary, it shouldn't surprise us that we run into similar problems when trying to establish which are the biggest dinosaurs. Caveat everyone.

It's interesting to note that there are serious ``biggest predator'' contenders from four different families:

• Allosauridae (Giganotosaurus, Carcharodontosaurus, Allosaurus, Acrocanthosaurus, the new Argentinian Carcharodontosaur and the Monster of Minden)
• Tyrannosauridae (T. rex)
• Spinosauridae (Spinosaurus)
• Megalosauridae (Torvosaurus)

The fact that all these families' largest known representatives are roughly the same size (forty feet in length, give or take) hints that they may all be approaching some fundamental bio-mechanical limit for bipedal carnivores.

Then again, there's a long history of new discoveries breaking through such supposed barriers - remember the ``absolute twenty-foot limit'' on Pterosaur wingspans, which was orthodox right up until they started finding forty-footers? :-) So we should probably not be too quick to jump to conclusions here!

For some nice illustrations of predator sizes, see Gavin Rymill's page at gavinrymill.com/dinosaurs/carnivores

What was the smallest dinosaur?

Question

Answer

What was the fastest dinosaur?

Question

Answer

How Brachiosaurus drink without its head exploding?

Question

Answer

Why do mass estimates vary so much?

Question

Answer

1. Make a scale model, measure its volume, scale it up to life size and multiply by an estimate of the animal's density;

2. Measure the cross-sectional area of load-bearing bones and interpolate on a graph of area-vs-mass for known animals; (Anderson, J.F., Hall-Martin, A., and Russell, D.A., 1985. Long-bone circumference and weight in mammals, birds and dinosaurs: Journal of Zoology, v. 207, p. 53-61.)

3. A new method (see Per Christiansen's Dinosaur Biomechanics chapter in the recent Scientific American book) in which you basically draw the animal, cut the picture into slices and estimate its mass from, er, the area of the picture. Or the volume of cones. Or something.

Method 1 is obviously succeptible to the interpretation of the model-maker. The ``classic'' mass estimate of 80 tons for Brachiosaurus comes from Colbert's 1962 application of method 1 to a model which Matt Wedel describes as ``morbidly obese. It looked like a freakin' Macy's parade balloon. The limb muscles go well beyond the boundaries of the girdles, a sure sign that someone was just throwing clay on an armature without doing a musculoskeletal reconstruction first.''

R. McNeil Alexander applied the same technique to rather better Brachiosaurus model from the British Museum of Natural History, arriving at an estimate of 46 tons; and Greg Paul has done something similar with his own bones-and-muscle reconstruction and reached an estimate of ``only'' 32 tons.

There is another difficulty with method 1: we don't know the density of dinosaurs. Colbert estimated a density close to 1 (i.e. the same as water) based on that of crocodiles, because they are related to dinosaurs. But sauropods are morphologically very distant from modern crocodiles! While limb bones are typically very solid (no marrow cavity), sauropod vertebrae, particularly those of larger species, tend to be extensively pneumatic. To cite Matt Wedel again, his guess at Argentinosaurus density (and so, I imagine, most large sauropods) is 70-75% - but that's based on the assumption of a much more extensive air-sac system than most people seem prepared to believe in. Still, any figure in the range 70-100% seems credible.

Method 2 has its own obvious problem - real animals don't stay on or even very close to the ``best line'' through the points you get by plotting limb-bone cross-sectional area vs. mass. For example, on the basis of such a ``best line'', you'd expect elephants to have thicker leg bones than they actually have, and rhinos to have thinner bones. This variation reflects the fact that different animals have different degrees of athletic ability. So method 2 is probably not good for much better than a within-a-factor-of-two estimate. For what it's worth, Anderson et al. used this method to estimate a Brachiosaurus mass similar to Greg Paul's 32 tons.

Method 3 is succeptible to the same kind of artist's-impression problems as 1, plus it seems inherently less reliable, as it depends more on guesswork concerning the third dimension. The truth is, I don't fully understand Christiansen's explanation of this method, but it does seem to involve a lot of intuition.

Finally, to clear up the 180-ton Brachiosaurus estimate: this is actually for ``Ultrasauros'', which at the time of the estimate was thought to be a large brachiosaurid<sup>[1]</sup>. In his otherwise wonderful book Dinosaurs, Spitfires and Sea Dragons, Christopher McGowan's reaches this staggering number by considering the classical 80-ton estimate for vanilla Brachiosaurus, observing that the ``Ultrasauros'' bones are 1.3 times the size of those in well-known Brachiosaurus specimens, and multiplying 80 tonnes by 1.3³, which is about 2.2.

Notes

[1]

This history of ``Ultrasauros'' is a long and stupid one, but here it is in a nutshell. In 1972, James Jensen discovered two big, new sauropods from the Dry Mesa quarry, Colorado: Supersaurus, a diplodocid, and Ultrasaurus, a brachiosaurid. But before he got round to formally publishing the new names, Haang Mook Kim (1983) described a new Korean sauropod as being a species of Ultrasaurus - thereby inadvertently establishing the name formally as pertaining to his sauropod, which subsequently turned out to be a different (and much smaller) animal.

This left Jensen in the strange position that his own animal couldn't be known by its own name, which was preoccupied by Kim's sauropod. Faced with this situation, he simply shrugged and named his animal Ultrasauros (1985) instead.

So far so weird. But wait - there's more! Then it became apparent that the holotype of the new taxon - a dorsal vertebra - was in fact from Supersaurus, the diplodocid discovered at the same time. Which meant that ``Ultrasauros'' because a junior synonym of Supersaurus.

The remaining ``Ultrasauros'' material - a scapulocoracoid - is now thought to represent merely a large Brachiosaurus - about 15% larger than the specimen in the Humbolt museum (although that's a composite.) Apparently, it's no larger than the biggest of the Tendaguru Brachiosaurus specimens. [back]