Time of the Titans - Which Was the Biggest Dinosaur of All Time?
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Giants Amongst the Dinosaurs - Which was the Biggest Dinosaur of All Time?
One of the most interesting aspects of dinosaurs for children is learning all about how diverse this group of reptiles actually were. For example, to date there have been over 1,000 different species formally named and described. A great many of these known species were quite small, the idea that all dinosaurs were huge is a bit of a misnomer, and dinosaur with 500 teeth which love to have a huge and spectacular dinosaur display often give the wrong impression. As dinosaurs evolved, they filled virtually every niche in the food chain, just as terrestrial mammals do today. If land mammals can range in size from a shrew to an African elephant, then it is not surprising to learn that dinosaurs varied in size too.
But what about the really big dinosaurs? Children love to learn facts and figures about these prehistoric animals and amongst their favourite questions is to enquire which was the biggest dinosaur of all time? To identify the giants among the dinosaurs is a relatively easy task. There is one particular group that grew much bigger than every other known type of dinosaur - indeed some of the members of this group were undoubtedly the biggest, the longest and the heaviest land animals that have ever roamed planet Earth.
A well-known dinosaur such as Triceratops (Triceratops horridus) was big. The largest species of Triceratops is estimated to have been around nine metres in length and it might have weighed as much as seven tonnes. If this species of dinosaur were around today it would be classed as the largest land living animal, with only the African elephant (Loxodonta africana) to rival it. However, Triceratops would have been dwarfed by most of the members of the Sauropoda, a group of long-necked, long-tailed, lizard-hipped dinosaurs, representatives of which can claim to be the biggest land living animals known to science.
Introducing the Sauropods
Put simply, the Sauropods (the name means "lizard foot") were Saurischian, that is belonging to the lizard-hipped clade of dinosaurs that also included the mainly carnivorous Theropods. These plant-eating dinosaurs had small heads, long necks and tails with massive bodies. Their weight was supported by four trunk-like legs and these animals were slow-moving, ponderous creatures. Some of their kind evolved dermal armour and one or two unusual genera even had tail clubs and spikes, similar to the armoured dinosaurs such as the Stegosaurs and the Ankylosaurs. These dinosaurs appear in the fossil record in Upper Triassic strata and they survived right up until the end of the age of dinosaurs. Sauropods would have been familiar to the likes of Triceratops and Tyrannosaurids such as Tyrannosaurus rex. It was the Victorians who first marvelled at the size of these dinosaurs. The first really big dinosaur fossil bones being put on display during the reign of Queen Victoria and it is from this point onwards that the debate as to which was the biggest dinosaur really got going.
Defining the Biggest Dinosaurs
There are many problems with trying to identify which was the biggest of the Sauropods. For a start, most of these colossal creatures are known from only a few fragmentary and far from complete skeletons. Although the size of a dinosaur can be deferred from a few bones such as the femur (thigh bone) using a process related to comparative anatomy it is not precise. The other problem is, new species are being discovered all the time and this can lead to changes in size estimations. Indeed, once a new dinosaur is named and described the resulting press publicity can lead to some inaccurate size estimates becoming highlighted in the media. It seems that adults and children too are interested in record breakers. We recall working on some papers related to the fossilised track way of a large Sauropod found in Upper Jurassic aged rocks in France. The tracks consisted of several metres of clearly defined and very large footprints, some more than a metre in diameter. By the time the press agencies had got hold of the story and seen some of the photographs, there was speculation that the dinosaur that walked over the soft mud that preserved their tracks was one of the biggest of all time. This is not easy to confirm when you have only got the footprints to go on. The soft mud would have been easily compacted by the animal's weight and the tracks distorted somewhat as a result. The fossilisation process would also have distorted the prints, and perhaps their size was overestimated in the press pictures as only the biggest, clearest prints were photographed.
The Biggest Dinosaurs of All Time - The Contenders
Let us start with the current record holder, the dinosaur officially described as the biggest known to science, at least for the time being. This honour goes to the South American Sauropod Argentinosaurus (Argentinosaurus huinculensis). This huge dinosaur was formally named and described in 1993. It is only known from a few fragmentary bones, including a femur and some vertebrae, (backbones). The fossils were found in Argentina, hence the name. The tallest vertebrae are over 1.2 metres high. In comparisons with better known Sauropods size estimates for this dinosaur have been made. These estimates vary considerably, with some scientists suggesting that this dinosaur may have been over forty-five metres long and weighing something close to seventy tonnes. Other more conservative estimates as to the size of this animal have been made, with a length of a little over one hundred feet being agreed upon by some palaeontologists. It is certainly, true that this Cretaceous giant was an enormous animal, but until more fossils are found the true size of this dinosaur can only be estimated. A number of museums have capitalised on the popularity of the largest dinosaurs and prepared mounted replicas of this particular giant. The largest of these museum exhibits measures over thirty-five metres in length, but here again, without more fossil evidence this display is largely speculative.
Other South American Contenders
There are other fragmentary remains of really big, South American Sauropods (Titanosaurs like Argentinosaurus), to consider. A femur (thigh bone) ascribed to a dinosaur known as Antarctosaurus measures over 2.3 metres in length, suggesting a dinosaur with a length in excess of forty metres. Other South American giants, such as a contemporary of Argentinosaurus, known as Andesaurus (Andesaurus delgadoi) is known from a few very large tail bones. Again size estimates put this particular dinosaur in the over forty metre bracket.
"Bruhathkayosaurus" - The Controversy
Fragmentary remains of a truly huge Titanosaurid Sauropod were discovered in southern India during the 1980s. At first scientists thought that the fossils were from an enormous meat-eating dinosaur. However, in 1995 the fossils were reclassified as belonging to a Sauropod, simply because no other animal was known to be so big. A tibia (lower leg bone), ascribed to this dinosaur was more than 1.25 times the size of the equivalent bone ascribed to Argentinosaurus. Based on scaling up using this single bone as evidence, the dinosaur from India known as Bruhathkayosaurus (Bruhathkayosaurus matleyi) would be the largest dinosaur known to science. However, the fragmentary nature of the fossils found to date are keeping this particular specimen out of the record books.
Diplodocus and the Big Sauropods from the United States
Some of the best known long-necked dinosaurs lived in what was to become the United States. Dinosaurs such as Diplodocus and Apatosaurus (formerly known as Brontosaurus). However, these dinosaurs were not as wide-bodied as their Titanosaur relatives and not contenders for the biggest, that is the heaviest dinosaur of all time. However, there is one mysterious fossil discovery from the United States that could rival the South American dinosaurs in size. In 1878, the American palaeontologist Edward Cope described a one and a half metre long portion of a vertebrae from Upper Jurassic strata from Colorado. The complete bone would have been something like two and a half metres in length, making it the biggest back-bone fossil ever found. Cope named this dinosaur Amphicoelias fragillimus and some scientists have estimated that this dinosaur may have reached lengths in excess of fifty-five metres, stood nine metres high at the hips and weighed something approaching one hundred and fifty tonnes. Unfortunately, the bone is no longer around to be studied, the lack of knowledge regarding fossil bone preservation meant that this fossil crumbled into dust, it is only known from drawings made at the time. Still, if the size estimates are to believed then this dinosaur from the western United States could claim to be the biggest of all time.