MAMMAL NAMES | 'Largest Animals Ever'? Part I:

Ireland's Blue & Fin Whales VS the Dinosaurs

Our recent explorations of Ireland’s baleen whales have inundated us with a flood of names and titles related to the particular forms of these mighty cetaceans. However, there is one title that stands head and shoulders above all others – that of ‘largest animal ever’. This, the greatest heavyweight title in the animal kingdom, has been bestowed upon that colossal species, the blue whale, while its fellow balaenopterid that also cruises through Ireland’s seas, the fin whale, has had the title of ‘second largest animal ever’ conferred upon it by some experts. Over the next two months, then, we will investigate the claims of these two whales to such exalted titles, in the process meeting a menagerie of mighty monsters from the last 200 million years and more, a number thought to have lived in Ireland or its seas, and many of which themselves have fantastic names and titles related to their titanic dimensions. And, of course, we can begin this month with a look at the greatest beasts ever to live on land – the dinosaurs.

Before we begin this great age-spanning quest for giants, though, it might be best to first briefly reacquaint ourselves with just how large the blue and fin whales are.

Well, last month we saw that the blue whale and fin whale are indeed the largest and second largest whales, respectively, in the world’s oceans, and we encountered many fascinating facts about the gigantic form of the blue whale in particular. But we could add even more to this roster of amazing facts about their great size.

For instance, adults can eat as much as a staggering five tonnes of krill a day – that is almost the weight of a male African elephant, which, at an average of six tonnes, is the largest mammal on land today. The young of this leviathan too are insatiable beasts, newborns suckling so much of their mother’s extremely rich milk that they can put on 90 kilograms in weight per day, which is about the same as adding the weight of Ireland’s rugby great Johnny Sexton to their bulk daily. With such incredible feats of ingestion, a young blue whale can add around 17 tonnes to its birth weight of 2.5 tonnes by the time it is six or seven months old.

Blue whales, then, are absolutely gigantic, and, as we saw last month, they are thought to be able to reach a maximum weight of 180 tonnes, equivalent to the weight of 30 male African elephants. And though the fin whale is not quite as large, it is still a truly monstrous form, with maximum weight estimates ranging from 90 to 117 tonnes, the latter figure almost equal to the weight of 20 male African elephants.

So, it is clear that the blue whale and fin whale are certainly far, far larger than the largest animal on land today, the African elephant. But how do they fare against the greatest land animals when all the extinct giants are included?

When it comes to the land mammals, they fare quite well, as the largest land mammal to ever live, the Asian straight-tusked elephant, Palaeoloxodon namadicus – which we have previously encountered – weighed only 22 tonnes. Although this is an incredible weight compared to the living African elephant, it is still far lower than the maximum weights of the blue and fin whales, the former weighing around eight times as much and the latter somewhere between four and five-and-a-half times as much.

The largest land mammal to have ever lived cannot hold a candle to the blue and fin whales swimming in Ireland’s seas today, then, and their claims to the titles of ‘largest animal ever’ and ‘second largest animal ever’ are unshaken by their comparison to Palaeoloxodon namadicus. But, as we all know, the mammals are far from the largest animals to have roamed the Earth, and in very ancient times the continents played host to a group of reptiles whose members included many true titans – those ‘terrible lizards’, the dinosaurs!

The largest of the dinosaurs were those massive, four-legged, long-necked herbivores called sauropods, whom most of us will know best in terms of names like Brachiosaurus or Diplodocus. ‘Sauropod’ itself ultimately derives from two Greek words, sauros, meaning ‘lizard’, and pous or pod, meaning ‘foot’, and sauros is an element in a great many dinosaur names, sometimes in abbreviated form as sauro or saur, or often in the Latinised form –saurus at the end of names.

Although dinosaur fossils have been found in Ireland, these do not include ones of sauropods. However, fortunately, many fossils of sauropods have been found in Britain, and some of these date from times that this land would have been firmly joined to Ireland, so these sauropods may have been members of the Irish fauna too.

Some of the British sauropods appear to have belonged to a genus called Cetiosaurus, which means, neatly considering our subject matter, ‘whale-lizard’, this name derived from the fact that when the first fossils of this beast were discovered they were thought to belong to a marine creature. However, the largest known sauropod from Britain is a relative of Brachiosaurus that lived around 130–125 million years ago in the early part of the Cretaceous period (c. 145–66 million years ago), a fossil of which was found on the fossil-rich Isle of Wight in the very south of England in 1992.

This sauropod does not have a name, as its genus and species is indeterminate, but what is clear is that it was a true giant. Based on the size of the fossil, which is a massive neck vertebra, it is thought that this relative of the 50-tonne Brachiosaurus would have exceeded 20 metres in length, and there have been claims that it weighed as much as 40–50 tonnes. However, it is likely that it was at the lower end of this range, if not even lower, as the holder of the title of ‘Europe’s largest dinosaur’ is a sauropod called Turiasaurus riodevensis which lived in Spain around 145 million years ago that is said to have weighed 40–48 tonnes.

Indeed, the 2004 study that described this British sauropod concluded that it may have been comparable in size to its fellow brachiosaurid Giraffatitan (‘titanic giraffe’) which lived in Tanzania in the late Jurassic period, around 150 million years ago, that measured 25 metres in length and 25–35 tonnes in weight.

So, although not perhaps as heavy as 40–50 tonnes, the largest sauropod to ever inhabit Britain, and possibly Ireland, could still have weighed up to as much as around six male African elephants, a phenomenal size. This massive sauropod was still far from challenging the blue whale or fin whale in terms of size, though, so we must jet off to other lands to meet even larger sauropods to see how they measure up.

We have already met the British sauropod’s brachiosaurid relative Giraffatitan, and for much of the twentieth century up to the 1990s this African sauropod held the title of ‘largest dinosaur ever’. However, in recent decades, across the world the earth has surrendered fossils of far, far larger sauropods. One of these was, again, a relative of Britain’s largest sauropod, a brachiosaurid with the impressive name of Sauroposeidon, Poseidon being not only the god of the sea that the blue whale and fin whale swim in, but the god of earthquakes.

And the ground would certainly have quaked under the feet of Sauroposeidon when it roamed across North America in the early Cretaceous 125–100 million years ago, as this behemoth is thought to have weighed up to 50–60 tonnes. It was also possibly the tallest dinosaur, its 12-metre-long neck being the longest of any vertebrate and contributing hugely to its overall height of around 17 metres. To put that in context, an adult human would have to stand on top of three giraffes stacked one on top of the other just to be able to touch the head of Sauroposeidon.

However, it is not in North America but South America that we meet many of the very greatest sauropods, and these all seem to have lived later in the Cretaceous than Sauroposeidon, between around 100 and 66 million years ago. Very suitably, these great sauropods belong to a group called Titanosauria, named after the Titans in Greek mythology (although it should be noted that not all members of this group were massive, as it also contained the smallest sauropods known). The titanosaurs were, in fact, relatives of the brachiosaurids, with whom they and a few others comprised the larger group Titanosauriformes.

In any case, the titanosaurs include some seriously big forms. One of the most recently discovered is Dreadnoughtus, which lived in Argentina, in the southern tip of Patagonia, around 77 million years ago. Its name comes from the Old English dreadnought, which means ‘fearing nothing’ – a reference to the gigantic size of this beast who had little to fear from predators, and also to the dreadnought battleships of the early twentieth century, two of which were in service in the Argentine navy.

In the 2014 paper describing this sauropod, it was claimed that it measured around 26 metres in length and weighed over 59 tonnes. However, a study a year later concluded that it may have been 20–25 tonnes lighter than this. Whatever the truth of this is, though, the other truly massive sauropods from South America we will look at are thought to weigh over 60 tonnes, and they too, like Dreadnoughtus, come from Argentina.

Indeed, this is reflected in the names of the two largest forms, which lived around 95 million years ago, Patagotitan deriving its name from Patagonia, while the name of Argentinosaurus is self-explanatory. Patagottitan was an absolute monster, thought to have weighed around 69 tonnes, and it was also a contender for longest dinosaur, measuring 35–36 metres in length, or even more according to some estimates. However, Argentinosaurus appears to have been the greatest titan of them all.

Although slightly shorter than Patagotitan, Argentinosaurus still measured around 35 metres in length, and it is thought to have had a great bulky body. Estimates of its weight generally range from 60 to 100 tonnes, and one 2018 article from The Guardian even claimed that it weighed 120 tonnes! But while this may well be far overblown, even the more sober estimates generally rest around the 75-tonne mark, conferring the title of ‘largest dinosaur ever’ on Argentinosaurus.

The largest dinosaur ever, then, does not seem to remotely trouble the claim of the blue whale to the title ‘largest animal ever’, although it should be noted that this is only true when it comes to weight. If we were to determine largest in terms of length, both Patagotitan and Argentinosaurus and a few other giant sauropods would qualify as larger than the blue whale, which even at the dubious highest recorded length of 33.6 metres would not be able to match them. Of course, the fin whale too would lose its claim to the title of ‘second largest animal ever’, and this could also happen in terms of weight if the very highest weight of 120 tonnes for Argentinosaurus turned out to be true, but this is unlikely.

So, the great Argentinosaurus, king of the dinosaurs, does not seem to be quite able to wrest the crown from either the blue whale or fin whale in terms of weight. But before we leave the dinosaurs altogether, there are a few controversial fossils we must meet, as these have led to claims in the past for the existence of dinosaurs of such enormous size that they could have toppled the blue and fin whales from their perch.

The first of these is a 1.5-metre-high incomplete back vertebra found in 1878 which was ascribed to a species called Amphicoelias fragillimus. Controversy surrounds this specimen as it was subsequently lost and only the original drawings of it survived. Based on these drawings, though, a number of experts have concluded that this dinosaur reached incredible dimensions, one estimate from 1994 settling on a length of 40–60 metres and a weight of 100–150 tonnes, while a more recent one from 2006 reached a similar conclusion, producing an estimate of 58 metres in length and a weight of over 122 tonnes!

These are astonishing dimensions, and a creature of such size would easily have a stronger claim to the title of ‘second largest animal ever’ than the fin whale, while it would be almost twice the length of the blue whale, if we take the longest reported length to be true. However, very recently there has been another twist in the tale.

The man who produced the 2006 estimate of 58 metres and over 122 tonnes, Kenneth Carpenter, re-examined the evidence relating to Amphicoelias fragillimus in 2018 and came to a conclusion of great consequence regarding its affinities. Whereas all earlier estimates of this dinosaur’s size had been based on the understanding it was a diplodocid (whose most famous member is, of course, Diplodocus), Carpenter concluded that it was actually from a related family called Rebbachisauridae. Thus, he removed it from Amphicoelias and placed it in a new genus called Maraapunisaurus, ma-ra-pu-ni meaning ‘huge’ in the language of the Southern Ute, a Native American tribe originally from the area in Colorado where the fossil was found. This was very important, as the body proportions of this sauropod family were quite different, and Carpenter concluded that even if we accept the great size of the specimen, it would still have belonged to a creature only 30.3–32 metres in length.

Maraapunisaurus fragillimus was a gigantic creature, then, but not so big to unseat Argentinosaurus as dinosaur king, nor challenge the blue whale or fin whale. Yet, this is not the only claim that has been made for a dinosaur of absolutely gigantic size.

In 1989, some giant fossils were unearthed in southern India and ascribed to a sauropod called Bruhatkayosaurus, a name derived from the Sanskrit word bruhatkaya, meaning ‘heavy/huge beast’. Based on the reported size of these fossils, in 2001 one amateur palaeontologist, Mickey Mortimer, produced a mind-blowing size estimate for this late Cretaceous beast, concluding it was over 44 metres long and around 160–200 tonnes in weight. This would have made it even heavier than the blue whale! However, Mortimer subsequently retracted the weight estimates and also reduced the estimated length to around 28–34 metres, making Bruhatkayosaurus shorter than Argentinosaurus.

More recent claims have been made for the gigantic size of Bruhatkayosaurus, though. In 2008, the palaeontologist Matt Wedel produced a weight estimate for this sauropod based on a comparison with Argentinosaurus and concluded that it may have weighed up to 126 tonnes. If true, this would, of course, mean that Bruhatkayosaurus would deserve the title of ‘second largest animal ever’, not the fin whale. However, as the fossils of this sauropod have yet to be properly described, no reliable conclusions can be made on the size of this ancient beast. What is more, some think that the fossils themselves are not of sauropod bones at all but of petrified wood – if that turns out to be true, then we have been truly barking up the wrong tree.

Claims for the existence of giant sauropods that were even larger than Argentinosaurus, so-called ‘gigapods’, then, appear to be very flimsy, and it is worth noting that some studies have concluded that due to limiting factors such as the force of gravity, etc., a weight of around 75 tonnes is about the maximum that can be reached by an organism living on land.

So, it seems that on the balance of all evidence, Ireland’s blue and fin whales retain their claims to the titles of ‘largest animal ever’ and ‘second largest animal ever’, even when matched up against the largest of those ancient titans, the dinosaurs, at least in terms of weight. There has never, then, lived on land a creature heavier than these living marine leviathans. So, to find giants that can truly challenge the blue and fin whales, next month we must turn to the ancient waters of their own domain – the sea.