Here There Be Giants
I've been wanting to check out the Giants exhibition at the National Museum of Scotland for a while now and, since the exhibition will be closing soon, I knew I needed to get a move on. Giants, designed and produced by the Royal Belgian Institute of Natural Sciences, exhibits life-sized sculptures of prehistoric megafauna (giant animals) that incorporate fossils into the design. The exhibition includes two marine species that I specifically want to talk about.
The real leviathan
Livyatan melvillei is an extinct relative of the sperm whale (Physeter macrocephalus) that lived about 9.9 million years ago to, potentially, 5 million years ago. At a body length of 13.5 to 17.5 metres, Livyatan was not much bigger than a modern sperm whale but, once you look at their teeth, you realise there's a clear winner on size. Just look how this Livyatan melvillei tooth compares to that of a sperm whale and a killer whale (Orcinus orca).
There's another clear difference between Livyatan and a sperm whale when we compare the jaws. Let's take a look at Moby's skull, another exhibit in the National Museum of Scotland's collection, pictured below. You'll notice Moby only has teeth in his lower jaw. When he was alive, these would have fit perfectly into sockets in his upper jaw, ideal for gripping squid so that it can't slip away.
Compare that with the skull of Livyatan melvillei pictured below and we see that Livyatan notably has large interlocking teeth in both the upper and lower jaws, providing the efficient bite it needed to prey on seals, dolphins, and other whales, with the tilted front teeth providing grip. The skull also gives some clues as to what Livyatan would have looked like, indicating a short, wide snout, with the large openings on the side suggestive of its incredible jaw muscles.
L. melvillei fossils have been found in Chile and Peru but it is thought that the species would have had a wide global distribution. They were extinct by the early Pliocene around 5 million years ago, when there was a global cooling trend that caused baleen whales to increase in size and decrease in diversity, depleting Livyatan's main food source. This is a fate that parallels that of our next exhibit, Otodus megalodon.
The biggest shark that ever lived
Otodus megalodon, or simply megalodon (meaning big tooth), was a species of mackerel shark that lived from the early Miocene around 23 million years ago to the early Pliocene around 3.58 million years ago. As is the case with all sharks, megalodon had a skeleton made of cartilage rather than bone, making fossils (other than their teeth) rare. However, from the few vertebrae that have been found, their position in the spine can be plotted, like in the pictures, allowing scientists to estimate the shark's body length, with this particular individual being about 16 metres. To put that in perspective, the largest confirmed size for a great white shark (Carcharodon carcharias) is 6.1 metres.
Reaching over 18 cm in slant height, megalodon had the largest teeth of any known shark species. These are serrated along both edges of the blade of the tooth, allowing them to cut through blubber and bone. As shown in the model below, like modern sharks, megalodon had rows of teeth in its jaw, ensuring that old and worn teeth were constantly being replaced with new ones. Maintaining a full set of teeth in this way, combined with its size and its powerful jaws, would have made megalodon a highly competitive apex predator in marine ecosystems.
Megalodon fossils are widely distributed, with specimens found in Europe, Africa, Asia, Australia, and the Americas. This suggests the shark inhabited a range of marine habitats all over the world, making it likely that megalodon would have shared hunting grounds with Livyatan for a time, competing for similar prey of cetaceans. This means megalodon was faced with the same challenges as Livyatan during the early Pliocene, with food sources being insufficient to sustain Otodus megalodon populations. At this time, many marine giants died out, changing the oceans forever.
The Giants exhibition is open till Monday 14 September so you still have a little time if you want to see it for yourself. As well as the two marine species I've highlighted here, there are a wide variety of terrestrial animal exhibits on display, including Titanoboa (the largest snake to ever live), a giant ground sloth, and a woolly mammoth. The exhibits are definitely worth seeing in person to appreciate the sheer scale of the creatures that once lived here.
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