The prehistoric giant Carcharocles megalodon (or Otodus megalodon for some researchers) was the largest predatory shark to swim in Earth’s seas. Scientific evidence indicates that the megalodon lived between 16 million and 2.6 million years ago, becoming extinct at the end of the Pliocene era, when the world’s oceans were much colder than today. hui.
Over the years, several research articles have estimated the size of mega. Its teeth are shaped like large, flat triangles with jagged edges – much like the teeth of living white sharks. White sharks, along with mako sharks and porbeagle sharks all belong to the Lamnidae family and are called “lamnids”.
The close similarities between mega teeth and those of living lamnid sharks is strong evidence that meg was indeed an ancient type of lamnid shark. This premise is important because it forms the basis of how we estimate the size of this ancient giant.
Two museum exhibits recently opened public exhibits featuring spectacular megalodon models: one at the Smithsonian Museum of Natural History in Washington DC and the other at the Western Australian Museum Boola Bardip in Perth.
These models, while both exceptional, do not represent entirely the same shark. So how was each made? And what scientific approaches have been used?
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Make the meghead
The Smithsonian’s megalodon model is a 15-meter full-body reconstruction. The other, at the Boola Bardip Museum, is a beautifully crafted model of a mega head. It was built under the direction of one of us (Mikael) and opened to the public in November.
The shape of the “meghead” is similar to the head of a white shark, but has a shorter and much rounder muzzle. Its coloring features a “counter-shading” with a dark back and a lighter belly – also similar to white sharks, but less contrasting. The greater this color contrast, the easier it is for underwater predators to go unnoticed by prey.
The size of the meghead’s jaw was based on several teeth from a single ancient shark. These specimens allowed us to scale the body size to match the size of the tooth, as well as to match the larger anterior tooth of another megalodon found in Cape Range, Western Australia.
The rest of the head was then modeled in 3D to fit the jaws. The end result was a head that matched a creature about 14m long. It would be the biggest mega shark ever found in Western Australia, but not the biggest overall.
Gorgeous screens make great selfies
The Smithsonian meg model was supervised by Hans-Dieter Sues, an American paleontologist who drew the outline of the shark based on a general plan of the body of a lamnid shark. This was later developed by Bretton Kent, a shark fossil expert at the University of Maryland.
After looking at a small-scale model, the full-size model was built based on a full set of mega teeth assembled by Gordon Hubble, another megalodon expert. Measuring 15m, the final model had to be assembled as modules, as it would not have passed through the doors or corridors of the museum in one piece.
This model is now suspended by cables from the walls and ceiling of the Smithsonian, strategically positioned for visitors to take selfies from a nearby balcony.
Calculating the maximum size
The meghead model in Perth was based on several specimens of specific teeth found locally and overseas, painting an image of a 14m long predator.
However, to calculate the species’ maximum size, we first estimated the maximum jaw size possible for Meg, and then increased it, using the same jaw size to body length ratio as live white sharks.
The maximum mega jaw size can be calculated by increasing the few known “associated dentitions” (several specimens of teeth that were found together and came from a single shark) with the largest tooth ever found.
Once we did that, the size estimate we reached was between 19-20m. And that’s much bigger than most other recent estimates.
The megashark lineage
Scientists have discovered that meg teeth are part of a continuum of species known as the mega-toothed shark line. This is based on the discovery of several thousand fossilized teeth that appear to merge into new shapes over time, indicating the evolution of new species.
The beginning of this lineage began in the Danian stage around 63 million years ago, when the first sharks of the genus Otodus appeared. This is why the megalodon, belonging to this lineage, is now officially classified as Otodus megalodon. That said, the shark has been placed in various genera, including Carcharocles and Procarcharodon, and continues to be the subject of debate.
With an estimated body length of around 4 m, the first Otodus mega-tooth lineage sharks would have been smaller than several other sharks living at the time. So how could they have evolved into the colossus that is Meg?
Kenshu Shimada, a professor at DePaul University, suggested that meg’s enormous size might have something to do with a strange trait in lamnid sharks, namely that their young are eaten in the womb.
This behavior, called “intrauterine cannibalism”, provides an immediate source of nutrition for the growing fetuses and may have resulted in increased growth of the megalodon. That said, it would also have forced mothers to feed themselves more actively, due to the increased nutritional demand of the fast growing young.
It wouldn’t have helped Meg’s survival when global temperatures cooled about three million years ago. The cold snap would have killed much of the meg food sources, ultimately triggering its extinction.
In recent years, coastal limestone outcrops in Western Australia have given rise to several exciting new megalodon teeth. We hope these tell us more about the history of the mega and its variations that swam through the seas of ancient Australia.
This article by John Long, Strategic Professor of Paleontology, Flinders University and Mikael Siversson, Head of Department, Earth and Planetary Sciences, Western Australian Museum is republished from The Conversation under a Creative Commons license. Read the original article.