|Scientific Name||Carcharocles Megalodon|
|Species||†C. megalodon (extinct)|
|Size||15-20m (49-65ft) in length|
|Weight||~50 metric tons|
Carcharocles megalodon represents the largest predator ever to exist on the planet. According to a study by Pimiento & Clements (2014)1 the species lived up until the end of the Pliocene, around 2.6 million years ago (mya). When first discovered, C. megalodon was placed into the same genus as the great white shark (Carcharadon carcharias), but since then other studies such as Nyberg et al. (2006)2 place the species into the genus of Carcharocles and is now more recognised within the scientific community.
This new take on phylogeny places the species C. megalodon into the Lamniforms, commonly known as the Mackerel Shark group. Indeed, more recent phylogenetic studies have actually linked C. megalodon to the genus Otodus, and extinct mackerel shark from the Eocene (Ehret et al. 2009)3. Both genera fall into the family of Otodontidae, otherwise known as the megatooth sharks4. From tracing back through the phylogeny presented by Ehret et al. it is clear that the closest relatives of C. megalodon are the members of the mako shark family (Genus: Isurus), followed by C. carcharias. Studies actually show that Otodontids increased drastically in size over time up until C. megalodon, which was by far the largest of them all (figure 1). From using these phylogenetic studies, and using present relatives as a template, it is possible to map out how the largest shark ever would have survived, hunted and even how it became extinct.
Short on time? Skip right to the megalodon facts.
The size of C. megalodon is still one of the greatest debates in marine palaeontology. Alike all chondrichthyan, the skeleton of C. megalodon was cartilaginous6, meaning that fossilisation of the bones rarely occurred7, and size estimates thus cannot be accurate. Some central vertebrae have been found of the animal, but the majority of finds are from the teeth of the animal. This means that teeth offer the best chance of reasonably estimating the size of the animal.
A recent study from Pimiento & Balk (2015)5 used the tooth crown height (CH) in order to calculate the total length (TL) of C. megalodon. This was done through the model given by Shimada (2003)8, which used C. carcharias ratios in order to give a reasonable TL. This was done as C. carcharias is believed to be the most similar extant species to C. megalodon. What made this study far more interesting than others was that it looked at how C. megalodon changed in anatomy across the world and through time, picking out both the limitations on growth. Pimiento & Balk also showed the way in which megatooth shark teeth changed in size and appearance throughout history. The results of the study showed that the average TL of C. megalodon was 10.2m, with the largest size being just over 17m. However, it was common that more larger specimens were found than smaller, which the authors based upon the likely large prey items (see section ‘Prey and Hunting’).
The most interesting find however was how the sizes changed across the world. With absolute latitude there was no significant difference in TL, but when looking at the different TL of individuals from different hemispheres and oceans, there was a significant difference in TL. The study found that, on average, larger individuals were found from the southern hemisphere. This was also true when comparing the Atlantic and Pacific, with larger specimens being present within the latter. This was most apparent during the Miocene, which is the time when cetacean groups were properly blooming. The findings of this study are likely due to the presence of cetaceans controlling how the size of C. megalodon changed across the world. Further study has to be done on the cetacean species living within these areas to confirm. Most importantly however, this groundbreaking study showed that the sizes of C. megalodon remained constant throughout geologically.
Prey and Hunting
Unlike most extinct species, perhaps one of the biggest evidence for C. megalodon comes from the fossils of its prey. Traumatic attacks shown in cetacean fossil records are numerous. Such an incident was described by Kallal et al. (2012)9, where a Pliocene cetacean rib fossil from North America was shown to be attacked by a super-predator. Although the bite did not kill the whale, the wound shows signs of infection which likely killed the animal within a matter of weeks. Kallal et al. did not confirm the identity of the attacker, but the most realistic culprit from the fossil formation is C. megalodon.
Indeed, other fossil evidence has revealed the trophic interaction between C. megalodon and cetaceans, with Aguillera et al. (2008) showing that teeth were found in association with carcasses10. Whales were not the only large prey item for C. megalodon, and fossil evidence showed that it also fed on other large marine species such as turtles (Aguillera & Aguillera. 2004)11 and pinnipeds (Allmon et al. 1996)12, making their diet very similar to extant species of raptorial sharks.
How C. megalodon hunted is a mystery, and very little studies have been conducted on its behaviour. Riordon (1999)13 showed that the majority of documented C. megalodon attacks were on to the integral parts of cetaceans, such as the ribcage. This is concordant with the evidence found by Kallal et al., suggesting that the prey would die due to a rupture in their internal organs. It also explains why the teeth of C. megalodon are so much thicker than modern counterparts. Alike all Lamniform sharks, the prey would also experience a high level of blood loss due to the serrations on the tooth, which, entwined with the sheer power that a predator of that size had, would make for a devastating strategy. In fact, Wroe et al. (2008)14 conducted a study on bite-forces of the animal based upon C. carcharias. It found that C. megalodon likely had a bite-force of around 108,000N, which almost was as strong at Tyrannosaurus rex15. It is also likely that alike C. carcharias, C. megalodon would have attacked from below in order to surprise the prey.
C. megalodon lived an exceptionally long time for a super-predator, spanning almost 14 million years1. Why it became extinct has remained a mystery ever since its discovery, with numerous opinions being suggested. As aforementioned, the Miocene was the period of time where cetaceans thrived, especially the great whales. However, evidence from Lambert et al. (2010)16 suggests that these were beginning to fall in numbers towards the end of the Miocene. Indeed, C. megalodon was clearly a specialist that hunted large prey, and by removing them from the ecosystem meant that they could not eat enough in order to survive with such an enormous size.
Extant cetacean species also suggest other issues. Multiple great whales now spend a great deal of time in polar-regions (MacKay et al. 2016)17 and so would have been out of reach for a shark that would likely have preferred a more tropical climate based on Lamniform modern counterparts. It could therefore be argued that perhaps this caused a decline in food reserves for C. megalodon, causing it to be pushed back in numbers. It is also interesting to note the date of which C. megalodon became extinct. According to Pimiento & Clements (2006)1, the last trace of C. megalodon in the fossil record is around the same time as the dawn of the Quaternary Glaciation, around 2.58mya19.
Indeed, sharks today have circulatory systems that allow them to maintain a constant body temperature, however, such a cooling in the Earth’s Oceans would have been catastrophic. Oxygen isotopes indicate that sea-surface temperature (SST) within the Atlantic during the Quaternary Glaciation could have been almost 10–15 °C less than they were at present in July18. This not only would have been difficult to maintain homeostasis for C. megalodon, but also likely would have affected multiple food-source animals.
General Megalodon Facts
- The Megalodon is an extinct species of shark from the Cenozoic Era, living approximately 1.5 to 2.6 million years ago
- At an estimated length of 45 – 60 ft. long, it is the largest prehistoric shark to have ever existed
- They are believed to have weighed as much as 100 tonnes
- Huge 7 inch teeth have been recovered from across the globe, a true testament to their sheer size
- They are considered to have the most powerful bite of any creature that ever lived
- This powerful bite proved more devastating than efficient when it came to feeding
- Megalodon feasted on prehistoric whales, dolphins, fish and giant turtles
- It could easily swallow a person whole
- Pimiento, C., & Clements, C.F. (2014). When did Carcharocles megalodon become extinct? A new analysis of the fossil record. PloS one, 9, p.e111086.
- Nyberg, K.G., Ciampaglio, C.N., & Wray, G.A. (2006). Tracing the ancestry of the great white shark, Carcharodon carcharias, using morphometric analyses of fossil teeth. Journal of Vertebrate Paleontology, 26, pp.806-814.
- Ehret, D.J., Hubbell, G. and MacFadden, B.J. (2009). Exceptional preservation of the white shark Carcharodon (Lamniformes, Lamnidae) from the early Pliocene of Peru. Journal of Vertebrate Paleontology, 29, pp.1-13.
- Ehret, D.J., & Ebersole, J. (2014). Occurrence of the megatoothed sharks (Lamniformes: Otodontidae) in Alabama, USA. PeerJ, 2, p.e625.
- Kriwet, J., Mewis, H., & Hampe, O. (2015). A partial skeleton of a new lamniform mackerel shark from the Miocene of Europe. Acta Palaeontologica Polonica, 4, pp.857-875.
- Ashhurst, D.E. (2004). The cartilaginous skeleton of an elasmobranch fish does not heal. Matrix Biology, 1, pp.15-22.
- Shimada, K. (1997). Skeletal anatomy of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli from the Niobrara Chalk in Kansas. Journal of Vertebrate Paleontology, 4, pp.642-652.
- Shimada, K. (2003). The relationship between the tooth size and total body length in the white shark, Carcharodon carcharias (Lamni- formes: Lamnidae). Journal of Fossil Research. 35, pp. 28–33.
- Kallal, R.J., Godfrey, S.J., & Ortner, D.J. (2012). Bone reactions on a pliocene cetacean rib indicate short‐term survival of predation event. International Journal of Osteoarchaeology, 3, pp.253-260.
- Aguilera, O.A., García, L., & Cozzuol, M.A. (2008). Giant-toothed white sharks and cetacean trophic interaction from the Pliocene Caribbean Paraguaná Formation. Paläontologische Zeitschrift, 2, pp.204-208.
- Aguilera, O.A. & Aguilera, D.R. (2004). Giant-toothed white sharks and wide-toothed mako (Lamnidae) from the Venezuela Neogene: their role in the Caribbean, shallow-water fish assemblage. Caribbean Journal of Science, 3, pp.368-382.
- Allmon, W.D., Emslie, S.D., Jones, D.S., & Morgan, G.S., (1996). Late Neogene oceanographic change along Florida’s west coast: evidence and mechanisms. The Journal of Geology, pp.143-162.
- Riordon, J. (1999). Hell’s teeth. New Scientist. 32.
- Wroe, S., Huber, D.R., Lowry, M., McHenry, C., Moreno, K., Clausen, P., Ferrara, T.L., Cunningham, E., Dean, M.N. and Summers, A.P. (2008). Three‐dimensional computer analysis of white shark jaw mechanics: how hard can a great white bite?. Journal of Zoology, 4, pp.336-342.
- Bates, K.T. and Falkingham, P.L. (2012). Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics. Biology Letters, p.rsbl20120056.
- Lambert, O., Bianucci, G., Post, K., de Muizon, C., Salas-Gismondi, R., Urbina, M. and Reumer, J. (2010). The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru. Nature, 466, pp.105-108.
- MacKay, M.M., Würsig, B., Bacon, C.E. and Selwyn, J.D., 2016. HUMPBACK WHALE (Megaptera novaeangliae) HOTSPOTS DEFINED BY BATHYMETRIC FEATURES OFF WESTERN PUERTO RICO. Canadian Journal of Zoology.
- Daniel F. Belknap. (2015) .Quaternary. Available at: https://www.britannica.com/science/Quaternary [Accessed 10 August 2016].