Latest news with #JeremyMcCormack
CNN
28-05-2025
- General
- CNN
What megalodon really ate to meet its 100,000-calorie daily requirement, according to a new study
Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. CNN — What scientists understand about the voracious feeding habits of the colossal megalodon could be up for some revision. The prehistoric predator that went extinct about 3.6 million years ago was not hunting only large marine mammals such as whales as researchers widely thought, a new study has found. Instead, minerals in fossilized teeth reveal that megalodon might have been an opportunistic feeder to meet its remarkable 100,000-calorie-per-day requirement. 'When available, it would probably have fed on large prey items, but when not available, it was flexible enough to feed also on smaller animals to fulfill its dietary requirements,' said lead study author Jeremy McCormack, a geoscientist at Goethe University in Frankfurt, Germany. The study, published Monday in the journal Earth and Planetary Science Letters, also showed there were regional differences in the giant shark's feeding habits. The finding suggests megalodon would pursue whatever was in local waters, devouring other top predators and smaller prey alike. 'They were not concentrating on certain prey types, but they must have fed throughout the food web, on many different species,' McCormack said. 'While certainly this was a fierce apex predator, and no one else would probably prey on an adult megalodon, it's clear that they themselves could potentially feed on almost everything else that swam around.' Megalodon dispatched its prey with a ferocious bite and lethal, serrated teeth that could reach up to 7 inches (18 centimeters) long — the size of a human hand. The superpredator's teeth — abundant in the fossil record — are what McCormack and his colleagues used to conduct a geochemical analysis, unlocking fresh clues that could challenge megalodon's role as sole king of the ancient seas. Zinc in megalodon teeth It's not the first time that a study has challenged previous knowledge about the enormous sea creature. In fact, many questions remain unanswered about Otodus megalodon — its scientific species name meaning 'giant tooth' — since no complete fossil has ever been discovered. The lack of hard evidence stems from the fact that fish skeletons are made of softer cartilage rather than bone, so they don't fossilize very well. Recent research found that the animal was more warm-blooded than other sharks, for example, and there is an ongoing debate about its size and shape. Scientists who created a 3D reconstruction suggest ed in 2022 that megalodon was about three times as long as a great white shark — about 52 feet (16 meters). However, a March study hypothesized that the megashark was actually much larger — up to 80 feet (24 meters) in length and even longer than the fictional version in the 2018 blockbuster 'The Meg,' which suggested the ancient predator was 75 feet (23 meters) from head to tail. As for megalodon's feeding habits, determining what it ate based on fossil evidence poses challenges, according to McCormack. 'We know that they fed on large marine mammals from tooth bite marks,' he said. 'Of course, you can see bite marks on the bones of marine mammals, but you will not see them if they fed on other sharks, because sharks don't have bones. So there's already a bias in this kind of fossil record.' To glean more about megalodon's prey selection, McCormack and his coauthors looked at the giant shark's fossilized teeth and compared them with those of other animals that lived at the same time, as well as teeth from modern sharks and other predators such as dolphins. The researchers used specimens from museum collections and samples from beached animal carcasses. Specifically, the study team conducted a lab analysis of zinc, a mineral that is acquired only through food. Zinc is essential for living organisms and plays a crucial role in tooth development. The ratio of heavy and light zinc isotopes in the sharks' tooth enamel preserves a record of the kind of animal matter that they ate. Different types, or isotopes, of zinc are absorbed when fish and other animals eat, but one of them — zinc-66 — is stored in tooth enamel much less than another, zinc-64. The ratio between those zinc isotopes widens the further away an animal gets from the lowest level of the food chain. That means that a fish eating other fish would have lower levels of zinc-66 compared with zinc-64, and the fish that eat those fish will have even less zinc-66 compared with zinc-64, creating ratio markers that can help draw up a sequence of the food chain. The researchers found that sea bream, a fish that feeds on mussels and crustaceans, was at the bottom of their reconstructed chain, followed by smaller sharks from the Carcharhinus genus, up to 9.8 feet (3 meters) in length, and extinct toothed whales comparable in size to modern dolphins. Farther up were larger sharks such as the Galeocerdo aduncus, similar to a modern tiger shark, and occupying the top slot was megalodon — but its zinc ratios were not so different as to suggest a massive gap with the lower-tier animals, meaning they might have been part of megalodon's diet, too. 'Based on our new results, we see that it was clear it could feed at the very top, but it was flexible enough to feed also on lower (levels of the food chain),' McCormack said. In addition, the researchers found megalodon was not alone at the top of the food chain but instead shared the spot with other 'opportunistic supercarnivores' such as its close relative Otodus chubutensis and the lesser-known Araloselachus cuspidatus, another giant fish-eating shark. That revelation challenges the assumption that megalodon was the exclusive ruler of the oceans and draws comparisons with the great white shark, another large opportunistic feeder. The finding also reinforces the idea that the rise of the great white may have been a factor in megalodon's extinction, according to paleobiologist Kenshu Shimada, one of the coauthors of the latest study. 'One of the contributing factors for the demise of megalodon has been hypothesized to be the rise of the great white shark, which feeds on fish when young and shifts its diet to marine mammals as it becomes larger,' said Shimada, a professor of biological and environmental sciences at DePaul University in Chicago. 'Our new study, that demonstrates the 'diet overlap' between the great white shark and megalodon, strengthens the idea that the evolution of the smaller, likely more agile and maneuverable great white shark could have indeed (driven) megalodon to extinction.' Megalodon vs. great white shark The new research allows scientists to recreate a snapshot of the marine food web that existed about 20 million years ago, according to Jack Cooper, a UK-based paleobiologist and megalodon expert who wasn't involved with the study. 'The general picture of megalodon has been of a gigantic shark munching on whales,' Cooper said in an email. 'This study adds a new dimension that megalodon probably had a wide range of prey — essentially, it probably ate not just whales but whatever it wanted.' Another interesting find, he added, is that megalodon's diet probably varied slightly between different populations, something observed in today's great white sharks. 'This makes sense and is something we would have probably expected since megalodon lived all over the world and not all of its prey items would have done; but it's wonderful to have concrete data supporting this hypothesis,' Cooper said. The study adds to a growing body of evidence that is reshaping commonly held beliefs about megalodon and its close relatives, said Alberto Collareta, a researcher in the department of Earth sciences at Italy's University of Pisa who was not involved in the research. 'These have led us to abandon traditional reconstruction of the megatooth sharks as 'inflated' versions of the modern white shark. We now know that the Megalodon was something else — in terms of size, shape and ancestry, and of biology, too,' Collareta said via email. 'The Miocene (palaeo)ecosystems in question did not work in a radically different way compared to their modern counterparts — even if they feature … completely extinct protagonists such as the megatooth sharks,' he added, highlighting what he found to be the report's key takeaway. 'That said, it is still useful to acknowledge that our understanding of the Meg is essentially limited to its ubiquitous teeth, a few vertebrae and a handful of scales. What I'd really love to see emerging from 'the foggy ruins of time' is a complete Meg skeleton… Let's hope that the fossil record will amaze us once again.'
Yahoo
27-05-2025
- General
- Yahoo
Analysis of fossil teeth upends what's known about megalodon's diet, scientists say
Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. What scientists understand about the voracious feeding habits of the colossal megalodon could be up for some revision. The prehistoric predator that went extinct about 3.6 million years ago was not hunting only large marine mammals such as whales as researchers widely thought, a new study has found. Instead, minerals in fossilized teeth reveal that megalodon might have been an opportunistic feeder to meet its remarkable 100,000-calorie-per-day requirement. 'When available, it would probably have fed on large prey items, but when not available, it was flexible enough to feed also on smaller animals to fulfill its dietary requirements,' said lead study author Jeremy McCormack, a geoscientist at Goethe University in Frankfurt, Germany. The study, published Monday in the journal Earth and Planetary Science Letters, also showed there were regional differences in the giant shark's feeding habits. The finding suggests megalodon would pursue whatever was in local waters, devouring other top predators and smaller prey alike. 'They were not concentrating on certain prey types, but they must have fed throughout the food web, on many different species,' McCormack said. While certainly this was a fierce apex predator, and no one else would probably prey on an adult megalodon, it's clear that they themselves could potentially feed on almost everything else that swam around.' Megalodon dispatched its prey with a ferocious bite and lethal, serrated teeth that could reach up to 7 inches (18 centimeters) long — the size of a human hand. The superpredator's teeth — abundant in the fossil record — are what McCormack and his colleagues used to conduct a geochemical analysis, unlocking fresh clues that could challenge megalodon's role as sole king of the ancient seas. It's not the first time that a study has challenged previous knowledge about the enormous sea creature. In fact, many questions remain unanswered about Otodus megalodon — its scientific species name meaning 'giant tooth' — since no complete fossil has ever been discovered. The lack of hard evidence stems from the fact that fish skeletons are made of softer cartilage rather than bone, so they don't fossilize very well. Recent research found that the animal was more warm-blooded than other sharks, for example, and there is an ongoing debate about its size and shape. Scientists who created a 3D reconstruction suggested in 2022 that megalodon was about three times as long as a great white shark — about 52 feet (16 meters). However, a March study hypothesized that the megashark was actually much larger — up to 80 feet (24 meters) in length and even longer than the fictional version in the 2018 blockbuster 'The Meg,' which suggested the ancient predator was 75 feet (23 meters) from head to tail. As for megalodon's feeding habits, determining what it ate based on fossil evidence poses challenges, according to McCormack. 'We know that they fed on large marine mammals from tooth bite marks,' he said. 'Of course, you can see bite marks on the bones of marine mammals, but you will not see them if they fed on other sharks, because sharks don't have bones. So there's already a bias in this kind of fossil record.' To glean more about megalodon's prey selection, McCormack and his coauthors looked at the giant shark's fossilized teeth and compared them with those of other animals that lived at the same time, as well as teeth from modern sharks and other predators such as dolphins. The researchers used specimens from museum collections and samples from beached animal carcasses. Specifically, the study team conducted a lab analysis of zinc, a mineral that is acquired only through food. Zinc is essential for living organisms and plays a crucial role in tooth development. The ratio of heavy and light zinc isotopes in the sharks' tooth enamel preserves a record of the kind of animal matter that they ate. Different types, or isotopes, of zinc are absorbed when fish and other animals eat, but one of them — zinc-66 — is stored in tooth enamel much less than another, zinc-64. The ratio between those zinc isotopes widens the further away an animal gets from the lowest level of the food chain. That means that a fish eating other fish would have lower levels of zinc-66 compared with zinc-64, and the fish that eat those fish will have even less zinc-66 compared with zinc-64, creating ratio markers that can help draw up a sequence of the food chain. The researchers found that sea bream, a fish that feeds on mussels and crustaceans, was at the bottom of their reconstructed chain, followed by smaller sharks from the Carcharhinus genus, up to 9.8 feet (3 meters) in length, and extinct toothed whales comparable in size to modern dolphins. Farther up were larger sharks such as the Galeocerdo aduncus, similar to a modern tiger shark, and occupying the top slot was megalodon — but its zinc ratios were not so different as to suggest a massive gap with the lower-tier animals, meaning they might have been part of megalodon's diet, too. 'Based on our new results, we see that it was clear it could feed at the very top, but it was flexible enough to feed also on lower (levels of the food chain),' McCormack said. In addition, the researchers found megalodon was not alone at the top of the food chain but instead shared the spot with other 'opportunistic supercarnivores' such as its close relative Otodus chubutensis and the lesser-known Araloselachus cuspidatus, another giant fish-eating shark. That revelation challenges the assumption that megalodon was the exclusive ruler of the oceans and draws comparisons with the great white shark, another large opportunistic feeder. The finding also reinforces the idea that the rise of the great white may have been a factor in megalodon's extinction, according to paleobiologist Kenshu Shimada, one of the coauthors of the latest study. 'One of the contributing factors for the demise of megalodon has been hypothesized to be the rise of the great white shark, which feeds on fish when young and shifts its diet to marine mammals as it becomes larger,' said Shimada, a professor of biological and environmental sciences at DePaul University in Chicago. 'Our new study, that demonstrates the 'diet overlap' between the great white shark and megalodon, strengthens the idea that the evolution of the smaller, likely more agile and maneuverable great white shark could have indeed (driven) megalodon to extinction.' The new research allows scientists to recreate a snapshot of the marine food web that existed about 20 million years ago, according to Jack Cooper, a UK-based paleobiologist and megalodon expert who wasn't involved with the study. 'The general picture of megalodon has been of a gigantic shark munching on whales,' Cooper said in an email. 'This study adds a new dimension that megalodon probably had a wide range of prey — essentially, it probably ate not just whales but whatever it wanted.' Another interesting find, he added, is that megalodon's diet probably varied slightly between different populations, something observed in today's great white sharks. 'This makes sense and is something we would have probably expected since megalodon lived all over the world and not all of its prey items would have done; but it's wonderful to have concrete data supporting this hypothesis,' Cooper said. The study adds to a growing body of evidence that is reshaping commonly held beliefs about megalodon and its close relatives, said Alberto Collareta, a researcher in the department of Earth sciences at Italy's University of Pisa who was not involved in the research. 'These have led us to abandon traditional reconstruction of the megatooth sharks as 'inflated' versions of the modern white shark. We now know that the Megalodon was something else — in terms of size, shape and ancestry, and of biology, too,' Collareta said via email. 'The Miocene (palaeo)ecosystems in question did not work in a radically different way compared to their modern counterparts — even if they feature … completely extinct protagonists such as the megatooth sharks,' he added, highlighting what he found to be the report's key takeaway. 'That said, it is still useful to acknowledge that our understanding of the Meg is essentially limited to its ubiquitous teeth, a few vertebrae and a handful of scales. What I'd really love to see emerging from 'the foggy ruins of time' is a complete Meg skeleton… Let's hope that the fossil record will amaze us once again.'
CNN
27-05-2025
- General
- CNN
Fossil teeth analysis upends what's known about megalodon's diet, scientists say
What scientists understand about the voracious feeding habits of the colossal megalodon could be up for some revision. The prehistoric predator that went extinct about 3.6 million years ago was not hunting only large marine mammals such as whales as researchers widely thought, a new study has found. Instead, minerals in fossilized teeth reveal that megalodon might have been an opportunistic feeder to meet its remarkable 100,000-calorie-per-day requirement. 'When available, it would probably have fed on large prey items, but when not available, it was flexible enough to feed also on smaller animals to fulfill its dietary requirements,' said lead study author Jeremy McCormack, a geoscientist at Goethe University in Frankfurt, Germany. The study, published Monday in the journal Earth and Planetary Science Letters, also showed there were regional differences in the giant shark's feeding habits. The finding suggests megalodon would pursue whatever was in local waters, devouring other top predators and smaller prey alike. 'They were not concentrating on certain prey types, but they must have fed throughout the food web, on many different species,' McCormack said. While certainly this was a fierce apex predator, and no one else would probably prey on an adult megalodon, it's clear that they themselves could potentially feed on almost everything else that swam around.' Megalodon dispatched its prey with a ferocious bite and lethal, serrated teeth that could reach up to 7 inches (18 centimeters) long — the size of a human hand. The superpredator's teeth — abundant in the fossil record — are what McCormack and his colleagues used to conduct a geochemical analysis, unlocking fresh clues that could challenge megalodon's role as sole king of the ancient seas. It's not the first time that a study has challenged previous knowledge about the enormous sea creature. In fact, many questions remain unanswered about Otodus megalodon — its scientific species name meaning 'giant tooth' — since no complete fossil has ever been discovered. The lack of hard evidence stems from the fact that fish skeletons are made of softer cartilage rather than bone, so they don't fossilize very well. Recent research found that the animal was more warm-blooded than other sharks, for example, and there is an ongoing debate about its size and shape. Scientists who created a 3D reconstruction suggested in 2022 that megalodon was about three times as long as a great white shark — about 52 feet (16 meters). However, a March study hypothesized that the megashark was actually much larger — up to 80 feet (24 meters) in length and even longer than the fictional version in the 2018 blockbuster 'The Meg,' which suggested the ancient predator was 75 feet (23 meters) from head to tail. As for megalodon's feeding habits, determining what it ate based on fossil evidence poses challenges, according to McCormack. 'We know that they fed on large marine mammals from tooth bite marks,' he said. 'Of course, you can see bite marks on the bones of marine mammals, but you will not see them if they fed on other sharks, because sharks don't have bones. So there's already a bias in this kind of fossil record.' To glean more about megalodon's prey selection, McCormack and his coauthors looked at the giant shark's fossilized teeth and compared them with those of other animals that lived at the same time, as well as teeth from modern sharks and other predators such as dolphins. The researchers used specimens from museum collections and samples from beached animal carcasses. Specifically, the study team conducted a lab analysis of zinc, a mineral that is acquired only through food. Zinc is essential for living organisms and plays a crucial role in tooth development. The ratio of heavy and light zinc isotopes in the sharks' tooth enamel preserves a record of the kind of animal matter that they ate. Different types, or isotopes, of zinc are absorbed when fish and other animals eat, but one of them — zinc-66 — is stored in tooth enamel much less than another, zinc-64. The ratio between those zinc isotopes widens the further away an animal gets from the lowest level of the food chain. That means that a fish eating other fish would have lower levels of zinc-66 compared with zinc-64, and the fish that eat those fish will have even less zinc-66 compared with zinc-64, creating ratio markers that can help draw up a sequence of the food chain. The researchers found that sea bream, a fish that feeds on mussels and crustaceans, was at the bottom of their reconstructed chain, followed by smaller sharks from the Carcharhinus genus, up to 9.8 feet (3 meters) in length, and extinct toothed whales comparable in size to modern dolphins. Farther up were larger sharks such as the Galeocerdo aduncus, similar to a modern tiger shark, and occupying the top slot was megalodon — but its zinc ratios were not so different as to suggest a massive gap with the lower-tier animals, meaning they might have been part of megalodon's diet, too. 'Based on our new results, we see that it was clear it could feed at the very top, but it was flexible enough to feed also on lower (levels of the food chain),' McCormack said. In addition, the researchers found megalodon was not alone at the top of the food chain but instead shared the spot with other 'opportunistic supercarnivores' such as its close relative Otodus chubutensis and the lesser-known Araloselachus cuspidatus, another giant fish-eating shark. That revelation challenges the assumption that megalodon was the exclusive ruler of the oceans and draws comparisons with the great white shark, another large opportunistic feeder. The finding also reinforces the idea that the rise of the great white may have been a factor in megalodon's extinction, according to paleobiologist Kenshu Shimada, one of the coauthors of the latest study. 'One of the contributing factors for the demise of megalodon has been hypothesized to be the rise of the great white shark, which feeds on fish when young and shifts its diet to marine mammals as it becomes larger,' said Shimada, a professor of biological and environmental sciences at DePaul University in Chicago. 'Our new study, that demonstrates the 'diet overlap' between the great white shark and megalodon, strengthens the idea that the evolution of the smaller, likely more agile and maneuverable great white shark could have indeed (driven) megalodon to extinction.' The new research allows scientists to recreate a snapshot of the marine food web that existed about 20 million years ago, according to Jack Cooper, a UK-based paleobiologist and megalodon expert who wasn't involved with the study. 'The general picture of megalodon has been of a gigantic shark munching on whales,' Cooper said in an email. 'This study adds a new dimension that megalodon probably had a wide range of prey — essentially, it probably ate not just whales but whatever it wanted.' Another interesting find, he added, is that megalodon's diet probably varied slightly between different populations, something observed in today's great white sharks. 'This makes sense and is something we would have probably expected since megalodon lived all over the world and not all of its prey items would have done; but it's wonderful to have concrete data supporting this hypothesis,' Cooper said. The study adds to a growing body of evidence that is reshaping commonly held beliefs about megalodon and its close relatives, said Alberto Collareta, a researcher in the department of Earth sciences at Italy's University of Pisa who was not involved in the research. 'These have led us to abandon traditional reconstruction of the megatooth sharks as 'inflated' versions of the modern white shark. We now know that the Megalodon was something else — in terms of size, shape and ancestry, and of biology, too,' Collareta said via email. 'The Miocene (palaeo)ecosystems in question did not work in a radically different way compared to their modern counterparts — even if they feature … completely extinct protagonists such as the megatooth sharks,' he added, highlighting what he found to be the report's key takeaway. 'That said, it is still useful to acknowledge that our understanding of the Meg is essentially limited to its ubiquitous teeth, a few vertebrae and a handful of scales. What I'd really love to see emerging from 'the foggy ruins of time' is a complete Meg skeleton… Let's hope that the fossil record will amaze us once again.'
Forbes
26-05-2025
- Science
- Forbes
Largest Shark To Ever Swim In Our Oceans Was Not A Picky Eater
Fossil O. megalodon tooth compared to a recent-day great white shark tooth. Otodus megalodon, the largest shark to ever swim in our planet's oceans, still inhabited the sea up to around 3.6 million years ago. Despite its fame in pop-culture, surprisingly little is known about the anatomy and behavior of this species. Sharks have only a cartilaginous skeleton that quickly decays after death, only their hard teeth survive the long and arduous fossilization process. Based on the fragmentary remains, length estimates for a full-grown O. megalodon range from 50 to 100 feet (15-30 meters). Special evolutionary adaptions including warm-bloodedness (an organism's ability to maintain a relatively constant internal temperature) and giving birth to fully-developed newborns likely led to this gigantism. The living animal required around 100,000 kilocalories per day. Scientists widely assumed that O. megalodon's main calorie intake was in the form of whales, large preys providing also a high-caloric input thanks to their fat reserves. However O. megalodon was not a picky eater, says Dr. Jeremy McCormack from the Department of Geosciences at Goethe University Frankfurt. McCormack and colleagues extracted zinc from the fossil teeth, an element that occurs in isotopes of different weights. Zinc is ingested with food, but the specific isotopes preserved in muscles, organs and skeletal tissues depend on the animal's place in the food chain. The tissue of large fish that eat smaller fish absorbs significantly less zinc-66, and predatory animal which, in turn, hunt them for food absorb even less. "Since we don't know how the ratio of the two zinc isotopes at the bottom of the food pyramid was at that time, we compared the teeth of various prehistoric and extant shark species with each other and with other animal species. This enabled us to gain an impression of predator-prey relationships," explains McCormack. The fossils they used for their study mostly came from marine deposits in Sigmaringen and Passau (Germany). Analyzing the zinc isotopes in the fossil remains of different species, they reconstructed the food chain as it appeared 18 million years ago. "Sea bream, which fed on mussels, snails and crustaceans, formed the lowest level of the food chain we studied. Smaller shark species such as requiem sharks and ancestors of today's cetaceans, dolphins and whales, were next. Larger sharks such as sand tiger sharks were further up the food pyramid, and at the top were giant sharks like Araloselachus cuspidatus and the Otodus sharks, which include megalodon," explains McCormack. The zinc signal in fossil O. megalodon teeth is more variable than expected. 'Our study tends rather to draw a picture of megalodon as an ecologically versatile generalist; … by all means flexible enough to feed on marine mammals and large fish, from the top of the food pyramid as well as lower levels — depending on availability.' "It gives us important insights into how the marine communities have changed over geologic time, but more importantly the fact that even 'supercarnivores' are not immune to extinction," adds Kenshu Shimada, a paleobiologist at DePaul University in Chicago, U.S., and a coauthor of the new study. The study,"Miocene marine vertebrate trophic ecology reveals megatooth sharks as opportunistic supercarnivores," was published in the journal Earth and Planetary Science Letters. Additional material and interviews provided by Sadie Harley and Robert Egan, Goethe University Frankfurt am Main.
Yahoo
26-05-2025
- Science
- Yahoo
Giant Megalodon's Prey Finally Revealed, And It's Not What We Thought
Megalodon, the terror of the Neogene, dominated its giant shark niche for just 20 million years before it disappeared from the world's oceans. And, during that time, it hunted anything and everything that crossed its path. It didn't distinguish: if it was large enough to be a snack, megalodon (Odontus megalodon) partook. Scientists have reached that conclusion after studying the teeth of modern sharks, and comparing them to the fossilized teeth of megalodon, almost all we have left of the extinct fish today. This contradicts the theory that the main prey of megalodon was whales. Certainly megalodon could and did eat whales – but its diet as a whole was far more opportunistic. "Our study tends rather to draw a picture of megalodon as an ecologically versatile generalist," says geoscientist Jeremy McCormack of Goethe University Frankfurt in Germany "Megalodon was by all means flexible enough to feed on marine mammals and large fish, from the top of the food pyramid as well as lower levels – depending on availability." Megalodon is an extinct species of shark that lived from around 23 million to around 3.6 million years ago, during which time it occupied a prime position at the top of the food web, before being driven to extinction. We will never know for certain what it looked like; like all sharks, its skeleton was mostly cartilage, and all it left behind was a lot of teeth and a few vertebrae. We know from these remains, however, that megalodon was enormous, with size estimates ranging from around 11 meters to over 40 meters (36 to 131 feet) in length (although the latter is an outlier, and most estimates hover around 13 to 20 meters). That's huge – so huge that scientists think that megalodon may have specialized in large prey. One way to determine the diet of someone who has been dead a long time is to look at isotopes in their teeth. An isotope of an element is an atom that deviates from the norm in the number of neutrons it has in its nucleus, and the ratios of these isotopes vary according to several factors, one of which is diet. This is because when we eat, some of the metals in our food replace some of the calcium in our teeth and bones – not so you notice, obviously, but enough to leave a tracer. McCormack and his colleagues looked specifically at the ratios of two isotopes of zinc – the lighter zinc-64 and the heavier zinc-66. When fish at the bottom of the food web eat, they store less zinc-66 than zinc-64. The fish that eat those fish have even less zinc-66. So when you get to the fish at the very top of the chain, you see the very least zinc-66 compared to zinc-64. This is what the researchers observed in the teeth of megalodon and its cousin, the extinct Odontus chubutensis. The researchers don't really know what was at the bottom of the food chain 18 million years ago, the time from which the megalodon teeth they studied hailed. So, they compared the megalodon teeth with the teeth of sharks that swim the oceans today to work out what the giant predators ate. "Sea bream, which fed on mussels, snails, and crustaceans, formed the lowest level of the food chain we studied," McCormack says. "Smaller shark species such as requiem sharks and ancestors of today's cetaceans, dolphins, and whales, were next. Larger sharks such as sand tiger sharks were further up the food pyramid, and at the top were giant sharks like Araloselachus cuspidatus and the Otodus sharks, which include megalodon." Megalodon's status as a superpredator at the very top of the food web has been established previously. The new research reveals that the isotope difference between megalodon and the animals at the lowest level the researchers studied was not a sharp delineation, suggesting that the shark was not a fussy eater. There were also intriguing differences in megalodon diet depending on where the animals lived. Megalodon teeth found in Passau, Germany, dined more heavily on the lower levels of the food web, the researchers found. This is not dissimilar to the opportunistic hunting approach demonstrated by white sharks (Carcharias carcharodon), which stands to reason: previous work led by McCormack showed that the rise of the white shark was likely one of the drivers that led megalodon to extinction. With competition in its ecological niche, megalodon became more vulnerable. "It gives us important insights into how the marine communities have changed over geologic time," says paleobiologist Kenshu Shimada of DePaul University in the US, "but more importantly the fact that even 'supercarnivores' are not immune to extinction." The research has been published in Earth and Planetary Science Letters. Earth's Core Holds a Vast Reservoir of Gold, And It's Leaking Toward The Surface Scientists Peered Inside The Echidna's Mysterious 'Pseudo-Pouch' Bizarre Three-Eyed Predator Hunted The Ocean Half a Billion Years Ago
