Great white shark, megalodon, and evolution

From ScienceDaily:

Preserved Shark Fossil Adds Evidence To Great White‘s Origins

(Mar. 13, 2009) — A new University of Florida study could help resolve a long-standing debate in shark paleontology: From which line of species did the modern great white shark evolve?

For the last 150 years, some paleontologists have concluded the great white shark, Carcharodon carcharias, is a smaller relative of the line that produced Carcharodon megalodon, the largest carnivorous fish known. Other paleontologists disagree, arguing the great white shark evolved instead from the broad-toothed mako shark. The second group contends megalodon, which grew to a length of 60 feet, should have its genus name switched to Carcharocles to reflect its different ancestry.

Megalodon and great white shark

The study in the March 12 issue of the Journal of Vertebrate Paleontology falls squarely into the mako camp. It concludes megalodon and modern white sharks are much more distantly related than paleontologists initially believed.

“I think that this specimen will clarify things,” said lead author Dana Ehret, a vertebrate paleontology graduate student at the Florida Museum of Natural History located on the UF campus. “When we only have isolated teeth to describe, it’s very hard to come to a definitive conclusion.”

The study is based on a remarkably well preserved 4- to 5-million-year-old fossil from Peru of an early white shark species: a complete jaw with 222 teeth intact and 45 vertebrae. Most ancient shark species are known only from isolated teeth. Based on tooth size and analysis of growth rings within the vertebrae, the shark was about 20 years old and 17 to 18 feet long, a size in the range of modern white sharks.

Having the teeth in place allows researchers to see important distinguishing characteristics that help determine a fossil’s genus and species, such as whether a tooth curves toward the outside of the jaw or its midline, Ehret said. He believes the fossil belongs to a white shark species closely related to Isurus hastalis, a broad-toothed mako shark that probably grew to 27 feet long and lived 9 million to 10 million years ago.

An olive-grove farmer trained in fossil collection discovered it near his home in the desert of southern Peru in 1988. It now belongs to a private collection and was only recently pledged to the Florida Museum of Natural History. …

The specimen came from an area known as the Pisco Formation, famous for its rich fossil beds dating from the late Miocene to Pleistocene, about 1 million to 9 million years ago. The region was once a sheltered, shallow marine environment ideal for preserving skeletons. The formation has produced articulated broad-toothed mako shark skeletons as well as fossils of whales, aquatic sloths and sea turtles.

The study strengthens the evolutionary link between the extinct mako and the modern white shark, said vertebrate paleontologist Kenshu Shimada, an associate professor at DePaul University in Chicago. Shimada said paleontologists now need fossil skeletons from megalodon and a shark from the extinct Otodontidae family such as Otodus, a large prehistoric mackerel shark that lived about 40 million to 60 million years ago.

“If we can demonstrate the strong link between Carcharocles and Otodus from such skeletal remains,” Shimada said, “we may be able to settle the evolutionary and taxonomic debates.”

Megalodon was first classified in the same genus as the modern white shark in the 1840s based on the similarity of tooth shape and serrations specialized for eating marine mammals. Mako sharks have no serrations because they feed primarily on fish.

Ehret says the shark fossil’s coarse serrations are evidence of a transition between broad-toothed mako sharks and modern white sharks.

“Here we have a shark that’s gaining serrations,” he said. “It’s becoming a white shark, but it’s not quite there yet.”

The transition from megatooth sharks like megalodon to modern white sharks would require changes in body size and tooth serrations, thickness and enamel, Ehret said. By contrast, the transition from the broad-toothed mako shark to modern white sharks would require only the presence of serrations and a shift in the slant of a key tooth position.

Did Discovery Channel fake the image in its giant shark documentary? Image showing Megalodon swimming past U-boats off Cape Town was doctored. Come clean, or prove me wrong: here.

Economic Recession Means Fewer Shark Attacks: here.

Vast Bed of Ancient Bones and Shark Teeth Explained: here.

33,000 sharks, 2000 dolphins & 2000 turtles killed to boost beach tourism in South Africa: here.

Great whites ‘plan’ seal attacks: here.

Largest prehistoric Megalodon shark jaw ever assembled up for auction: here.

The larg­est known shark species ev­er, Car­charo­cles mega­lodon, reached lengths up to 18 me­ters (59 feet). That’s the length of a vol­ley­ball court, or about three times that of a typ­i­cal adult great white. (The fic­tion­al “Jaws” was por­trayed as 25 feet long). But the an­cient beast, thought to have fed on ma­rine mam­mals dur­ing its ter­ri­fy­ing ex­ist­ence be­tween 23 mil­lion and 2.6 mil­lion years ago, died out. Sci­en­tists have blamed cli­mate changes for the dis­ap­pear­ance, but a new study con­cludes that the shark per­ished be­cause the di­vers­ity of its prey shrank and new com­peti­tors ap­peared.

For years, paleontologists speculated why the famous 18 meter (59 foot) long shark disappeared from the oceans around 2.6 million years ago. New evidence suggests competition and lack of food may have been the causes: here.

28 thoughts on “Great white shark, megalodon, and evolution

  1. Helen Bamford

    March 15 2009 at 02:40PM

    * Skipper ‘gave false information’

    A Taiwanese fishing vessel with nearly two tons of dried shark fins on board was seized at Cape Town harbour on Saturday.

    The fins were confiscated by Department of Environmental Affairs inspectors and the skipper and crew of 26 face criminal charges for providing false information about their catch.

    Carol Moses, spokesperson for Marine and Coastal Management (MCM), said it was clear the foreign-flagged vessel, the Chien Jui 102, had been finning. This practice involves hacking fins off live sharks and throwing them back into the sea where they either bleed to death or become prey for other sharks.

    The organisation World Conservation estimates that finning causes the death of tens of millions of sharks worldwide each year.

    The demand for shark fins is mostly to supply the East with shark fin soup, where it is regarded as a delicacy. Blacktip, silky and blue sharks are among those targeted.

    Moses said that in terms of international regulations, the number of shark fins landed must correspond with the number of shark trunks on board.

    She said that both the Indian Ocean Tuna Commission and the International Commission for the Conservation of Atlantic Tunas prescribed that the weight of the fins should not be more than 5% of the shark trunk.

    Moses said the Chien Jui 102’s permit had indicated they had 100kg of shark fin, 2,2 tons of shark trunk and 2 945kg of tuna on board.

    But what they, in fact, had was nearly two tons of dried shark fins, which meant they should have had about 30 tons of shark trunk.

    Moses said the vessel would be blacklisted for illegal, unreported and unregulated fishing and would remain in the harbour until the case had been finalised.

    She said the Marine Living Resources Act made provision for a fine of up to R2 million and up to five years’ imprisonment. She said the charges were still being formulated.

    Moses said the vessel had been at sea since December, fishing off-shore on the high seas but had applied for an exclusive economic zone permit to enter South African waters.

    “If they want to come into our waters to offload or do repairs they have to apply for a permit and provide details of their catch and the type of fishing gear they have on board.”

    The vessel was granted a permit on March 4 and two days later MCM inspectors boarded it at the harbour to do a spot check.

    She said that should the skipper and crew be found guilty, MCM would sell the fish and the proceeds would go into the Marine Living Resources fund.
    o This article was originally published on page 3 of Cape Argus on March 15, 2009


  2. Scientists fear boneyard sale will stop research

    By TRACIE CONE, Associated Press Writer

    Friday, June 12, 2009

    (06-12) 12:56 PDT Bakersfield, Calif. (AP) —

    Last week, scientists said they solved an enduring mystery about the origins of a prehistoric boneyard of gigantic marine creatures in the desolate desert here.

    But another mystery has arisen: Will the looming sale of the land mean the end of research into the one of the largest finds of mid-Miocene fossils?

    “There is so much we still need to learn about how all of these things fit into the overall evolutionary history,” said Jere H. Lipps, a UC Berkeley evolutionary biologist who has been studying this ancient seabed since he was a UCLA student 50 years ago.

    Two years ago, Robert Ernst, the amateur paleontologist who owned the property, died unexpectedly and without a will.

    Since then his widow, Mary, 53, has suffered through heartache, probate and a back injury, which is forcing her early retirement next month from the Bakersfield Parks and Recreation Department. She said she is selling the site on Sharktooth Hill to pay her husband’s loans, taxes and legal fees.

    “To the right person, it could really be special. Like it was to Bob,” said Ernst, who with her attorney, Stephen Boyle, sent out 35 prospectuses to potential buyers, including some of the nation’s top paleontology museums.

    They decline to say how much they are seeking for the 342-acre site, appraised at roughly $132,000 as marginal grazing land. The land — which has yielded priceless intact specimens, such as the ancient sea lion Allodesmus — is slated to go July 17 to the highest bidder.

    “How do you assign a value to that?” Doyle asked. “Is there another one out there?”

    The parched hills east of Bakersfield, better known for the oil rigs that pump crude from even deeper ancient seabed, were part of a tropical oasis 15 million years ago.

    Extinct species of manatees munched on marsh grasses, elephant-like gomphotheres roamed the shore beside pre-evolutionary horses, and 70-foot Megalodon sharks with seven-inch teeth ripped into a teeming seafood buffet that included sea lions and sea turtles the size of minivans.

    The place should be a park on the order of Dinosaur National Monument, say paleontologists, who have catalogued 125 one-of-a-kind species during more than 80 years of unfettered access.

    But the reality in a cash-strapped state, experts say, is that skeletons worth potentially millions of dollars make the land more valuable to private collectors and well-endowed museums.

    Lipps was part of a team that announced June 6 it had solved the mystery that has puzzled scientists since the site was discovered by railroad surveyors 150 years ago. Why did boundless bones mixed with shark teeth accumulate so heavily here? The prevailing thought was that everything died at once in a volcanic eruption or some other cataclysmic event.

    But Lipps’ team studied the layers of bones to conclude the opposite: That the animals died over a period of 700,000 years, and rising sea levels kept silt from covering them.

    Over the years, people have removed countless fossils. Some went to the California Academy of Sciences in San Francisco and the Museum of Paleontology at UC Berkeley, but others were taken by thieves who ignored the law against taking fossils from private land.

    The most famous skeleton found there — the only fully articulated Allodesmus sea lion in the world — is displayed in a glass case at the Buena Vista Natural History Museum, which occupies the old JC Penney building in downtown Bakersfield. Ernst founded the museum in 1984 to house his fossil collection, which his widow now owns and was recently appraised for about $600,000.

    “These are all part of Kern County’s history,” said the museum’s part-time executive director, Koral Hancharick.

    Mary Ernst says she does not know whether she will sell any of the museum collection, but she wants to sell Sharktooth Hill.

    This week she ventured the site to show off her husband’s last find — a baby baleen whale that his meticulous work had left half revealed. She bounced her Jeep along unpaved roads and through locked gates to the sun-baked spot. She froze as she realized the baby baleen was gone — stolen — a half dozen plastic water bottles left in its place.

    “Where is she?” Mary Ernst said, kicking at the dirt, then sighing. “They could have at least taken their litter.”


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    New ancient shark species gives insight into origin of great white

    GAINESVILLE, Fla. — The great white shark is one of the largest living predatory animals and a magnet for media sensationalism, yet its evolutionary history is as misunderstood as its role as a menace.

    Originally classified as a direct relative of megatooth sharks, the white shark’s evolutionary history has been debated by paleontologists for the last 150 years. In a study appearing in print and online today in the journal Palaeontology, University of Florida researchers name and describe an ancient intermediate form of the white shark, Carcharodon hubbelli, which shows the modern white shark likely descended from broad-toothed mako sharks. The study deviates from the white shark’s original classification as a relative of megatooth sharks such as the extinct Carcharocles megalodon, the largest carnivorous shark that ever lived.

    Based on recalibrated dates of the excavation site in Peru, the study also concludes the new species was about 2 million years older than previously believed.

    “We can look at white sharks today a little bit differently ecologically if we know that they come from a mako shark ancestor,” said lead author Dana Ehret, a lecturer at Monmouth University in New Jersey who conducted research for the study as a UF graduate student. “That 2-million-year pushback is pretty significant because in the evolutionary history of white sharks, that puts this species in a more appropriate time category to be ancestral or kind of an intermediate form of white shark.”

    Most ancient shark species are named using isolated teeth, but analysis of C. hubbelli, also known as Hubbell’s white shark, was based on a complete set of jaws with 222 teeth intact and 45 vertebrae. The species was named for Gainesville resident Gordon Hubbell, a collector who recovered the fossils from a farmer who discovered them in the Pisco Formation of southern Peru in 1988. Hubbell donated the specimens to the Florida Museum of Natural History on the UF campus in December 2009.

    “The impetus of this project was really the fact that Gordon Hubbell donated a majority of his fossil shark collection to the Florida Museum,” Ehret said. “Naming the shark in his honor is a small tip of the hat to all the great things he has done to advance paleontology.”

    Ehret and co-authors published an initial study describing the shark specimens in the Journal of Vertebrate Paleontology in 2009, but dates for the site reflected information from a 1985 study about the Pisco Formation, he said. With Hubbell’s hand-drawn maps and descriptions of the landscape, researchers returned to the site and found the exact spot the fossils were discovered.

    Scientists extracted more accurate age estimates from mollusk shells in the fossil horizon to determine the shark species was from the late Miocene, about 6.5 million years ago, rather than the early Pliocene, about 4.5 million years ago. The new dates will also be useful for better understanding other fossils found in the rich Pisco Formation, which include new whale, marine sloth and terrestrial vertebrate species.

    “The thing that was remarkable to me was that these fossils came from right out in the desert and this was before GPS, so Dana had only an approximate notion of where it was,” said Florida Museum of Natural History Director Douglas Jones, a study co-author who conducted strontium isotope dating of the fossils. “But after a few days of looking, we were able to find this deposit and Dana found the rest of the missing shark’s teeth.”

    Researchers determined Hubbell’s white shark was related to ancient broad-toothed mako sharks by comparing the physical shapes of shark teeth to one another. While modern white sharks have serrations on their teeth for consuming marine mammals, mako sharks do not have serrations because they primarily feed on fish. Hubbell’s white shark has coarse serrations indicative of a transition from broad-toothed mako sharks to modern white sharks.

    These evolutionary relationships have been hypothesized for decades, and researchers who interpret modern white sharks as being more closely related to megatooth sharks say it is “a friendly disagreement,” according to Michael Gottfried, an associate professor in geological sciences at Michigan State University.

    But shark expert David Ward, a research associate at the Natural History Museum, London, said “fewer people believe the big megatooth sharks are related to the great white sharks than believe the Earth is flat.”

    “Everyone working within the field will be absolutely delighted to see this relationship formalized,” Ward said.


    Study co-authors include Bruce MacFadden of the Florida Museum, Thomas DeVries of the Burke Museum of Natural History and Culture in Seattle, David Foster of UF and Rodolfo Salas-Gismondi of Museo de Historia Natural Javier Prado in Lima.


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