Ancient sharks bit plesiosaur


Fossil shark feeding frenzy

From National Geographic:

“Sea Monster” Bones Reveal Ancient Shark Feeding Frenzy

Matt Kaplan
for National Geographic News

September 28, 2009

A gang of ancient sharks took on an enormous “sea monster” 85 million years ago, according to a new fossil analysis.

The bones of the prehistoric reptile, known as a plesiosaur, were found in Japan in 1968. But a lack of comparative samples and other resources meant that scientists didn’t release a formal description of the fossil until recently.

“As a child in Japan, I had heard that there were some shark teeth embedded in the plesiosaur,” recalled Kenshu Shimada, a paleontologist at DePaul University in Chicago.

“But the [new] description revealed over 80. That is a lot of teeth to have in a fossil,” he said.

After reading the report, Shimada wanted to take a closer look at the types of shark teeth. Based on his findings, he estimates that at least seven sharks of different ages attacked the plesiosaur.

The scientist was even more shocked when he identified the species of attacking shark: the extinct, nine-foot-long (three-meter-long) Cretalamna appendiculata.

By contrast, the sharks’ plesiosaur prey was a roughly 23-foot-long (7-meter-long) animal armed with a mouth full of razor-sharp teeth and powerfully muscled, paddlelike limbs.

Feeding Frenzy

Sharks regularly lose some of their many teeth whenever they bite prey. These teeth fall out and are regrown throughout their lives.

Shimada and colleagues found that the teeth they removed from the plesiosaur were from the same species but of different sizes and shapes.

This suggests there was a multigenerational feeding frenzy, said Jürgen Kriwet, a paleontologist at the State Museum of Natural History in Stuttgart, Germany.

Among modern-day great white sharks, for instance, juveniles will ravenously bite prey in a group but flee as soon as larger adult sharks arrive, said Kriwet, who was not involved in the new research.

A similar event may have taken place when the ancient sharks attacked, he said.

(See shark pictures submitted by National Geographic readers.)

Wounded Prey

Harder to determine is whether the sharks went after a live, wounded, or dead plesiosaur.

(Related: “Giant ‘Sea Monster’ Fossil Discovered in Arctic.”)

“In the modern day, we usually see sharks of this size scavenging on animals larger than themselves,” Kriwet said.

“And if they do attack, they are often attacking large animals that are already wounded.”

DePaul University’s Shimada said he thinks the plesiosaur was dead or nearly so.

“A healthy plesiosaur,” he said, “would have badly beat up these sharks.”

Findings reported last week at the annual meeting of the Society of Vertebrate Paleontology in Bristol, England,

Tags reveal white sharks have neighbourhoods in the north Pacific, say Stanford researchers: here.

Brown shyshark (Haploblepharus fuscus): here.

7 thoughts on “Ancient sharks bit plesiosaur

  1. Dead whales may be luring huge shark

    26th October 2009

    AAP

    WHALE carcasses left to rot in southeast Queensland’s Moreton Bay could be attracting a monster shark believed to be lurking in the area.

    A three-metre plus white pointer caught on drum line off Stradbroke Island was found dead and covered in massive bite marks last week.

    Queensland Fisheries Minister Tim Mulherin said the bite marks had a radius of 50cm and the distinctive triangular shape of a white pointer.

    “The experts believe it would have taken a white pointer at least five metres long to cause this kind of damage,” Mr Mulherin said.

    Wildlife Preservation Society of Queensland president Simon Baltais said the dumping of whale carcasses in the area was providing a huge meat tray for such big predators.

    Three whales that died in southeast Queensland waters in recent months had been towed to Mud Island in Moreton Bay.

    “The whale carcasses are taken up the shoreline (of Mud Island) and rot away…,” Mr Baltais said.

    “It would certainly attract a lot of predators and scavengers – white pointers love dead whales.”

    He said the carcasses should be towed out to sea away from populated beaches and bays.

    “It is costly but is the lost of one human worth it because it was too costly to tow carcasses further out?” Mr Baltais said.

    Mr Mulherin said the discovery re-enforced the importance of shark nets and drum lines.

    “People have forgotten why Queensland, New South Wales, and South Africa introduced nets in the first place,” he said.

    “During one horrific period in South Africa in the late 1950s five people were killed in three and a half months.”

    He said Queensland had five fatal shark attacks between 1958 and 1961 but since the shark control program was introduced in 1962, there has only been one fatal attack on a protected beach.

    Some critics say nets should be removed during the whale migration season with five whales becoming entangled so far this year.

    Sea World’s director of marine sciences, Trevor Long, told AAP last month that sharks could easily swim around the nets that are 600 metres long and five metres deep and only protect 11 out of 27 Gold Coast beaches.

    http://www.sunshinecoastdaily.com.au/story/2009/10/26/dead-whales-may-be-luring-monster-shark/

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