Giant filter-feeding fish of the dinosaur age


This video is called Walking with…Sharks (including about Leedsichthys).

By Jennifer Viegas:

SUV-Sized Fish Were Earliest Filter-Feeders

Giant whales are known for their open-mouthed filter feeding, but the technique was likely devised by humongous fish that lived during the Mesozoic.

Thu Feb 18, 2010 02:00 PM ET

THE GIST:

* Gigantic filter-feeding fishes lived during the Mesozoic Era.
* Filter feeding didn’t first emerge in whales, as had been previously suspected, but instead began with the now-extinct fishes.
* After the filter-feeding fishes died out with the dinosaurs, whales and other cetaceans filled the ecological niche.

Whales include the world’s largest animals, but newly identified fossils reveal they were preceded by SUV-sized filter-feeding fishes that emerged during the Jurassic Period, 170 million years ago, and lived until the extinction event that wiped out dinosaurs and numerous other species.

Although the now-extinct fishes, called pachycormiforms, were not closely related to whales, their demise left an ecological niche void that whales, sharks and rays filled starting around 56 million years ago, helping to explain the top portion of today’s marine food chain.

The fish fossils, described in the latest issue of Science, also prove that filter feeding emerged long before the first whales. For this method of eating, the diner suspends itself in the water, mouth agape. Water escapes through gill slits, leaving behind the filtered food.

It can help to have a big mouth, which many of these enormous fishes must have had.

Co-author Kenshu Shimada, a research associate in paleontology at the Sternberg Museum of Natural History, told Discovery News that one of the fish he and his colleagues identified, Bonnerichthys, grew to around 20 feet in length and swam through a seaway covering what is today the state of Kansas.

“A previously described species, Leedsichthys, from the Jurassic of Europe that belongs to the same lineage that includes Bonnerichthys was even larger, likely reaching up to about 30 feet, which is the most massive bony fish of all time,” added Shimada, who is also an associate professor in the Environmental Science Program and Department of Biological Sciences at DePaul University.

For the study, led by University of Oxford scientist Matt Friedman, the researchers analyzed both old and new fish fossils found in England, the U.S. and Japan. The Kansas fish was previously thought to have been like a gigantic swordfish, bearing fang-like teeth on its jawbones.

“However, our close examination of the specimen showed that such a long snout and fang-like teeth were not present in the fish,” Shimada said. “Rather, with a blunt massive head, the fish had long toothless jawbones and long gill-supporting bones that are characteristic of plankton-feeding fishes.”

While this fish, and the other Dinosaur-Era filter feeders, enjoyed a long existence on the planet, they were no match for the K-T extinction event that killed off 70 percent of all species then living on Earth.

“The filter-feeding pachycormiforms, relying for food on small organisms low in the trophic chain, had the perfect profile of a victim and became extinct,” wrote Lionel Cavin in a commentary that also appears in Science. Cavin is a curator in the Department of Geology and Paleontology at the Natural History Museum in Geneva.

Cavin added, “The tropical niche was later refilled, first with sharks and rays from around 56 million years ago and then with modern cetaceans (whales, dolphins and porpoises) from 34 million years ago.”

Yet another paper in the latest Science, authored by the University of Otago’s Felix Marx and George Mason University‘s Mark Uhen, found that diatoms, a common type of phytoplankton, along with climatic events, influenced the evolution of cetaceans once they headed into the water.

Marx and Uhen believe that “a great increase in diatom-based productivity, possibly by increasing the bioavailability of silica and other nutrients in the Southern Ocean and coastal upwelling zones around the world through deep-mixing occurring around Antarctica” drove the evolution of baleen whales, in particular.

The research sheds light on why marine mammals that can weigh over 190 short tons and grow to 108 feet in length may subsist on minuscule diatoms and other tiny, yet prevalent, water dwellers, such as krill.

See also here.

New marine plant identification guide for Panama’s Eastern Pacific: here.

7 thoughts on “Giant filter-feeding fish of the dinosaur age

  1. http://www.kansan.com/news/2010/feb/18/meet-bonnerichthys-100-million-old-fish/?news

    Meet Bonnerichthys, a 100-million-year-old fish

    By Nancy Wolens

    Originally published February 18, 2010 at 12:57 p.m., updated February 18, 2010 at 12:57 p.m.

    This rendering, by Robert Nichols, shows Bonnerichthys, a 100-million-year old giant plankton-eating fish that was classified with the help of a KU researcher. Researchers used an ancient skeletal fossil of the 18-foot fish, which was found in Western Kansas.

    Larry Martin refers to the fish as a “gentle giant in a sea of monsters.” It was discovered to be journeying through the ancient seas more than 100-million-years ago, in the age of the dinosaurs.

    After thoroughly studying prehistoric fossils of the animal, Larry Martin, senior curator of Vertebrate Paleontology at the University’s Natural History Museum, and an international team of researchers revealed what was a giant plankton-eating bony fish. a lineage of fish that had evidently been missing from the Mesozoic realm of the seas until now.

    Martin and his team were featured in the journal “Science,” published Thursday.

    While Martin’s research team had studied fish fossils in other places, it was their finding of a critical fossil in western Kansas that made the whole study complete.

    FISHING FOR FISH

    Fossils of these fish had been found before but researchers didn’t realize what they were, Martin said. The fish it most resembled was a Protosphyraena, a genus of ancient swordfish, he said.

    The team of six used new fossils from the United States, Europe and Asia but Martin obtained the most critical fossil, the skeleton of the fish in western Kansas.

    “I knew it was a fish we really didn’t know that much about,” Martin said, ”and we had acquired almost a whole skull.”

    Because the fish didn’t have a long snout and fang-like teeth, researchers were able to distinguish the difference between it and the ancient swordfish.

    “With a blunt massive head, the fish had long toothless jawbones and long gill-supporting bones that are characteristic of plankton feeding fish,” Shimada said.

    Skeletal fossils of ancient fish are rare because most of the animal’s skeleton is made out of cartilage and, over time, the cartilage disintegrates, Martin said.

    Martin and a specialist who makes castes of fossils prepared the specimen’s bones to be studied.

    Martin said they would eventually have the model on display at the Natural History Museum on campus.

    FINDING THE FOSSIL

    Years ago Martin purchased a number of fossils — one of which happened to be from the giant plankton-eating fish — from the Marion Bonner family, a fossil-collecting family that has fossils in museums throughout the U.S.

    Orville Bonner, a retired Vertebrate Paleontology preparator for the University, said the significant fossil of the giant planktivore was uncovered from the Niobrara Chalk, a fossil collecting site in Western Kansas in 1971 by his father Marion Bonner. Orville Bonner said they knew immediately they had discovered something unique

    “It had huge eyes and they were about as large as a volleyball,” he said.

    Martin and the team named the fish Bonnerichthys after the Marion Bonner’s noteworthy discovery.

    Orville Bonner, who is the oldest of eight other siblings and currently lives in Lawrence, said his family has been collecting fossils from the chalk canyons in Kansas since 1925.

    Martin said the Niobara Chalk is a distinct landmark, where scientists have been collecting fossils since 1870.

    “It’s most famous for its marine deposits from the age of the ancient dinosaurs,” Martin said.

    The phytoplanktons that the giant planktivore ate are tiny but are often quite plentiful.

    “This is telling you that the old western interior sea was really very lush,” Martin said. “The only way you can have a big animal like this is if there is an awful lot of organisms to fill the water.”

    LIFE OF THE BONNERICHTHYS

    Martin said modern, giant planktivores, such as manta rays and blue whales, are very common in today’s oceans.

    “They seemed to be absent in the seas of the ancient dinosaurs but now we’ve discovered that not only were they around,” Martin said, “but they were around and important for about 100-million-years.”

    Team member Kenshu Shimada, associate professor of environmental and biological science at DePaul University and research associate in Paleontology at the Sternberg Museum of Natural History at Fort Hays State University, said the fish was most likely surrounded by many formidable predators, such as large meat-eating sharks and marine lizards but the planktivore had the ability to protect itself.

    “The plankton-eating fish possessed well developed fore fins equipped with a blade-like margin and a sharp point that likely served as an effective defense system.”

    Martin and his team estimate the fish to be about 18 feet long — the head around three to four feet and its fins about three feet long.

    “I’d be scared to swim with it even though I realized it was only eating phytoplankton,” Martin said. “It’s a big, spectacular animal and nobody knew it was there. It’s a big deal.”

    The article, ‘100-Million-Year Dynasty of Giant Planktivorous Bony Fishes in the Mesozoic Seas,’ was featured in today’s Science magazine, published by the American Association for the Advancement of Science.

    Like

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