Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Ancient Sharks Reared Young in Prehistoric River-Delta Nursery

Like salmon in reverse, long-snouted Bandringa sharks migrated downstream from freshwater swamps to a tropical coastline to spawn 310 million years ago, leaving behind fossil evidence of one of the earliest known shark nurseries.

That's the surprising conclusion of University of Michigan paleontologist Lauren Sallan and a University of Chicago colleague, who reanalyzed all known specimens of Bandringa, a bottom-feeding predator that lived in an ancient river delta system that spanned what is today the Upper Midwest.

Painting by John Megahan, University of Michigan.

An artist's rendering of Bandringa, a 310 million-year-old shark originally found in fossil deposits from Mazon Creek, Illinois. University of Michigan paleontologist Lauren Sallan and a colleague say this bottom-feeding predator migrated to the ocean to spawn in shallow coastal waters and left behind fossil evidence of one of the earliest known shark nurseries

The new findings, scheduled for online publication Jan. 7 in the Journal of Vertebrate Paleontology, mark the earliest known example of shark migration—a behavior that persists today among species such as tiger sharks in Hawaii.

The Bandringa fossils, as reinterpreted by Sallan and Michael Coates, also reveal the only known example of a freshwater to saltwater shark migration, as well as the earliest example of a shark nursery where fossilized egg cases and juvenile sharks were preserved in the same sediments.

"This pushes migratory behavior in sharks way back," said Sallan, an assistant professor in the U-M Department of Ecology and Evolutionary Biology. "These sharks bred in the open ocean and spent the rest of their lives in fresh water. No shark alive today is known to do that."

The long-extinct Bandringa is likely one of the earliest close relatives of modern sharks. It resembled present-day sawfish and paddlefish, with a spoon-billed snout up to half its body length. Juveniles were 4 to 6 inches long and grew into adults of up to 10 feet.

Bandringa was discovered in 1969 and soon became one of the most prized fossils from the well-known Mazon Creek deposits in northern Illinois. Until now, researchers believed that the genus Bandringa contained two species, one that lived in freshwater swamps and rivers and another that lived in the shallow ocean.

But after reevaluating fossils from 24 individuals, including latex "peels" of Bandringa's scale-covered skin, Sallan and Coates concluded that Bandringa was a single species that lived, at various times during its life, in fresh, brackish and salt water.

The physical differences between the two purported species were due to different preservation processes at marine and freshwater locations, Sallan and Coates concluded. The freshwater sites tended to preserve bones and cartilage, while the marine sites preserved soft tissue.

By combining the complementary data sets from both types of fossil sites and reclassifying Bandringa as a single species, Sallan and Coates gained a far more complete picture of the extinct shark's anatomy and discovered several previously unreported features. They include downward-directed jaws ideal for suction-feeding off the bottom, needle-like spines on the head and cheeks, and a complex array of sensory organs (electroreceptors and mechanoreceptors) on both the extended snout and body, suited for detecting prey in murky water.

Adult Bandringa sharks lived exclusively in freshwater swamps and rivers, according to Sallan and Coates. Females apparently traveled downstream to a tropical coastline to lay their eggs in shallow marine waters, a reverse version of the modern-day salmon's sea-to-stream migration. At the time, the coastline of the super-continent Pangaea ran diagonally between the Mazon Creek freshwater and marine sites.

All the Bandringa fossils from the Mazon Creek marine sites are juveniles, and they were found alongside egg cases—protective capsules that enclose eggs of the next generation—belonging to an early species of shark. Adult Bandringa fossils have been found only at freshwater locations, including several in Ohio and Pennsylvania.

Sallan and Coates said that the juvenile Bandringa sharks hatched from the Mazon Creek egg cases, and that the deposit's marine sites represent a shark nursery where females spawned and then departed, returning upstream to freshwater rivers and swamps.

"This is the first fossil evidence for a shark nursery that's based on both egg cases and the babies themselves," Sallan said. "It's also the earliest evidence for segregation, meaning that juveniles and adults were living in different locations, which implies migration into and out of these nursery waters."

The Mazon Creek deposit is known for its extremely diverse, well-preserved fossils, with more than 320 animal species identified, according to the Illinois State Museum.

Many of those animals lived in shallow marine bays. Other plants and animals lived in swampy areas along rivers that emptied into the bay. When the remains of all these plants and animals sank to the bottom of the bay, they were rapidly buried by mud washing in from the river, which preserved them.

Financial support for the project was provided by the National Science Foundation, the University of Chicago, the University of Michigan and the Michigan Society of Fellows.

EDITORS: High-resolution images are available at

Jim Erickson | Newswise
Further information:

More articles from Life Sciences:

nachricht Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München

nachricht Second research flight into zero gravity
21.10.2016 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>