Featured Research

from universities, journals, and other organizations

Ancient shark fossil reveals new insights into jaw evolution

Date:
April 16, 2014
Source:
American Museum of Natural History
Summary:
The skull of a newly discovered 325-million-year-old shark-like species suggests that early cartilaginous and bony fishes have more to tell us about the early evolution of jawed vertebrates -- including humans -- than do modern sharks, as was previously thought. The new study shows that living sharks are actually quite advanced in evolutionary terms, despite having retained their basic 'sharkiness' over millions of years.

This photo shows the exceptionally well-preserved fossil of Ozarcus mapesae from two different lateral views. The scale bar is 10 millimeters.
Credit: Copyright AMNH/F. Ippolito

The skull of a newly discovered 325-million-year-old shark-like species suggests that early cartilaginous and bony fishes have more to tell us about the early evolution of jawed vertebrates -- including humans -- than do modern sharks, as was previously thought. The new study, led by scientists at the American Museum of Natural History, shows that living sharks are actually quite advanced in evolutionary terms, despite having retained their basic "sharkiness" over millions of years. The research is published today in the journal Nature.

"Sharks are traditionally thought to be one of the most primitive surviving jawed vertebrates. And most textbooks in schools today say that the internal jaw structures of modern sharks should look very similar to those in primitive shark-like fishes," said Alan Pradel, a postdoctoral researcher at the Museum and the lead author of the study. "But we've found that's not the case. The modern shark condition is very specialized, very derived, and not primitive."

The new study is based on an extremely well-preserved shark fossil collected by Ohio University professors Royal Mapes and Gene Mapes in Arkansas, where an ocean basin once was home to a diverse marine ecosystem. The fossilized skull of the new species, named Ozarcus mapesae, along with similar specimens from the same location, were part of a recent donation of 540,000 fossils from Ohio University to the Museum.

The heads of all fishes -- sharks included -- are segmented into the jaws and a series of arches that support the jaw and the gills. These arches are thought to have given rise to jaws early in the tree of life.

Because shark skeletons are made of cartilage, not bone, their fossils are very fragile and are usually found in flattened fragments, making it impossible to study the shape of these internal structures. But the Ozarcus mapesae specimen was preserved in a nearly three-dimensional state, giving researchers a rare glimpse at the organization of the arches in a prehistoric animal.

"This beautiful fossil offers one of the first complete looks at all of the gill arches and associated structures in an early shark. There are other shark fossils like this in existence, but this is the oldest one in which you can see everything," said John Maisey, a curator in the Museum's Division of Paleontology and one of the authors on the study. "There's enough depth in this fossil to allow us to scan it and digitally dissect out the cartilage skeleton."

Working with scientists at the European Synchrotron, the ESRF, Pradel imaged the specimen with high-resolution x-rays to get a detailed view of each individual arch shape and organization. "We discovered that the arrangement of the arches is not like anything you'd see in a modern shark or shark-like fish," said Pradel. "Instead, the arrangement is fundamentally the same as bony fishes."

The authors say it's not unexpected that sharks -- which have existed for about 420 million years -- would undergo evolution of these structures. But the new work, especially when considered alongside other recent developments about early jawed vertebrates, has significant implications for the future of evolutionary studies of this group. "Bony fishes might have more to tell us about our first jawed ancestors than do living sharks," Maisey said.


Story Source:

The above story is based on materials provided by American Museum of Natural History. Note: Materials may be edited for content and length.


Journal Reference:

  1. Alan Pradel, John G. Maisey, Paul Tafforeau, Royal H. Mapes, Jon Mallatt. A Palaeozoic shark with osteichthyan-like branchial arches. Nature, 2014; DOI: 10.1038/nature13195

Cite This Page:

American Museum of Natural History. "Ancient shark fossil reveals new insights into jaw evolution." ScienceDaily. ScienceDaily, 16 April 2014. <www.sciencedaily.com/releases/2014/04/140416133336.htm>.
American Museum of Natural History. (2014, April 16). Ancient shark fossil reveals new insights into jaw evolution. ScienceDaily. Retrieved August 21, 2014 from www.sciencedaily.com/releases/2014/04/140416133336.htm
American Museum of Natural History. "Ancient shark fossil reveals new insights into jaw evolution." ScienceDaily. www.sciencedaily.com/releases/2014/04/140416133336.htm (accessed August 21, 2014).

Share This




More Plants & Animals News

Thursday, August 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Newsy (Aug. 21, 2014) — An experimental drug used to treat Marburg virus in rhesus monkeys could give new insight into a similar treatment for Ebola. Video provided by Newsy
Powered by NewsLook.com
Terrifying City-Dwelling Spiders Are Bigger And More Fertile

Terrifying City-Dwelling Spiders Are Bigger And More Fertile

Newsy (Aug. 21, 2014) — According to a new study, spiders that live in cities are bigger, fatter and multiply faster. Video provided by Newsy
Powered by NewsLook.com
Ramen Health Risks: The Dark Side of the Noodle

Ramen Health Risks: The Dark Side of the Noodle

AP (Aug. 21, 2014) — South Koreans eat more instant ramen noodles per capita than anywhere else in the world. But American researchers say eating too much may increase the risk of diabetes, heart disease and stroke. (Aug. 21) Video provided by AP
Powered by NewsLook.com
California Drought Stings Honeybees, Beekeepers

California Drought Stings Honeybees, Beekeepers

AP (Aug. 21, 2014) — California's record drought is hurting honey supplies and raising prices for consumers. The lack of rainfall means fewer crops and wildflowers that provide the nectar bees need to make honey. (Aug. 21) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins