Nav: Home

A rare assemblage of sharks and rays from nearshore environments of Eocene Madagascar

February 27, 2019

Eocene-aged sediments of Madagascar contain a previously unknown fauna of sharks and rays, according to a study released February 27, 2019 in the open-access journal PLOS ONE by Karen Samonds of Northern Illinois University and colleagues. This newly-described fauna is the first report of sharks and rays of this age in Madagascar.

The Mahajanga basin of northwestern Madagascar yields abundant fossil remains of terrestrial and marine ecosystems, but little is known about fossil sharks and rays during the Eocene Epoch, 55-34 million years ago, in this region. This is in contrast to the numerous shark and ray faunas known from other Eocene sites around the globe, and to shark and ray ecosystems known from older and younger sediments in the Mahajanga basin.

In this study, Samonds and colleagues collected isolated teeth, dental plates, and stingray spines from ancient coastal sediments of the Ampazony and Katsepy regions of the basin, dated to the middle to late Eocene. They identified at least 10 species of sharks and rays, including one new species, Carcharhinus underwoodi. This is the oldest named species of Carcharhinus, a genus that has been globally distributed for the past 35 million years but is known only rarely from the Eocene.

Aside from the new species, the fauna of Eocene Madagascar shares many species with Eocene ecosystems across North Africa, suggesting these animals were widespread in southern seas at that time. On the other hand, the Madagascar fauna is uniquely lacking in sandsharks and dominated by eagle rays, indicating a somewhat unusual ecosystem, unsurprising given Madagascar's long history of isolation. The authors caution that this study provides an incomplete picture given that they collected only fossils larger than 2 millimeters. They recommend that future studies target smaller material for a more complete view of the ancient ecosystem.
-end-
In your coverage please use this URL to provide access to the freely available article in PLOS ONE: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0211789

Citation: Samonds KE, Andrianavalona TH, Wallett LA, Zalmout IS, Ward DJ (2019) A middle - late Eocene neoselachian assemblage from nearshore marine deposits, Mahajanga Basin, northwestern Madagascar. PLoS ONE 14(2): e0211789. https://doi.org/10.1371/journal.pone.0211789

Funding: Funded by National Geographic Research and Exploration Grant (Karen Samonds) Standard Grants (#9662-15, #8667-09, #8125-06, #7687-04); https://www.nationalgeographic.org/topics/exploration/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

PLOS

Related Sharks Articles:

Diving with the sharks
A new study finds that humans can interact with sharks without long-term behavioral impacts for the ocean's top predators.
Study shows how skates, rays and sharks sense electrical fields
Sharks, rays and skates can hunt for prey hidden in the sandy sea floor by 'listening' for faint traces of bioelectricity -- they can literally sense their prey's heart beating.
Study finds preliminary recovery of coastal sharks in southeast US
Population gains follow enactment of fishing regulations in the early 1990s after decades of declining shark numbers.
Planned protection area would help basking sharks
A proposed Marine Protected Area off Scotland's west coast would help basking sharks, researchers say.
Counting sharks
Researchers recalibrate shark population density using data they gathered during eight years of study on Palmyra atoll.
Basking sharks seek out winter sun
The winter habits of Britain's basking sharks have been revealed for the first time.
New software will standardize data collection for great white sharks
The lack of a standardized procedure for collecting data about elusive and hard to find species like the great white shark has to date seriously hampered efforts to manage and protect these animals.
Can sharks be fished sustainably? Yes (but it's going to take work)
Conventional wisdom holds that sharks can't be harvested in a sustainable manner because they are long-lived animals.
Sharks show novel changes in their immune cancer-related genes
Research scientists at Nova Southeastern University (NSU) and Cornell University have been studying the genetics of great white and great hammerhead sharks, and their work brings us a few steps closer to understanding -- from a genetic sense -- why sharks exhibit some characteristics that are highly desirable by humans (specifically, rapid wound healing and possible higher resistance to cancers).
How sharks recycle toxic ammonia to keep their skin moist
The Pacific spiny dogfish shark is a master at recycling the ocean's toxic ammonia and converting it into useful urea, according to new research from University of British Columbia zoologists.

Related Sharks Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Changing The World
What does it take to change the world for the better? This hour, TED speakers explore ideas on activism—what motivates it, why it matters, and how each of us can make a difference. Guests include civil rights activist Ruby Sales, labor leader and civil rights activist Dolores Huerta, author Jeremy Heimans, "craftivist" Sarah Corbett, and designer and futurist Angela Oguntala.
Now Playing: Science for the People

#521 The Curious Life of Krill
Krill may be one of the most abundant forms of life on our planet... but it turns out we don't know that much about them. For a create that underpins a massive ocean ecosystem and lives in our oceans in massive numbers, they're surprisingly difficult to study. We sit down and shine some light on these underappreciated crustaceans with Stephen Nicol, Adjunct Professor at the University of Tasmania, Scientific Advisor to the Association of Responsible Krill Harvesting Companies, and author of the book "The Curious Life of Krill: A Conservation Story from the Bottom of the World".