Research Tracks Ancient History of Manatees and Were They Really Come From

While just four species of slow-moving aquatic herbivores of the order Sirenia remain on the planet, many different types of sea cows have existed for the previous 47 million years.

Sea cows have inhabited the shores of every continent except Antarctica, and multiple species have coexisted during periods.

A new article has compiled the most thorough history of these strange species' ancestors to date.

The ancient history of manatees

(Photo : Maegan Luckiesh/Unsplash)

Manatees and dugongs are referred to as "sea cows" by zoologists, but a quick online search may yield the more amusing moniker "floaty potatoes," as per ScienceDaily.

Imagine a 24,000-pound version swimming in the Bering Sea, twice the size of an elephant.

Only four species of the order Sirenia's round, slow-moving aquatic herbivores survived on Earth, all of which are considered vulnerable to extinction.

However, fossil evidence revealed that many distinct types of sea cows lived in the past and that multiple species coexisted at times.

Sea cows have lived along the coasts of every continent save Antarctica during their lengthy existence.

New research published today in the open access journal PeerJ tells the fullest tale yet of these strange species' ancestors.

According to co-author Steven Heritage of the Duke Lemur Center's Museum of Natural History, the earliest known fossil sea cows are about 47 million years old and lived along the coastlines of northern Africa in the proto-Mediterranean Sea.

According to the findings, this first appearance occurred approximately 11 million years after the sea cow lineage separated from their closest surviving cousins, elephants.

Elephants' earliest fossil ancestors were also from Northern Africa and lived during the early Cenozoic period, which followed the extinction of the dinosaurs.

While current manatees and dugongs have no hind limbs and are only found in the sea, the oldest known fossil sea cows had four limbs and could walk on land.

The study compiled the most comprehensive collection of extant and fossil species to date, including DNA, anatomy, location, and geologic periods.

The team's investigations comprised time-scaled statistical models for sea cow ancestry and historical biogeography models that determined the ages and paths of their migrations across Earth's oceans.

A considerable area of northern South America has been covered by fresh water wetlands for much of the last 20 million years; they finally gave rise to the Amazon River system, with draining into the South Atlantic Ocean commencing only a few million years ago.

The age of that migration corresponds to the Eocene-Oligocene boundary, a time of rapidly cooling climate and widespread and severe extinctions of numerous animal species both on land and in the sea.

After that, the Eastern Hemisphere's ancestral sea cows declined precipitously and eventually vanished.

However, the Western Hemisphere lineage that emerged towards the start of the Oligocene period gave rise to several species of sea cows that thrived and lasted for tens of millions of years, sometimes living in communities of many species.

Also Read: Florida Manatee Population Continues to Drop as Food Sources Dried Up

The sea cow that inspired mermaid legends has been declared extinct in China

Dugongs are peaceful creatures that can be observed nibbling on seagrass and gliding gently across the sea, as per Economic Times.

Researchers interviewed 788 people living in China's coastal areas to see if anyone had seen them.

For the past 23 years, there have been no reports of dugong sightings. Only three people had seen one in the previous five years.

Since 2000, there have been no documented sightings by scientists.

They are frequently spotted close to shore in shallow waters, making their habitat ideal for hunters.

Many hunters continued to catch the creature for its bone, skin, and flesh throughout the twentieth century.

Due to their rapid population reduction, they were granted grade-one national important protected animal status in 1988.

Researchers believe that natural habitats are being destroyed, notably the loss of seagrass meadows.

According to the United Nations Environment Programme, approximately 7% of seagrass habitats are lost globally each year.

The deterioration of this habitat is caused by industrial pollution, coastal development, unchecked fishing, coastal development, and many other factors.

A lack of food also caused a dramatic population decline.

Dugongs can be found in 37 tropical zones but are classified as "vulnerable." According to Professor Turvey, co-author of this study, it is a tragic loss, and other countries should take this as a warning.

He described it as a reminder that extinctions might occur before conservation policies are implemented.

Countries will gather in New York to sign a UN marine accord that will designate 30% of the world's ocean as protected.

Related article: The Return of the Manatees! Singapore-Born Sea Cows Back in the Caribbean After a Century of Extinction