HMN 2025: How Fossils reveal sea cows have engineered Arabian Gulf’s seagrass ecosystems for over 20 million years

Today, the Arabian Gulf is home to manatee-like marine mammals called dugongs that shape the seafloor as they graze on seagrasses. A newly described fossil site in Qatar reveals that ancient sea cows engineered aquatic ecosystems in a similar way more than 20 million years ago.

In a paper published in the journal PeerJ, researchers at the Smithsonian’s National Museum of Natural History worked with collaborators at Qatar Museums to also name a new species of sea cow that was a miniature version of living dugongs.

“We discovered a distant relative of dugongs in rocks less than 10 miles away from a bay with seagrass meadows that make up their prime habitat today,” said Nicholas Pyenson, the curator of fossil marine mammals at the National Museum of Natural History who helped lead the new study.

“This part of the world has been prime sea cow habitat for the past 21 million years—it’s just that the sea cow role has been occupied by different species over time.”

With a burly build and a downturned snout lined with sensitive bristles, dugongs (Dugong dugon) today resemble their relatives, manatees. The one key difference between these aquatic herbivores, which are often called sea cows, is their tails: a manatee’s tail is rounded like a paddle while a dugong’s fluked tail is more similar to that of a dolphin (however, dugongs and manatees are more closely related to elephants than they are to dolphins, whales and porpoises).

Dugongs inhabit coastal waters from western Africa through the Indo-Pacific and into northern Australia. The Arabian Gulf is home to the largest individual herd of dugongs in the world, where the sea cows serve as important ecosystem engineers.

As they munch on seagrass, dugongs reshape the seafloor by creating feeding trails that release buried nutrients into the surrounding water for other aquatic animals and plants to use.

Fossils reveal that ancient dugong relatives have grazed on aquatic vegetation around the world for some 50 million years. However, their future in the Gulf is tenuous. The marine mammals are accidentally caught by local fishermen, and the coastal waters where they reside are impacted by pollution and development. The Gulf’s seagrass meadows that dugongs rely on are also affected by rising temperatures and salinity levels.

According to Ferhan Sakal, an archaeologist who is the head of excavation and site management at Qatar Museums and a co-author of the new paper, key insights into the fate of dugongs and seagrasses in the Gulf are preserved in the region’s rocks.

“If we can learn from past records how the seagrass communities survived climate stress or other major disturbances like sea-level changes and salinity shifts, we might set goals for a better future of the Arabian Gulf,” he said.

Fossil discoveries at Al Maszhabiya site

Because delicate blades of seagrass rarely fossilize, researchers must glean insights into past marine ecosystems from the sturdier bones of ancient herbivores.

Few places preserve as many of these bones as Al Maszhabiya, a fossil site in southwestern Qatar. The bonebed was initially discovered when geologists conducted mining and petroleum surveys in the 1970s and noted abundant “reptile” bones scattered across the desert. In the early 2000s, paleontologists returned to the area and quickly realized that the fossils were not from ancient reptiles but sea cows.

“The area was called ‘dugong cemetery’ among the members of our authority,” Sakal said. “But at the time, we had no idea just how rich and vast the bonebed actually was.”

After receiving the necessary permits in 2023, Pyenson, Sakal and their colleagues conducted a survey of Al Maszhabiya’s fossils. Based on the surrounding rocks, the team dated the bonebed to the Early Miocene epoch, around 21 million years ago. The team uncovered fossils that revealed that this area was once a shallow marine environment inhabited by sharks, barracuda-like fish, prehistoric dolphins and sea turtles.

These waters were also home to sea cows. The team identified more than 170 different locations containing sea cow fossils throughout the Al Maszhabiya site. According to Pyenson, this makes the bonebed the richest assemblage of fossilized sea cow bones in the world.

Al Maszhabiya even rivals famed marine mammal deposits like Cerro Ballena, a site in Chile’s Atacama Desert where Pyenson and other researchers uncovered an ancient graveyard of stranded whales.

Characteristics of ancient sea cows

The fossilized bones at Al Maszhabiya resembled the skeletons of living dugongs. However, the ancient sea cows still possessed hind limb bones, which modern dugongs and manatees have lost through their evolution. The site’s prehistoric sea cows also had a straighter snout and smaller tusks than their living relatives.

The researchers described Al Maszhabiya’s fossil sea cows as a new species, Salwasiren qatarensis. The genus name “Salwasiren” references the Bay of Salwa, a nearby area of the Gulf where dugongs live. While the Bay of Salwa spans the waters of multiple countries, the team specifically honored the State of Qatar as the site where the new sea cow was found with the species name “qatarensis.”

“It seemed only fitting to use the country’s name for the species as it clearly points to where the fossils were discovered,” Sakal said.

At an estimated 250 pounds, Salwasiren would have weighed as much as an adult panda or a heavyweight boxer, according to Pyenson. But it was still among the smaller sea cow species ever discovered. Some modern dugongs are nearly eight times heavier than Salwasiren.

Based on the fossils, the researchers posit that this region contained plentiful seagrass beds more than 20 million years ago, during a time in Earth’s history when the Gulf was a hotspot for biodiversity. Tending to these aquatic pastures were sea cows.

“The density of the Al Maszhabiya bonebed gives us a big clue that Salwasiren played the role of a seagrass ecosystem engineer in the Early Miocene the way that dugongs do today,” Pyenson said. “There’s been a full replacement of the evolutionary actors but not their ecological roles.”

And it is possible that Salwasiren was not the only species filling this role. According to Pyenson, sea cow fossils are often found grouped together among different species, making it plausible that the Al Maszhabiya bonebed could yield additional species of dugong relatives.

Conservation, heritage and digital preservation

Sakal hopes that the ongoing collaboration between Qatar Museums and the Smithsonian will help lead to future discoveries at Al Maszhabiya and nearby sites. But the first step is protecting the area’s rich fossil heritage. Sakal and his colleagues are planning to nominate the area for protection as a UNESCO World Heritage site.

“The most important part of our collaboration is ensuring that we provide the best possible protection and management for these sites, so we can preserve them for future generations,” Sakal said.

“Dugongs are an integral part of our heritage, not only as a living presence in our waters today, but also in the archaeological record that connects us to generations past,” said Faisal Al Naimi, study co-author and director of the Archaeology Department at Qatar Museums, referencing the abundant zooarchaeological sites with dugong bones throughout the Gulf.

“The findings at Al Maszhabiya remind us that this heritage is not confined to memory or tradition alone, but extends deep into geologic time, reinforcing the timeless relationship between our people and the natural world. In preserving and studying these remarkable creatures, we are also safeguarding a narrative that speaks to our nation’s identity, resilience and enduring connection to the sea.”

To preserve and make data from their research widely accessible, Pyenson and Sakal, in collaboration with the Smithsonian’s Digitization Program Office, digitally scanned several of the fossil sites they studied as well as the fossil skull, vertebrae, a tooth and other skeletal elements of the newly described ancient dugong species.

Digital 3D models of the scans are available for the public to view and explore via the open-source Smithsonian Voyager platform, including interactive educational experiences about the research team’s findings and a 3D tour showing the fossil excavation process.

In addition to Pyenson and Sakal, the study includes authors affiliated with the Smithsonian’s Digitization Program Office; the Stone Ridge School of the Sacred Heart; Texas A&M University at Galveston; Texas A&M University, College Station; and the Natural History Museum of Los Angeles County.

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