Discoveries reveal Arabian Gulf hosts both ancient fossil bed containing newly identified sea cow species and world’s largest living dugong herd
Two new studies co-authored by a Texas A&M at Galveston biologist reveal Qatar as a 20-million-year hot spot for dugongs past and present.
In the Arabian Gulf, thousands of dugongs gather each winter in the vast seagrass meadows off northwest Qatar, forming the largest herd of these marine mammals ever recorded. Just 10 miles away, a newly described fossil site preserves the remains of ancient sea cows, showing the region has supported the animals’ evolution for more than 20 million years.
These discoveries, described in two new studies co-authored by Texas A&M University at Galveston marine biologist Dr. Christopher Marshall, underscore the importance of the Arabian Gulf as a prime habitat for dugongs, which live in coastal waters from western Africa through the Indo-Pacific and into Northern Australia.
One of the studies, published today in PeerJ, identifies a new species of ancient sea cow from a dense fossil bonebed. The site contains more than 170 fossil localities from the Early Miocene and preserves the most complete dugong fossil assemblage ever documented in Qatar — including the first skull recovered from the region.
Marshall, a regents professor of marine biology, served as a dugong expert for the team of international researchers led by the Smithsonian’s National Museum of Natural History. The new fossil record in combination with the herd observations “adds another piece to the puzzle” in understanding the importance of the region for the animals, he said.
Not far from the bonebed where the new species was discovered, Marshall and colleagues from Qatar University surveyed coastal waters in 2019 and 2020 and observed winter gatherings of about 2,000 dugongs, making it the largest single aggregation documented anywhere in the world. The findings were recently published in Frontiers.
Marshall said dugongs usually don’t form in large groups, making the herd documented between Qatar and Bahrain exceptionally rare. “We’ve always had a large number of dugongs here, and for some reason they congregate in a large herd,” he said. “That does not happen anywhere else in the world, only here.
“It turns out this area has been a prolific and really important hot spot for sea cows for 20 million years,” Marshall said. “Dugongs are endangered, so it’s important to understand their evolutionary history as well as the importance of these different areas around the world for their survival.”
Commonly known as sea cows, these aquatic herbivores closely resemble their relatives, manatees. Importantly, Marshall said dugongs serve as “ecosystem engineers.”
The animals uproot the sea grasses they feed on, creating feeding trails that release nutrients that are beneficial to both sea grasses and other aquatic animals. The disruption dugongs make to the seafloor also helps maximize the biodiversity of sea grasses that are nursery grounds for many commercially and recreationally important fish, he said.
For millions of years, dugongs have relied on the seagrass meadows of the Arabian Gulf, the hottest sea in the world. Marshall calls the semi-enclosed sea a “laboratory for climate change.” In addition to losing about two meters of water per year to evaporation, the Gulf has high salinity levels, making it a difficult place for some organisms to survive.
The fact that large modern dugong groups have been documented in the area persistently for about 30 years, even as the Gulf has been heavily developed for oil and natural gas, bodes well for their resilience, Marshall said. But their future in the region is still fragile.
“This area has been losing its coral reefs in the last 20 years, and it’s slowly dying, really. The dugongs are still doing pretty well, but a lot more work needs to go in to study them to understand how large the population is,” Marshall said. “Fisheries bycatch that kill dugongs is a real issue, and the level of bycatch mortalities might be unsustainable in the near future. Their future is in peril.”
Marshall has conducted dugong research in Qatar since 2013 and was introduced to the Al Maszhabiya fossil bed in the southwestern part of the country in 2015. He visited the site a few years later with Nicholas Pyenson, the curator of fossil marine mammals at the National Museum of Natural History. Pyenson, along with colleagues including Ferhan Sakal, an archaeologist and head of excavation and site management at Qatar museums, went on to conduct a survey of Al Maszhabiya’s fossils in 2023.
Based on the surrounding rocks, the team dated the bonebed to the Early Miocene epoch around 21 million years ago. Along with fossils revealing the area was once a shallow marine environment home to sharks, barracuda-like fish, prehistoric dolphins and sea turtles, the team identified more than 170 locations containing sea cow fossils throughout the site.
The researchers described these ancient fossil sea cows as a new species, Salwasiren qatarensis. While they resemble the skeletons of living dugongs, the fossils at Al Maszhabiya still had hind limb bones; modern dugongs and manatees have lost theirs through evolution. The fossils also had straighter snouts and smaller tusks than their living relatives.
Marshall, who served as a dugong expert for the team, said this is the most complete dugong fossil group to be documented in Qatar. Salwasiren would have weighed an estimated 250 pounds, nearly eight times smaller than modern dugongs.
“There have been multiple lines of dugong families that have evolved one after another, which means this area is really good for this type of herbivorous mammal,” Marshall said. “And when you look at the evolution over time, this turns out to be a world hot spot.”
Toni Mooney Smith
Texas A&M University at Galveston
[email protected]