05 May 2009

Ancient seahorses found

Discovery of the oldest seahorse fossils to date in Slovenia may help better understand how these poor swimmers were able to spread around the globe.
Photograph and illustration courtesy Jure Žalohar

Oldest Seahorses Found; Help Solve Mystery
Charles Choi, National Geographic News 4 May 09;
Photographs and illustration courtesy Jure Žalohar
May 4, 2009--The oldest seahorse fossils discovered to date have been uncovered in Slovenia, including this two-inch-long (five-centimeter-long) adult female Hippocampus sarmaticus fossil (left, and in an artist's reconstruction, right).

The 13-million-year-old finds, which include the only known extinct seahorse species, are shedding light on how the naturally weak swimmers managed to disperse around the world.

Researcher Jure Žalohar of Slovenia's University of Ljubljana first spotted a fossil in the water as he was washing his hands in a stream after a jog.

Žalohar and colleagues were originally investigating fossil insects in this area, so finding the fossil seahorses was "completely unexpected," he said.

The findings appeared online April 17 in the French-language journal Annales de Paleontologie.

Earlier seahorses likely lived in the temperate shallow coastal waters of the passageway between Europe and Africa that linked the Atlantic with the Indian Ocean until about 15 million years ago, the researchers say. That passageway would have helped the fish slowly spread around the globe.

They probably dwelled in dense beds of seagrass, where food--such as small crustaceans--was abundant. The seahorses' black flecks would have camouflaged them in the vegetation, which the fish also likely anchored themselves to using their prehensile tails.

The abundance of newfound seahorse fossils suggests that these ancient species had broods of at least ten offspring at a time, researchers said in April 2009.

The new finds suggest that the fish could have held onto floating clumps of seagrass for weeks or months with their prehensile tails. If caught in a current, these rafts of seagrass may have carried the seahorses as far as 160 miles (260 kilometers) in a month--possibly explaining how the poor swimmers were able to spread around the globe.

In a recent expedition, scientists found seahorse fossils of different ages living near each other, probably in what were once dense beds of seagrass.

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