Fossils of a new species of pygmy pipehorse—a relative of the seahorse—have been discovered in Slovenia, a new study says.
Scientists discovered the 1-inch-long (2.5-centimeter-long) species—dubbed Hippotropiscis frenki—in a fossil-rich region called the Tunjice Hills, where the team also found the oldest known seahorse fossils in 2009.
Pygmy pipehorses are thought to be an evolutionary link between seahorses and their close relatives, including pipefish and seadragons.
The animals share so many features that at first study leader Jure Žalohar and colleagues thought the newfound fossils belonged to another type of ancient seahorse.
Modern pygmy pipehorses also look and behave a lot like seahorses—pygmy pipehorse males, for instance, care for their fertilized eggs in a special pouch.
"The only major difference is that [pygmy pipehorses] do not swim upright," Žalohar, a geologist at the University of Ljubljana, said by email.
Photograph courtesy Jure Žalohar
The pygmy pipehorse species Acentronura breviperula, pictured in the Philippines, is one of eight species that exist today.
The newfound fossil, Hippotropiscis frenki, looks more like seahorses than living pygmy pipehorses. This resemblance may mean that the first seahorses—like the fossil pygmy pipehorse—had long tails and slim bodies and were probably less than two inches (five centimeters) long.
Previous genetic studies suggested that seahorses diverged from pygmy pipehorses and adopted an upright stance about 25 million years ago.
But since the new pygmy pipehorse fossils are just 12.5 million years old, Žalohar said the Hippotropiscis lineage could have separated from the main seahorse lineage as early as 20 million years ago.
A drawing of the new pygmy pipehorse (right) based on one of the Slovenian fossils shows how the animal may have looked in real life. H. frenki was named for Frenk Stare, a Slovenian geologist and teacher.
The extinct pygmy pipehorse likely lived among dense vegetation in warm coastal waters.
Its long dorsal fin also suggests the fish was a relatively good swimmer, which means the pygmy pipehorse "could perhaps also have lived in a more open environment, such as muddy and silty seabeds," Žalohar said.
Scientists also found a new specimen (pictured) of an extinct seahorse called Hippocampus slovenicus, one of the species discovered at the site in 2009.
H. slovenicus shares characteristics with living pygmy seahorses, including a short tail.
The team also unearthed the first fossil of a pipehorse—a larger relative of pipefish, pygmy pipehorses, and seahorses—which they hope to describe as another new species.
The fossil fish probably died during a bout of severe oxygen depletion in the lagoon, which also prevented the animals from decaying before being fossilized, according to Žalohar, whose study was published in March in the journal Annales de Paléontologie.