Whacking Day 20 million BC

Let’s say you’re a dolphin living in the shallow, tropically warm waters of 20 or so million years ago with a freakishly long snout.

What better way to catch your prey than to give it a good whack?

That is just what the appropriately named Zarhachis flagellator (I know, right!) and his cousins did, according to findings by a team of palaeontologists from the Australian Museum Research Institute (AMRI), the University of New South Wales and the Smithsonian Institution’s National Museum of Natural History in Washington DC.

The prehistoric long-snouted dolphin is now long extinct thanks to 2.58 million years of glaciation in what amounts to a salutary lesson about the dangers of climate change.

But its fossils can still teach us valuable lessons.

“The prehistoric long-snouted dolphins fed in a similar way to marlin and swordfish, sweeping their snouts through the water to hit and stun fish,” says AMRI’s Matthew McCurry the study’s lead author.

Come on, I hear you ask, how can they possibly know how an extinct dolphin hunted just by looking at its skull?

“Palaeobiologists infer the behaviour and ecology of extinct species by looking at the shape of their bones,” says Dr McCurry.

“We can do this in a couple of different ways. We can study the association between structure and function in living species, to figure out how the shape of their bones influences their abilities before applying these patterns to extinct species. Alternatively, we can use mechanical principles to figure out the limitations of their abilities. For example, how much force can a certain shaped snout handle before it breaks.

Dr McCurry says the ancient dolphins had “extremely long snouts”, up to 1m long.

“They are really unusual looking animals dating from the Neogene Period, some 2.5-20 million years ago.” 

“In one species the snout is more than five times as long as the rest of the skull. It’s a really unusual trait,” he says. 

“These species used their long snouts to sweep quickly through the water to catch small agile fish.” 

This is the first study to focus on what these species were feeding on, and why they might have gone extinct. 

“The study represents a significant contribution to understanding how and why our ocean animals have changed over time.” 

Lead researcher Dr. Matthew McCurry holds Zarhachis flagellator fossil | Photograph provided by Australian Museum Research Institute (AMRI)

He says that thanks to the study we now have a better understanding of what these species were doing in the environment and why they aren’t around today. 

“Our findings show that changes in climate can have a big impact on our ocean’s predators.” 

So what’s our best guess about why the dolphins became extinct when the Pliocene era, rolled around? 

“All our theories are linked to the climate becoming more erratic, which could have influenced the availability of their prey or the environments that they live in. 

“This study paints a cautionary tale. Rapid changes in climate can have large impacts on the ability of animals to survive.”

Don't miss the Australian Museum's Whales | Tohora Exhibition - come face to face with the world's largest animals, the giants of the ocean. 

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