Hany Mahmoud is the author.
The pig-nosed turtle is a unique freshwater turtle that is native to the Northern Territory. It is almost completely adapted to life in water. It has flippers similar to sea turtles, a snorkel-like "pig- nose" to help it breathe, and eggs that will only hatch when exposed to the waters of the wet season.
It is the last remaining species of the carettochelyids, a group of turtles that once lived in the northern hemisphere. We thought that pig-nosed turtles had only arrived in Australia within the past few millennia, as no pig-nosed turtle fossils had ever been found here.
A 5-million-year-old fossil from Museums Victoria's collections has completely rewritten the story. The fossil was unknown in the museum's collection for almost 100 years until our team found it.
We reported in the journal Papers in Palaeontology that the fossil was a small section of the pig-nosed turtle's shell. We were lucky that the fossil was from a very important area of the shell.
The carettochelyid turtles have been living in Australia for millions of years. The pig-nosed turtle is thousands of kilometers away from their modern range.
An artist's depiction of a pig-nosed turtle swimming in a river. Credit: Jaime Bran.
In the past, the weather in Melbourne was a lot nicer. It was similar to the conditions in which these turtles live today.
Monk seals, dugongs and other prehistoric tropical species have been found here, and monk seals live in Hawaii and the Mediterranean.
A tropical city?
Australia's eastern seaboard was a turtle hot spot millions of years ago. The warmer and wetter environment would have been ideal for supporting turtles. Today, Australia is mostly home to the side-necked turtles.
The turtles would have had to travel thousands of kilometers to get here. Small animals cross the sea by hitching a ride on vegetation rafts.
The location of the pig-nosed turtle fossil and distribution of Australia's freshwater turtles today. The new fossil was found at Beaumaris. Aline M. Ghilardi is the author of the turtle silhouette.
A pig-nosed turtle fossil is on the shell of a modern pig-nosed turtle. Credit: Erich Fitzgerald.
The location of the pig-nosed turtle fossil and distribution of Australia's freshwater turtles today. The new fossil was found at Beaumaris. Aline M. Ghilardi is the author of the turtle silhouette.
A pig-nosed turtle fossil is on the shell of a modern pig-nosed turtle. Credit: Erich Fitzgerald.
Where are these turtles now? The last remaining species of the carettochelyid is the pig-nosed turtle. Climate change was a threat to animals in the past. The pig-nosed turtle in the Northern Territory and New Zealand is the only one left that is still alive.
The pig-nosed turtle is under threat from climate change. Without rain, these turtles cannot hatch their eggs.
A lot of Australia's native animals and plants are this way. Sex can be determined by the temperature of the eggs at which they are being hatched. As the climate changes, this factor could put these species at risk.
The fossils from Beaumaris show how important the environment was for ancient animals. Many tropical species used to be found in southern Australia, but now they have more restricted ranges.
The discovery of monk seals fossils from Beaumaris completely changed how scientists thought seals evolved. This shows how much we still have to learn about Australia's prehistoric past, when it was a different place.
James P. Rule and his team discovered a pignosed turtle fossil from southern Australia that shows freshwater turtle invasions and extinctions. The spp 2.1414 is in the book.
The Conversation's article is a Creative Commons licensed one. The original article can be found here.
The rare fossil reveals that prehistoric Melbourne was once a paradise for tropical pig-nosed turtles.
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