A unique fossil of a 20 million-year-old salamander has been found encased in a chunk of amber from an unlikely place – the Dominican Republic, where all salamanders are now extinct.

The piece of amber containing the fossil is hemispheric in shape, measuring 20 mm in length, 8 mm in greatest width and 8 mm in depth. It came from an amber mine in the northern mountain range of the Dominican Republic, between Puerto Plata and Santiago.

“I was shocked when I first saw it in amber. There are very few salamander fossils of any type, and no one has ever found a salamander preserved in amber,” said Prof George Poinar, Jr., of Oregon State University, lead author of a paper published in the journal Palaeodiversity.

“And finding it in Dominican amber was especially unexpected, because today no salamanders, even living ones, have ever been found in that region.”

The salamander, named Palaeoplethodon hispaniolae, belonged to Plethodontidae – a widespread family of salamanders that today is still very common in North America, particularly the Appalachian Mountains.

“It had back and front legs lacking distinct toes, just almost complete webbing with little bumps on them. As such, it might not have been as prolific a climber as some modern species and it probably lived in small trees or tropical flowering plants,” Prof Poinar said.

“The discovery of this fossil shows there once were salamanders in the Caribbean, but it’s still a mystery why they all went extinct. They may have been killed by some climatic event, or were vulnerable to some type of predator.”

“Also a mystery is how salamanders got there to begin with. The physical evidence suggests the fossil represents an early lineage of phethodon salamanders that evolved in tropical America,” Prof Poinar said.

The lineage of Palaeoplethodon hispaniolae may go back 40-60 million years ago when the Proto-Greater Antilles, that now include islands such as Cuba, Jamaica, Puerto Rico and Hispaniola, were still joined to North and South America.

“Salamanders may have stayed on the islands as they began their tectonic drift across the Caribbean Sea. They also may have crossed a land bridge during periods of low sea level, or it’s possible a few specimens could have floated in on debris, riding a log across the ocean,” Prof Poinar said.

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George Poinar Jr. & David B. Wake. 2015. Palaeoplethodon hispaniolae gen. n., sp. n. (Amphibia: Caudata), a fossil salamander from the Caribbean. Palaeodiversity 8: 21-29