Further evidence that the Antarctic Peninsula was once a warm, humid region with a wealth of plant and animal diversity has been discovered in the form of the earliest known evidence of Antarctic amphibians. The discovery, published in the journal Scientific Reports, details fossilized specimens that belong to the family of helmeted frogs.

Before its separation from the southern supercontinent, Gondwana, the Antarctic Peninsula was a temperate region rich in diversity and populated with an entirely different cast of animals to those we see today.

The fossils were uncovered by Thomas Mörs and colleagues from the Swedish Museum of Natural History during expeditions to Seymour Island between 2011 and 2013. They found evidence of an amphibian hip bone and ornamented skull bone from the frog family Calyptocephalellidae, both from the Eocene period around 40 million years ago.

Reconstruction of Eocene helmeted frog on the Antarctic Peninsula. Credits: Artwork by Pollyanna von Knorring, Swedish Museum of Natural History. Photo credits: Simon Pierre Barrette and José Grau de Puerto Montt, Wikimedia Commons (CC BY-SA 3.0), and Mats Wedin, Swedish Museum of Natural History.

It was previously believed that the Antarctica Peninsula became a colossal sheet of ice before the final division of the supercontinent Gondwana, which also included Africa, South America, Antarctica, Australia, and the Arabian Peninsula. The break up occurred around 180 million years ago, giving rise to Antarctica and South America. However, this amphibian fossil evidence indicates that the Antarctic Peninsula was in fact as humid as we know South America to be today.

The discovery of this particular family of amphibians is significant as all extant species of helmeted frogs exist exclusively within South America today. Their presence in Antarctica therefore paints a far warmer picture for its past climate than the icescape today.

Palaeontologists at the frog site on Seymour Island. Credits: Federico Degrange, Centro de Investigaciones en Ciencias de la Tierra and Jonas Hagström, Swedish Museum of Natural History.

The similarities between their resident amphibian species may indicate that Eocene Epoch Antarctica was similar to the forests of modern-day South America before the glaciation event that turned it into the Peninsula we know today. It’s therefore possible that species found in South America today could inform which animals were originally found across the Antarctic Peninsula.

A recent analysis of soil in the region further supports this picture of a toastier climate in Antarctica’s past, as evidence of root systems, pollen, and spore varieties suggest there was likely no icecap present at the time. The analysis used climate models to ascertain what kind of conditions would’ve been needed to support such rich plant life, which put the summer temperature estimates at around 19°C (66°F).

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