In 2015, Thomas Mörs reached for a frog in the sand — but the frog didn’t hop away. That’s because the frog had been fossilized 40 million years ago. Nevertheless, Dr. Mörs knew that the frog would soon be hopping into history books, because it was the first fossil frog from Antarctica ever found.

“When I was going through samples and I saw this, I said: ‘Wow! That’s a frog!’” said Dr. Mörs, a vertebrate paleontologist at the Swedish Museum of Natural History who led the team of researchers that announced the find Thursday in Scientific Reports. “I knew nothing like this was known from Antarctica. It’s exciting.”

Dr. Mörs and his team retrieved the frog from Seymour Island, which sits on the Antarctic Peninsula roughly 700 miles south of Tierra Del Fuego on South America. The frog came to light in 2015 back in Sweden after Dr. Mörs had time to sift through the thousands of samples he and his team collected during expeditions to the island in 2011, 2012 and 2013. The haul also included fossilized water lily seeds and shark and ray teeth.

Dr. Mörs found two frog bones: a skull and a hip bone called an ilium. “The ilium is probably the most diagnostic part of a frog skeleton,” said David Wake, a herpetologist at the University of California, Berkeley, who was not involved in the research. “A frog paleontologist wants an ilium.”