What did Gunnar Save-Soderbergh discover in Nova Scotia as noted in the nonfiction book, Your Inner Fish?

Gunnar Save-Soderbergh was a Swedish paleontologist in the 1920s. His work led him to the fossil of a creature that was a link between fish and amphibian. He made his discovery in the fossil-rich eastern coast of Nova Scotia that was to lure many scientists including Neil Shubin in the years that followed. Save-Soderbergh’s first discover was called ichthyostega but it did not contain any history of amphibian-like limbs. However, his second discovery, the Acanthostega gunnari, had fingers and toes on its flipper-like limbs. That discovery was a phenomenal one.