Question: What had been thought for a while to be an independent ancient Greek precursor to Twain's story?
Sentence: The latter included a synopsized adaptation of his story that Twain stated had appeared, unattributed to Twain, in a Professor Sidgwick’s Greek Prose Composition (p. 116) under the title, "The Athenian and the Frog"; the adaptation had for a time been taken for an independent ancient Greek precursor to Twain's "Jumping Frog" story.
Answer in sentence: yes