At The Mountains of Madness by H. P. Lovecraft

On an expedition to Antarctica, Professor William Dyer and his colleagues discover the remains of ancient half-vegetable, half-animal life-forms. The extremely early date in the geological strata is surprising because of the highly-evolved features found in these previously unkown life-forms. Through a series of dark revelations, violent episodes, and misunderstandings, the group learns of Earth's secret history and legacy