A mid-Cretaceous tree fern of Thyrsopteridaceae (Cyatheales) preserved in Myanmar amber

An unusual tree fern trapped in mid-Cretaceous Myanmar amber is described as Thyrsopteris cretacea sp. nov. (Thyrsopteridaceae). The fossil most resembles T. elegans, a present-day species endemic to the Juan Fernández Islands, based on the character combination of pinnate fertile lamina segments with short lobes bearing terminal sori, cyathiform indusia, clavate receptacles, and oblique annuli. Thyrsopteris cretacea is the first described mid-Cretaceous tree fern preserved in amber. It adds to the diversity previously ascribed to the Thyrsopteridaceae, which has been based on Eocene fossils, and it extends the fossil record of the family further back to the mid-Cretaceous. Most previous fossils of Thyrsopteridaceae have been from the Southern Hemisphere and are therefore considered Gondwanan. Thyrsopteris cretacea represents one of the few occurrences of the family in Laurasia.