An osmundaceous rhizome with sterile and fertile fronds and in situ spores from the Jurassic of western Liaoning

Abstract

A well-preserved permineralized osmundaceous fern was discovered from the Middle Jurassic Tiaojishan Formation of Beipiao, Liaoning Province, China. The rhizome is about 50 cm high and 35–41 cm in diameter and can be attributed to the genus Ashicaulis on the basis of its anatomy. The sterile pinnae are referable to Cladophlebis, the fertile pinnules are of the Todites type with in situ spores of the Osmundacidites type. Osmundaceous rhizomes have been found all over the world including the Jurassic strata of western Liaoning, China. Until now, however, no rhizomes have been reported to be organically connected with leafy organs. Although impressions and compressions of isolated osmundaceous sterile and fertile fronds are common, they were described under separate organ- or morpho-generic names, such as Todites and Cladophlebis. The new discovery provides an opportunity to study an osmundaceous fern in ‘whole plant concept’ to learn more about its morphology and structure, and the paleoclimatic and paleoenvironmental requrirements of this group.