Sporophytes, megaspores, and massulae ofAzolla stanleyifrom the Paleocene Joffre Bridge locality, Alberta

摘要

Several hundred vegetative and fertile specimens ofAzollaLam. have been recovered from the Paleocene Paskapoo Formation at the Joffre Bridge locality (Middle Tiffanian (Ti3) age) near Red Deer, Alberta. The spore complexes closely resemble those of the PaleoceneA.stanleyiJain & Hall, and the vegetative material is referred to that species. The specimens are unusually complete in that the remains of the fragile sporophyte are preserved, commonly with reproductive structures in place. Plants reaching up to 2.25 cm in length consist of alternately branched rhizomes bearing alternate, imbricate, sessile leaves. Leaves are ovate with entire margins, papillate surfaces, and a single midvein. Reproductive structures have been examined using light, scanning, and transmission electron microscopy. This new material is compared with the other Paleocene species for which sporophytes are known and discussed in terms of evolutionary trends for the genus. The specimens suggest that most of the vegetative characteristics of modernAzollaspecies were established by the middle Paleocene.Key words:Azolla, Salviniaceae, megaspore, massula, ultrastructure, Paleocene.