Marsileaceae are one of two families of aquatic to semi-aquatic, heterosporous ferns that comprise the order Salviniales. The three genera in the family – Marsilea, Pilularia, and Regnellidium – are easily distinguished on the basis of leaf and megaspore morphology. While Marsileaceae have an extensive spore record that dates back to the Late Jurassic to earliest Early Cretaceous, the poverty of their macrofossil record makes it difficult to determine how their sporophyte structure has evolved over time and whether changes in spore and sporophyte morphology are coincident or staggered. Recent finds from the Upper Cretaceous La Colonia Formation of Patagonia, Argentina, have provided new macrofossil and spore records of water ferns. This has spurred further investigation into the macrofossil record of North American Marsileaceae, including reexamination of the most ancient known plant with Marsilea-like leaves, Marsileaceaephyllum johnhallii. Findings indicate that this important taxon may actually represent the enigmatic Cretaceous-Paleogene angiosperm Fortuna. With the loss of this record, Marsilea-like leaves are represented by only three known macrofossil occurrences worldwide; with the addition of a new species of Regnellidium from the La Colonia Formation, Regnellidium leaves are known from two. Thus, while the fossil record presents tantalizing clues about the morphological evolution of the heterosporous ferns, the macrofossil record of Marsileaceae remains vague and prone to misinterpretation.
Host: Professor Yin-long Qiu
Coffee and snacks will be served at 4 p.m.