MORPHOLOGY AND PALEOECOLOGY OF RICCIOPSIS-SPEIRSAE SP. NOV. (RICCIACEAE), A FOSSIL LIVERWORT FROM THE PALEOCENE JOFFRE BRIDGE LOCALITY, ALBERTA, CANADA

More than 60 specimens of a fossil liverwort gametophyte have been rec overed from the Paleocene Paskapoo Formation at the Joffre Bridge loca lity near Red Deer, Alta. They closely resemble thalli of extant Ricci a and have been assigned to the genus Ricciopsis Lundblad. Thalli are linear and prostrate, with smooth margins and a distinct dorsal sulcus . Dichotomous branching occurs in a single plane. Ribbonlike segments reach lengths as great as 55.0 mm, with up to seven dichotomies. Width is typically 1.5-2.0 mm, but abrupt constrictions and dilations are s ometimes present proximal to dichotomies. The latter feature distingui shes this fossil from known fossil and living Ricciaceae, and thus it is referred to a new species, Ricciopsis speirsae sp.nov. Liverworts a re not common in the fossil record. Ricciopsis speirsae is the first r icciaceous fossil to be described from North America and the first of Paleocene age worldwide. The specimens are found in a layer of lacustr ine claystone, scattered among remains of a free-floating lemnaceous p lant. Both the geologic setting and the associated fossils indicate th at the environment of deposition was a shallow oxbow lake.