First water lily, a leaf of Nymphaea sp., from the Miocene Clarkia flora, northern Idaho, USA: Occurrence, taphonomic observations, floristic implications

Abstract

Although the Miocene Clarkia locality in Idaho, USA, is a well-known fossil lagerstätte, this 16-million-year-old flora is especially renowned for its abundant leaves with excellent preservation. The exquisite condition of its dicot leaves has resulted in detailed research on systematics, morphology, venation, epidermal structure, cell ultrastructure, biochemistry, and even molecular biology. However, new discoveries continue to emerge, even after five decades of research. Here we describe the first water lily leaf from the Clarkia flora as Nymphaea sp. based on its form, petiole attachment, and venation. The eccentric peltate leaf is ovate with a cordate base, a deep basal sinus, entire margins, and actinodromous primary venation. Its small, unblemished condition and leathery texture suggests that it is a young floating leaf. While rare in the Clarkia Lake deposits, the occurrence of a single water lily leaf among tens of thousands of dicot and conifer leaves follows the taphonomic pattern of nearby Middle Miocene floras, two of which have yielded Nymphaea pollen. The recognition of Nymphaea at Clarkia supplements the taxonomic composition of the flora, confirms the presence of water lilies in region during the Middle Miocene, and completes our understanding of plant life in the Pacific Northwest 16 million years ago.