Cuticular analysis has long been used by palaeobotanists for the identification of fossil leaves, and a variety of chemical procedures has been developed to extract and prepare fossil cuticles. However, even commonly used solutions may be too harsh for the preparation of extremely delicate cuticles. Here we offer a step-by-step protocol for the preparation of fragile conifer cuticles using sodium hypochlorite, otherwise known as household bleach. Conifer needles from the Miocene lignites of the Adendorf and Hambach open-mine pits in western Germany were prepared using a mild solution of this oxidizing agent. The cuticles had proven to be too fragile for most maceration chemicals, including Schulze’s reagent, which even disintegrated the cuticles that were given a protective coating. However, it was discovered that trimming the leaf margins and damaged areas prior to a short exposure to 5–10% sodium hypochlorite solution resulted in the good preparation of the cuticle. Furthermore, this modified method allowed for the preparation of large areas of leaf. While this procedure may not be suitable for all cuticles, it is offered here as an easy and gentle method for preparing extremely delicate conifer cuticles that are destroyed by other chemicals and protocols.
conifer cuticle, cuticle preparation, cuticular analysis, fossil cuticle, palaeobotanical method, sodium hypochlorite
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.
Clarkia local flora, Columbia River Basalt Group, fossil aquatic macroflora, fossil aquatic macrophyte, leaf fossil, Miocene Climatic Optimum, Nymphaeaceae, Nymphaeales, plant taphonomy, Wanapum Formation