Cuticular analysis – an assistant in paleontological research

Cuticular analysis is a specific, systematic approach for investigating the cellular structure of leaf epidermis. The cuticle is a protective waxy layer secreted by the epidermis into which the cells of the leaf are ‘imprinted’. This analysis can also be successfully applied to the fossil leaves of plants, especially woody plants. In contemporary science, this method forms one of the components of palaeobotanical research on fossil leaves. It is an invaluable aid in determining taxonomic relationships within the plant system.

In the research described in the scientific journal, samples from the end of the 19th century stored in the collections of the National Museum in Horní Počernice were used. These were collected in Lidice near Slaný and other Central Bohemian localities and described and published by Josef Velenovský, a world-renowned Czech botanist and paleobotanist. In addition to the revision of these historical samples, new findings from the Pecínov quarry near Nové Strašecí were described. All the material comes from the Peruc-Korycany Formation of the middle Cenomanian.

Fig.1: Map of the Czech Republic indicating the location of the Pecínov quarry within the Cretaceous sediments (grey). Figure from the article.

The most exciting aspect of Jana Čepičková’s and Jiří Kvaček’s work is undoubtedly the definition and description of the new genus and species of foliage Ascarinophyllum pecinovense, named after the Pecínov quarry which solely due to the owner's willingness provides unique finds, not only of fossil flora. The type collection of this genus and species is also kept in the depositories of the National Museum in Horní Počernice. The specimen is well preserved which meant it could be examined using cuticular analysis. Consequently, the structures of the leaf surface, such as stomates and veins, were identified in detail.

In addition to the description of a new genus or species, the researchers dealt with a possible change in the position of the species Banksites saportanus within the plant system. The development of scientific knowledge since the Austro-Hungarian Empire assisted them with this shift. Josef Velenovský, a talented scientist in the days when his research was conducted, could not have classified the prints of the leaves more correctly. It was only after further discoveries and research in the ensuing decades that scientists could correctly paste the fossil into the plant system. This resulted in a new taxon combination, Todziaphyllum saportanum (Velen.) Čepičková et J. Kvaček, comb. nov. In the nomenclature of plants, the brackets indicate the author of the original valid definition of the taxon, the so-called basionym. Following the brackets are the authors who assigned the plant fossil to another genus in a new and more correct way. Comb. nov. at the end of the taxon name is an abbreviation of the Latin words combinatio nova which means the actual reassignment of an original taxon already published.

Fig.2: Abaxial cuticula (from the underside of the leaf), inner surface, holoparacyte stomata (Jana Čepičková, collection of the National Museum).

Scientific knowledge undergoes constant development and, owing to the work of research pioneers, it can constantly move forward. Today, using modern methodological approaches, such development is possible. This is why it will still be possible to push the boundaries of human knowledge in the future. This will allow humans, who are by nature curious creatures, to use the knowledge acquired to understand better the workings of the world.

Jana Čepičková, and Jiří Kvaček. "Fossil leaves of Cenomanian basal angiosperms from the Peruc-Korycany Formation, Czechia, central Europe" Review of Palaeobotany and Palynology, Volume 309, (2023), 104802. doi: 10.1016/j.revpalbo.2022.104802.

Jan Geist