How To Identify Fossils

How to Identify Fossil Plants and Name New Species

Description reprinted with permission from Burke Museum of Natural History and Culture

What is it? Is one of the tougher questions that paleobotanists try to answer. There are nearly 300,000 species of living plants, and land plants are known as far back as the Silurian so there must have been millions of species that are now extinct. The typical botanical fossil is just a portion of the whole plant, a leaf, a cone, a piece of petrified wood, or maybe a pollen grain. Now there are two questions: What part of the plant is it? and What species did it come from?

It is hard to identify plants because they fall apart as they live, many parts look alike and may not preserve diagnostic details, and the quality of preservation may not be good enough to display the diagnostic details. Nonetheless, certain plant parts do have very diagnostic shapes and structures that allow them to be differentiated from other plants. The vein patterns of leaves, like human fingerprints, are a good example of plant morphology that has the potential to be useful in identification.

Traditionally, paleobotanists have described plant parts as biological species. For example, many of the fossils from the Green River Formation are identified only on the basis of fossil leaves with little or no knowledge of the rest of the plant.

In order to formally name a new species, the fossil that represents the new species is designated as the type specimen (also known as the holotype) and is placed in a museum or repository where it will be available indefinitely for researchers. A photograph and description of the morphology or anatomy of the new species is published in a scientific journal. Ideally, the author will analyze features of the fossil and determine how it fits into the tree of life and to which botanical family it belongs. Once published, the name is valid. This can be a very time-consuming process since the scientist must be satisfied that the species is unique and previously unknown, something that can only be known by an exhaustive search of the previously published literature.

The scientific name consists of two words, the first is the genus and the second the species. Together these are known as a binomial. Traditionally, only the genus is capitalized but both words are underlined or italicized (for example: Acer rubrum). Often you will see a person’s last name after the binomial. This is the author, the person who first published the species (for example Aralia wyomingensis Knowlton and Cockerell). When a later scientist determines that an earlier worker had placed a species in the wrong genus, he can recombine the name and his name is added to the list and the earlier author’s name is placed in parentheses.  For example, Macginitiea wyomingensis (Knowlton and Cockerell) Manchester. In this way, the presentation of the name tracks the original species and its history of reassignment.

This system was first standardized by a Swedish scientist named Linnaeus and we now refer to the naming system as the Linnaean System. This system is recognized by the World’s scientists and for the Botanical part of the Linnaean System, there is a book of formal rules known as the Code of Botanical Nomenclature.  

So when you ask the question, What is it? You are really asking, has this fossil been previously described and identified and what binomial does it have? To answer the question, you must therefore be able to see diagnostic features in the unknown fossil and then compare it to all previously described fossils. This can be brutally cumbersome since this means looking at many publications and the type specimens of interest are often in different and distant museums. To make this process easier, we use a technique known as Morphotyping.