The Basics of Classification

When different types of fossils are talked or written about, they are often given complicated Latin names, such as Dactylioceras commune, Neohibolites minimus and Stigmaria ficoides. These names can sound a bit daunting and you may think that they are more complicated than the need to be, but there are reasons why we use Latin and also why we use two names.

Why use Latin?

We use Latin names primarily because it is very useful for everyone around the world to call the same fossil or extant species by the same name. If every language had a different name for each species, things would be very complicated. So everyone uses Latin, as that is what scientists have been doing for hundreds of years.

Why use Two Names?

The two names that we use refer to a fossil’s genus and its species. When used together, the two-piece name identifies one specific type of fossil.

One genus may have many species. For instance, the ammonite genus Euhoplites has over 15 species, for example, Euhoplites nitidus, Euhoplites lautus and Euhoplites proboscideus.

Also, more than one genus can have a species of the same name, for example, Palaeaspis bowerbanki (a turtle), Hemiaster bowerbanki (a starfish) and Pycnodus bowerbanki (a fish). When this happens, it is usually because they are named after an eminent scientist, in this case, after James Scott Bowerbank, who was a British geologist (1854-1866).

The bigger picture

These genus and species names are the tail end of a larger classification system, which gives every organism – both living and fossilised – its own unique place in the order of things.

The Hierarchy of Classification

There are seven levels in the standard system of classification. These are:

Kingdom – The most basic level of classification. Scientists have varying views of how many (that is, five or six) kingdoms of life there are, but when dealing with fossils, generally only the plant (Plantae) and animal (Animalia) kingdoms are encountered. However, you may come across one other kingdom – the Protista (single celled organisms) – should you ever deal with microfossils, in particular, forams.

Phylum/Division – In the case of animals, the phylum of a specimen tells us something about its internal body make-up. Animal phyla include the Chordates (animals with a backbone) and the Echinoderms (marine animals with a general five planed symmetry, for example, crinoids, starfish and sea urchins). In the case of plants, the word ‘division’ tends to be used rather than ‘phylum’.

Class – After an organism’s phylum comes its class. For instance, among the Chordata, there are numerous classes, including the birds (Aves), the mammals (Mammalia) and the reptiles (Reptilia). All of these have back-bones, but are different in many ways.

Order – This subdivides a class. For instance, the order Mammalia includes primates (man, gibbons, lemurs etc), rodents (rats, mice, bats etc) and the cetaceans (whales, dolphins etc). All of these Mammalian orders share the fact that they give birth to live young, have hair and are warm blooded, but they also have very obvious differences – a whale looks and acts nothing like a person.

Family – This subdivides an order. For instance, the Primate order includes the Hominidae family, which is made up of humans and the great apes.

Genus – This is a fairly specific level of classification, where, usually clear similarities can be seen between the various genera of the same family (for example, the Hoplitidae family of ammonites, which includes the Hoplites, Anahoplites and Euhoplites genera).

Species – The species level of classification is the most specific when used in conjunction with the genus. There are very clear similarities between different species of the same genus. For instance, the various species of the Dactylioceras ammonite genus (for example, Dactylioceras commune, Dactylioceras tennuicostatum and Dactylioceras semicelatum) all look very similar. In fact, it can often be quite hard to identify a fossil to this specific level.

Writing Scientifically

There are a few rules to remember when writing about different types of fossils. Some of the main ones are set out below:

  • Always write genus and species names in italics.
  • When writing the genus and species name, the genus name always has a capitalised first letter, whereas the species name always starts with a lower case letter.
  • If you are unsure of which species of a certain genus you have, you can write down just the genus and add ‘sp.’ Afterwards, for example, Hysteroceras However, note that the ‘sp’ is not in italics as it does not form part of the name.

If you are writing about a few different species of the same genus and you are not also writing about another genus that starts with the same letter, you can shorten the genus name to just its first letter once you have written it out in full, for example, by referring to Dactylioceras ammonites as D. tennuicostatum and D. semicelatum.

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