Methodology (1): Supporting information
Although this paper is written as a general introduction, it is nevertheless helpful to illustrate some of the discussion below by reference to particular examples. Although we focus on the echinoids (Table 1), they are only illustrative; the recommended methodology is applicable to other palaeontological taxa. First and foremost, taxonomic publications concerning animals or plants must conform to the laws laid down in the International Code of Zoological Nomenclature (1999) or Greuter et al. (2000), respectively. A new taxon has to have a detailed, accurate description and (at least) adequate figures. A proper sequence in the description of new taxa would include the following sections, with related sub-headings.
Taxonomy – Each first description of a taxon in a published work has the taxonomy given in full, with subsequent related taxa requiring only the parts that differ. This saves space in the publication, something which journal publishers, editors and readers appreciate. For example (following the classification of Smith & Wright, 1989):-
Class Echinoidea Leske, 1778
Order Cidaroida Claus, 1880
Family Cidarea Gray, 1825
Subfamily Psychocidarinae Ikeda, 1935
Genus Tylocidaris Pomel, 1883
Subgenus Tylocidaris Pomel, 1883
[Species] Tylocidaris (Tylocidaris) clavigera (Mantell, 1822)
The author is included with the date of the first description, ensuring that readers are aware of the taxonomic priorities. This also helps with the identification of references in the bibliography. The first citation of any species in the text should be associated with the name of the author(s) and date of publication, which are treated as references and will appear in the reference list (Kelt & Palma, 1992). Within the body of the text the genus (and, if so subdivided, subgenus) can be reduced to the capital letter T. only - T. (T.) clavigera - except at the start of a sentence. The author can at this stage be omitted. The next taxon within the cidarids might then be:
Subfamily Cidarinae Gray, 1825
Genus Prionocidaris A. Agassiz, 1863
This avoids repeating the higher taxonomy (class, order, family), which is the same for both genera. Bengtson (1988) provided much sensible advice regarding the use and format of open nomenclature.
Synonymy list – This is a list that includes all previously published identifications and references to a given taxon. For example, the Chalk echinoid Gauthieria radiata (Sorignet, 1850) has been previously called:-
- Cyphosoma radiatum Sorignet, 1850 (this was the original designation)
- Cyphosoma subradiatum Sorignet, 1850 (originally perceived as a separate species, but subsequently synonymised)
- Phymosoma heberti Desor, 1858 (Desor thought differently)
- and several other designations until 1888 when Lambert erected the genus Gauthieria, with Gauthieria radiata (Sorignet, 1850) designated as the type species.
Synonymy lists can be exhaustive or selective; in the latter case, only the most notable references are listed. There are taxa whose complete synonymy lists would require a whole paper in themselves, such as the fossil bird Archaeopteryx. The preferred format of a synonymy list for Scripta Geologica should follow the style used by Taylor & McKinney (2006). For detailed comments on the construction of synonymy lists, see Matthews (1973).
Diagnosis – The diagnosis of a taxon is expressed in concise sentences which define the essential features of that taxon alone, using characters that are appropriate to the particular taxonomic level. No two species can have identical diagnoses. The diagnosis is a kind of shorthand whose purpose is to present all the salient characters for the taxon under consideration, whether species, genus or higher group. The amount of detail in the diagnosis will depend on the relevant characters present.
Etymology (derivatio nominis) – This gives the background to the name being given to the new taxon. This is useful to know, apart from the obvious interest, because it will help with the pronunciation of the taxonomic name, especially if given in honour or
Material – All of the specimens used in writing the description are listed, including the holotype or other primary types (see below), paratypes and other material. Under each category the following should be included:-
- details of the museum(s) or other repository where the specimens are kept;
- registration and/or accession number(s) of the specimen(s); and
- a brief description of the preservation of the specimen(s).
The name of the collection, collector and any other such details can be included, if appropriate. Type specimens are needed to define the species and may belong to a type series, a group of specimens used in the description of the species. This series can be conveniently divided into the primary type(s) (see below) and the paratypes. Technically, the primary type is the only specimen which can be called by the species name; all other such named specimens are merely compared with them. Assuming there has been no misidentification of the type specimen(s) (taxonomic and other complications arise when this happens), its species name never changes. Conversely, paratypes and non-type specimens which have been identified as one taxon can be re-named if they are re-identified as something else. Indeed, they may even become the basis for new species. The various forms of primary types are explained below (Davies, 1961; International Code of Zoological Nomenclature, 1999; Greuter et al., 2000).
- The holotype is the single reference specimen for a named species. When several specimens are used for a description, those apart from the holotype may be named paratypes. These are named as such by the author, who may also refer to any further specimens used as ‘other material,’ if appropriate. In earlier literature, paratypes may not have been designated as such and hence all other specimens used in such descriptions are regarded as paratypes.
- A syntype has the same status as a holotype. A syntype(s) is one or one of several specimens of a type series for which no holotype was designated. All the specimens used in that original description are syntypes.
- A lectotype is a specimen which is selected from syntypes, or from a paratype series in which the holotype was not defined or has been lost. It is the specimen which best represents the original concept of the species and has the same status as a holotype. The remaining syntypes (if any) are then referred to as paralectotypes.
- A neotype ('new type') is a specimen which is selected when the holotype is lost or unidentified within a collection and there are no recognised syntypes or paratypes. The neotype would be chosen from specimens which best represent the original concept of the species and has the same status as a holotype. Ideally it is chosen from specimens which came from the same locality and horizon as the original type. This may not always be possible, however, especially if the original locality was not known or is no longer accessible.
The term ‘type species’ (not to be confused with type specimen) is applied to the species which characterises a genus. For example, the type species of Hyposalenia is Salenia stellulata L. Agassiz, 1838, with several other species assigned to the genus Hyposalenia. The type species of Hyposalenia will never change, but the other species assigned to that genus can be placed in other genera if revisions occur.
Localities – The locality details of the type and other specimens are given so that the reader can, ideally, exactly identify the source site of the material. Do not assume that the reader will know where the locality is - some may even be uncertain of the country - so state the obvious, for example, “Barton-on-Sea, Hampshire, England” (as distinct from, for example, “Barton, Devon, England”). Locality maps show from where the material comes. It is a good idea to include not only a detailed map of a locality, but also a much larger scale map to show where it is in relation to elsewhere, such as the country of origin.
A locality is made up of several different components which can be broken down into smaller units, especially useful if the information is to be added to a database. The reason for doing this is for retrieval in a variety of forms (for example, a card index), and is particularly important for more advanced nested and other relational electronic databases. Conventionally, the information is given in order of increasing rank, closing with the country of origin. The latitude and longitude can be given when known, together with, or as an alternative to, the local national grid reference. This might be appropriate if copyright information for the grid reference is likely to be infringed or permission is difficult to obtain. The use of GPS information has greatly simplified determination of latitude and longitude.
Stratigraphy – As with locality details, in order that readers unfamiliar with the geological data being presented can find their way around the stratigraphy, do not assume that they are familiar with the stratigraphy; once again, state what to you may appear to be obvious. The stratigraphy is given in descending rank order, and breaks down the essential information into three main areas and progressively smaller units:-
- Chronostratigraphy deals with time alone - period, age, stage, etc.; for example, Cretaceous; Coniacian. It simply tells the reader how old the material is. There is no implication of what fossils are present, nor the rock types in which they were found. This is important information for readers who do not know the minutiae of the stratigraphy involved.
- Biostratigraphy deals with the details of where exactly in the geological column the fossils occur. Here are included the formal biozones and subzones which locate the fossils within their time bands, for example, Micraster cortestudinarium Biozone (or just Zone) (note that ‘Biozone’ and ‘Zone’ take a capital letter). Again, there is no implication of any rock types.
- Lithostratigraphy deals with the rocks themselves. Rock masses are divided into more manageable units in descending order - group, formation, member, bed, etc. The main groups have formal names, but the smallest units may only be known by their local or informal names.
Rawson et al. (2002) provided comprehensive advice on stratigraphic usage. The latest in the Cambridge series of geologic time scales was recently published (Gradstein et al., 2004). Shaw (1971) provided a succinct critique of the poor use of stratigraphic data in palaeontology.