Julia Gravendyck1, Patrick S. Herendeen2, Robert A. Fensome3, Martin J. Head4, Jiří Kvaček5, James B. Riding6
1 Plant Biodiversity Section, Bonn Institute for Organismic Biology, University of Bonn, Bonn, Germany
2 Chicago Botanic Garden, Glencoe, IL, USA
3 Natural Resources Canada, Geological Survey of Canada (Atlantic), Dartmouth, NS, Canada
4 Department of Earth Sciences, Brock University, St. Catharines, ON, Canada
5 National Museum Prague, Prague, Czechia
6 British Geological Survey, Nottingham, UK
Introduction
The Madrid Code (hereafter ‘Code’), the latest edition of the International Code of Nomenclature for algae, fungi, and plants (Turland et al. 2025), introduced several new rules to address the particular requirements for fossils (Turland 2025).
One challenge we often face is locating the type specimen of a previously described fossil-taxon, especially for microfossils such as pollen, spores and dinoflagellate cysts. Reference to types, allowing their restudy, is an essential component of taxonomic research. Previous studies have illustrated how challenging it can be to find a specimen in the absence of adequate information that facilitates its relocation (Gravendyck 2021; Gravendyck et al. 2021, 2022, 2023). Consequently, a new rule was introduced in the Code, among other rules and recommendations, to improve the definition, utility, and curation of type specimens:
Art. 40.8. “For the name of a new fossil-species or infraspecific fossil-taxon published on or after 1 January 2026, the protologue must clearly indicate where the holotype specimen (see Art. 8.6) is located within the rock, sediment, or preparation.”
The aim of this rule is to facilitate relocation of type specimens for future study. In stating “where the holotype specimen (see Art. 8.6) is located within the rock, sediment, or preparation” the focus is on the provision of all necessary information that facilitates finding the specimen. It is already standard scientific practice to provide collection numbers and indicate the location of the specimen when it co-occurs in a mixed preparation such as a palynological strew mount or in a rock sample with multiple macrofossils. Art. 40.8 makes the provision of this information a prerequisite for valid publication of a new name. While the rule is particularly important for microfossils, it pertains to all fossils.
The purpose of this short note, and a more detailed article in preparation, is to make the palaeobotanical and palynological communities aware of the new rule, and to explain briefly how it can be met.
What is a ‘protologue’?
A fundamental concept in the Code is the protologue. The Code and its glossary define the protologue as “everything associated with a name at its valid publication, e.g. description, diagnosis, illustrations, photographs of habitat, references, synonymy, geographical data, citation of specimens, discussion, and comments” (Art. 6.13 footnote). Accordingly, the information required by Art. 40.8, this being the location of the holotype within the rock, sediment, or preparation, must be included in the content accompanying the original description. In practice, this is usually achieved by providing information on the kind of fossil and its preparation (e.g. compression fossil, isolated mesofossil, cuticle preparation, palynological strew mount) and the accompanying collection information (e.g. collection number) as well as overview images of the type specimen together with explicit metadata or comments specifying its exact position.
For different kinds of fossils, the practices described below illustrate a selection of possibilities for putting this into practice. However, with equipment and techniques ever progressing, there are and likely will be many ways to “clearly indicate” the necessary information that allows the holotype specimen to be relocated within the rock, sediment, or preparation.
Microfossils (palynomorphs)
The least ambiguous way to relocate a single palynomorph is a single grain mount on a microscope slide (Riding 2021, p. 51–53). The information that it is a single grain preparation in combination with a slide or museum collection number clearly indicates where the palynomorph is located in the preparation. To make relocation straightforward, the specimen could be circled using an engraver or permanent ink, although ink markings on a polished glass surface are susceptible to degradation.
However, most palynomorph taxa are described from strew mounts on microscope slides used for routine observation and counting. In such mounts, the admixture of many thousands of grains can substantially hinder the relocation of a single specimen. A common and easy relocation method for strew mounts is the use of an England Finder (Riding 2021, p. 92–93; Gravendyck et al. 2021, 2022), which is a standardized coordinate grid etched or printed onto a microscope slide. The location within the grid square facilitates the unambiguous relocation of a single specimen (e.g. C12/4) (Graticules Ltd. 1962). Gonzalez (2012) described a method for digitally converting microscope stage coordinates into England Finder references.
Before the availability of the England Finder, palynologists used several other methods involving self-made grids or ink-markings on the slide (Riding 2021, supplementary data appendix 7.6). Many of these options are still helpful if an England Finder is unavailable or in cases where the slide in question is different in size to the England Finder. Physical marking using permanent ink rings or dots can be used to clearly indicate the position of a palynomorph (Riding 2021, fig. 58). When multiple specimens are designated as types on the same slide, ink circles around the specimens in question can serve in the same way. In comparison to the relatively expensive England Finder slide, the marking ethod is quick, cheap, and sufficiently precise if conducted with care. However, even “permanent” ink can be degraded or erased when removing immersion oil from a microscope coverslip, so great care needs to be exercised. If a high-resolution digital scan of a slide with a type specimen can be undertaken, the location of individual specimens can easily be permanently recorded (Jaramillo et al. 2025).
Accordingly, the Code recommends the following: “if a type specimen is prepared on a microscope slide, it is strongly recommended that the position of the specimen be indicated by an England Finder reference […] or equivalent unambiguous reference (e.g. single-grain mounts or permanent ink circling […]) to facilitate finding it again.” (Recommendation 8A.5). Following this recommendation thus clearly satisfies the unambiguous relocation of specimens on microscope slides required in Art. 40.8.
Type specimens are rarely designated from SEM stubs in palynology, but in such cases the author should either use a grid system to indicate a location (e.g. Laing 1974, Zippi 1991) or document the stub number and location on the stub in another way to relocate the specimen. Another option for strew preparations on SEM stubs is to provide a digital overview scan of the stub with a marker to indicate the location of the type specimen. These methods can thus satisfy the necessity for location indication required in Art. 40.8.
Mesofossils (e.g. fruits, seeds etc.)
If a single mesofossil is mounted on an SEM stub, specification of the SEM stub identification number alone is sufficient to satisfy Art. 40.8. If multiple specimens are mounted on a single stub, Art. 40.8 is satisfied only if the protologue explicitly distinguishes the holotype from other specimens on the stub. For dispersed or disaggregated mesofossils stored in Petri dishes or other containers, Art. 40.8 can be satisfied by clearly labelling the storage container. In addition, the protologue should explicitly state that the specimen was removed from the original sample and is preserved as a single preparation and must cite the corresponding collection number under which this preparation is now curated.
Macrofossils
Macrofossils, such as leaf compressions preserved on a piece of rock or as inclusions in amber, are straightforward if only one fossil is present on the sample. Labelling with a catalog number, which is cited in the protologue, is standard practice. If multiple fossils are present on a rock sample, then some method of labelling the individual fossils is needed, along with an indication of the type specimen, ideally on the rock and in the figure caption in the protologue depicting the type specimen. One solution here is to firmly affix an annotated label with an arrow indicating the type specimen using water-insoluble glue.
Cuticle or pollen preparations prepared from macrofossils or mesofossils should be labelled with the same collection or catalog number as the type and ideally stored in the same collection as the type material. If the preparations of the type specimen are stored in a separate collection (or institution), this fact should be mentioned in the protologue and the preparations should be adequately labelled.
Permineralized wood is usually documented through preparation of multiple thin-section slides from the specimen. Thus a new taxon based on a fossil wood specimen is almost always represented by one or more pieces of wood plus multiple anatomical thin section slides. The publication should provide clear indication of all the preparations and remaining materials that correspond to the type specimen, including their reference or collection numbers.
Anatomically preserved fossils in a coal ball or chert, for example, are often comingled with material from other taxa. They can be labelled much like macrofossils, although they may require more detailed labelling to indicate the type specimen. A specimen preserved in a coal ball is likely to be represented by multiple preparations and isolated pieces of the coal ball or acetate peels (Galtier and Phillips 1999). Information on the slides and/or collection numbers and location of these preparations, which all represent the holotype specimen, must be provided in the protologue, a practice that is already standard.
What if there is an “error” in the location information or if the preparation is altered?
Authors should of course make every effort to provide accurate details that are necessary for future workers to locate the type material, a critical need for future taxonomic research. The Code makes allowances for some kinds of inadvertent errors in the protologue (e.g., Art. 6.14, 9.10, 9.24, 23.5, 40.4, 41.3, 41.6, 41.8), and in these cases the error does not invalidate a nomenclatural act. However, omissions of required information are not forgiven, and the nomenclatural act is not validly published.
A common problem in palynology is that microscope slide preparations degrade or become altered through time, such as the palynomorph moving, the mountant drying out, or the cover slip detaching (Gravendyck et al. 2021). Similarly other types of collections may alter over time, either intentionally or unintentionally. We cannot anticipate all these eventualities, and they do not invalidate a nomenclatural act.
Summary
The intent of the new Article 40.8 is to make the relocation of type material easier for future researchers. While the wording of the Article may appear onerous or seem unnecessary, experience has shown that type material is commonly difficult to relocate, hindering new research. It is already standard practice for necessary specimen location details to be documented in the protologue. Art. 40.8 emphasizes as a requirement the need for this information to be well documented.
Madrid Code
The Madrid Code is freely available online through the International Association for Plant Taxonomy (IAPT) website. https://www.iaptglobal.org/_functions/code/madrid
References
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