The morphological classification of trace fossils (as the term suggests) is based of only morphological patterns. This classification is based on Książkiewicz (1977) who arranged trace fossils from flysch deposits in the following manner. He distinguished 10 morphological groups. Each name of these groups is self-explanatory and the classification system therefore easy to apply. So I guess, we can do without additional text here... Another advantage is that this system is not based on any interpretational criteria and in contrast to the ethological classification based on Seilacher (1953) sharp borderlines can be drawn between the single groups. The disadvantage of this classification is that certain groups may contain very different ichnotaxa. Vertical traces are not represented in a own group. Uchman 1998 critisised that many ichnotaxa classified by Książkiewicz (1977) as “simple structures” actually are branching and therefore combined the groups “simple structures” and “branched structures”. Some ichnogenera exhibit a huge morphological variety in preservation. Depending on their preservation some of these taphonomic variants could easily be classified in different groups although they are the same. In the following the revised morphological classification by Uchman 1998 is reproduced, which is based on the system established by Książkiewicz (1977).
- Circular or elliptical structures
hypichnial or epichnial trace fossils with a circular or elliptical outline
- Simple and branched structures
Combination of the two groups “simple structures” and “branched structures” by Uchman 1998. Cylindrical, straight to slightly curved burrows. Wall may be smooth or structured with e.g. striae or incisions. Burrows may be short or long without termionable endings. The burrows may branch. Whether they branch horizontally or vertically does not matter. The branching however, does not produce a tight net- or boxwork (see point 8 below)
- Radial structures
...or rosette-like structures exhibit shapes similar to stars. Trace fossils my occur in hypichnial or epichnial preservation.
Although Książkiewicz (1977) only mentioned trace fossils having a horizontal or corkscrew-like Spreite, biogenic structures with a vertical Spreite should be included here.
- Winding and meandering structures
Combination of the two groups ”winding structures” and ”meandering structures” by Uchman 1995 because borders between winding and meandering cannot be drawn. Structures showing repeatedly, stretched curves (“winding”) or tight curves that may touch each other (meandering).
Structures having a planspiral coiling (Książkiewicz (1977)). However, traces having a vertical or even three dimensional coiling should be placed here as well in my opinion.
- Branched winding and meandering structures
Winding or meandering trace fossils that possess branches or short or long appendages. The branching might connect to other parts of the burrow, but these connections are exceptions. No regular net- or boxwork is being formed. According to Książkiewicz (1977) all trace fossils belonging to that group are hypichnial. However, his classification system was based on trace fossils from a flysch formation in Poland, so other preservations might occur elsewhere.
- Net- and boxworks
Burrows with more or less regular branching belong to this category. Most of the branches connect to other parts of the burrow. It does not matter if the branches only occurs in one plane (forming a network) or is three-dimensional (forming a boxwork).
A similar approach for classifying trace fossils has been published by Knaust (2012) although under different premisses. His main goal was to create a flow chart-like key for determining trace fossils on ichnogeneric level based on ichnotaxobases. A more detailed description of his approach you will find in the section “Ichnotaxa Database” of this home page.