Ichnotaxonomy: Finding Patterns in a Welter of Information - Trace Fossils as Indicators of Sedimentary Environments - page 69

Paleodictyon by Seilacher (1977, 2000) . There is no need to name ichnosubspe-
cies to reflect every slight difference found in material.

7.7 Exceptional Cases
In some cases, a strict adherence to rules is intolerable. For example, imagine a
researcher who rediscovers the type specimen of the type ichnospecies of a
common ichnogenus in a museum drawer, where it has lain unexamined for
a century and a half, and finds that it not only does not match the current con-
sensus of the diagnosis of that ichnogenus but is actually a plant. Following the
rules would lead to a situation where every specimen bearing a common name
would have to be renamed, while the single specimen to retain the name would
have no meaningful connection to the vast majority of the literature. The
International Code of Zoological Nomenclature (1999) allows for the resolution
of such exceptional cases by petitioning the Commission to overturn one or
more of its rules. The process is fairly lengthy and should not be considered
as a method of solving one researcher's distress, but of resolving a problem
of interest to the whole ichnological community.

7.8 Beyond Systematics
Part of the skill involved in taxonomy is knowing what aspect of it to use and
which to set aside. The strict systematic approach is most useful when one wants
to answer questions relating to particular trace fossils and the organisms that
made them. This is not restricted to questions such as “What made this sedimen-
tary structure?” Systematics is necessary, for instance, when one wishes to
understand the biodiversity represented by an assemblage of trace fossils. This
approach is also needed, generally speaking, when exact answers are wanted.
The other approaches promoted by Seilacher (1953) can be more appropri-
ate in cases where large datasets based on other criteria are used to determine
facies. The two facies approaches that are most in use are the studies of
archetypical ichnofacies ( Frey and Seilacher, 1980; MacEachern et al., 2007,
2012; Seilacher, 1963, 1964 ) and ichnofabrics ( Ekdale and Bromley, 1983 ).
The ichnofacies approach depends on the proportion of different ethological
categories, the Skolithos Ichnofacies being dominated by vertical dwelling
traces, the Nereites Ichnofacies by feeding traces, and so on. Although most ich-
nofacies work does utilize ichnotaxa, ichnofacies can be used in the absence of
identifiable ichnotaxa; for example, “dominance by vertical dwelling burrows”
is sufficient to determine that a stratum belongs to the Skolithos Ichnofacies
without identification of Skolithos, Diplocraterion, or other ichnotaxa.
The more flexible ichnofabric approach ( Ekdale and Bromley, 1983; Ekdale
et al., 2012; Gerard and Bromley, 2008; Taylor et al., 2002 ) uses repetitive,
observable characters of biogenic structures, without necessarily identifying
them systematically, to categorize the textures of rocks into different