Ichnotaxonomy: Finding Patterns in a Welter of Information - Trace Fossils as Indicators of Sedimentary Environments - page 61

A few problems remained. What constitutes a trace? What is a fossil? What
about the activity of plants? These areas are still open to interpretation by any
taxonomist, but the consensus of the first two Workshops on Ichnotaxonomy
( Bertling et al., 2006 ) is the new starting point for any further discussion.
Bertling et al. (2006) recognized that many kinds of organismal behavior are
reflected in the fossil record, but not all should be named. For example, soils
are made by the collective behavior of many species of plants, animals, and
microbes, but it seems counterproductive to give these behavioral complexes
Linnaean names. Likewise, human artifacts are undoubtedly traces, but anthro-
pologists and archeologists already have their own systems of classification that
would only be hampered by the bestowal of Linnaean names to such items as
stone tools. The consensus of the two workshops on “What is a trace?” is sum-
marized in Table 2 .
The status of trace fossils that are interpreted to have been made by plants,
such as root traces, is unsatisfactory as the ICZN deals only with the “work of
animals”, not of members of other kingdoms. The status of reaction tissues, such
as galls grown by plants in reaction to the activity of wasps, is also unsettled. For
the time being, I would encourage researchers to name these fossils as if they
were unchallenged trace fossils. They can be sorted out later.
The question of what is a fossil constitutes another gray area, and one that is
ultimately unanswerable. Bertling et al. (2006) wrestled with this problem and
concluded that, in general, pre-Holocene material should be considered as fossil
while Holocene material should not. Even this distinction proved to be too sharp
for some researchers. Nielsen et al. (2003) pointed out that their deep-sea

TABLE 2 Categories of Fossils that are Considered as Traces for the Purpose

of Binominal Nomenclature. Modified from Bertling et al. (2006 )

Classified as traces under the ICZN Not classified as traces under the ICZN

Footprints, trackways
Trails
Burrows
Borings
Coprolites
Gastroliths
Regurgitaliths
Nests
Spider webs
Woven cocoons
Caddisfly cases
“Sand reefs”
Bite and gnaw structures, other signs of
predation
Signs of human biological activity

Skeletons, other hard parts
Soft tissues
Hair, feathers
Eggs
Calculi
Pearls
Embedment structures
Secreted cocoons
Plant reaction tissues (e.g., to insects)
Soils
Stromatolites
Pathological structures (signs of disease)
Signs of human technological activity