Trace-Fossil Systematics - Trace Fossils as Indicators of Sedimentary Environments - page 92

The rules of the third edition of the International Code of Zoological
Nomenclature (ICZN), published in 1961 , regarded trace-fossil taxa established
after 1930 as to be not available. This fact seems to contradict the significant
upturn in the establishment of new ichnogenera around the same time, which
may be related to the first edition of the Treatise section on Invertebrate Trace
Fossils ( H¨ntzschel, 1962 ). New proposals for the ichnotaxonomical treatment
of ichnotaxa and their coverage under the ICZN during the 1970s led to a revi-
talization of ichnotaxonomical investigations ( Basan, 1979; Pemberton and
Frey, 1982 ). The second edition of the Treatise ( H¨ntzschel, 1975 ) provided
an excellent basis for further ichnotaxonomical work. In the 1970s, new ichno-
taxa were introduced from a mainly paleontological point of view, whereas
more recent descriptions are often related to more complex situations and a
sedimentological perspective.
An analysis of the established database reveals some interesting facts worth
mentioning. First of all, many new ichnogenera were introduced in the past few
decades following the rules of the ICZN. This is very welcome, as it helps to
provide a stable platform for communication and to make ichnotaxa available
for paleontological and sedimentological studies. Seventy percent of all inver-
tebrate trace fossils (at the ichnogenus level) included in this database was intro-
duced after the publication of the first edition of H¨ntzschel's Treatise in 1962.
As a result, many new forms were properly described, although the rapidly
increasing number of ichnotaxa would hamper their handling if no robust
classification scheme were provided.
A lot of good work was done to review different groups of trace fossils,
which in turn led to an increase of stability in ichnotaxonomy. This effort
has resulted in the relatively high status of many (mainly common) ichnogen-
era. Conversely, the ichnotaxonomical status of many less common ichnotaxa is
poor and diminishes their value for further use. This is often the case where new
ichnotaxa are introduced without an appropriate study of their morphological
features, relationship with other ichnotaxa, and potential synonyms.
Figure 8 displays a graph with the frequency of major trace-fossil groups as
regarded in this classification. Most of the analyzed ichnogenera are burrows
(60%), followed by bioerosional trace fossils (17%), trackways (14%), imprints
(5%), and trails (4%) (transitional formswithmultiplebehavior styleswere counted
in those groups where they are most common). It has long been a custom to name
ichnogenera with the suffix - ichnus , which applies to about 44% of them.

4. WAY FORWARD
The proposed nomenclatural key is intended to test applied ichnotaxobases,
existing trace-fossil groups, ichnofamilies, and ichnogenera for the classifica-
tion of trace fossils. If it succeeds, it may be the basis for the establishment of
further keys for other trace-fossil groups. In the short term, it may assist in the
review of existing ichnogenera and ichnofamilies and aid the proper description
of ichnotaxa,

leading toward a unified application of ichnotaxobases for