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In-Depth Information
see
Uchman, 1995
). This procedure is not very favorable in order to delineate
contrasting behavior of the tracemaker, which in this case would probably be
dwelling
versus
feeding. In contrast, a number of unbranched meniscate burrows
are now differentiated at the ichnogenus level basically by the kind and organi-
zation of their backfill (
Smith et al., 2008
), corresponding to a smaller rank of
ichnotaxobases compared with the current concept of
Ophiomorpha
.
3. A NEWLY PROPOSED NOMENCLATURE KEY
3.1 Purpose and Advantages
In this chapter, a nomenclature key to the main ichnogenera is proposed, based
on a hierarchy of diagnostic features (ichnotaxobases). The purpose of this ich-
nosystematic classification is the organization of key ichnotaxa with respect to
their ichnotaxobases. The nomenclature key allows for the determination of
major groups of trace fossils down to the ichnogenus level. Although the pro-
posed classification certainly has weaknesses such as the subjectively selected
ichnotaxobases and their hierarchical order, partly inaccurate assignments, and
missing ichnogenera, it may serve as a basis for further evaluation and has the
following potential:
1.
It is the first compilation of valid invertebrate trace fossils at the ichnogenus
level since the publication of the
Trace Fossils
part of the
Treatise of Inver-
tebrate Paleontology
by
H¨ntzschel (1975)
. This overview of available ich-
nogenera could be the basis for an updated version of the
Treatise
.
2.
It guides the identification of synonymous or established ichnotaxa when
planning new descriptions or revisions. Examples of potential subjective
synonyms include
Akinereites
and
Nereites
,
Catenarichnus
and
Catenich-
nus
,
Cornulatichnus
and
Lithoplaision
,
Digitichnus
and
Cylindricum
,
Fimbrichnium
and
Psammichnites
,
Furculosus
and
Hoplichnus
,
Katbergia
and
Katarrhedrites
,
Ophioichnus
and
Zhadaichnus
,
Ovatiichnum
and
Ptycho-
plasma
,
Ramosichnus
and
Arborichnus
,
Sphaerichnus
and
Sabiuracolites
,
and
Tursia
and
Paradictyodora
.
3.
The nomenclature key facilitates the assessment of the deployed ichno-
taxobases for certain trace-fossil groups (e.g., ichnofamilies, ichnogenera).
4.
The classification scheme is intended to be an open document, which in the
future may be transformed into a digital database. In this way, it can be
continuously updated, improved, and extended in terms of ichnospecies,
geological ages, key references, figures, locality information, etc.
5.
Finally, this approach hopefully stimulates further reviews of remaining
groups of trace fossils.
3.2 Structure of the Key and Challenges
A major uncertainty exists in the definition of “trace fossils”, and workers
diverge concerning which groups are to be included. The key deals with the
main groups of trace fossils, for example, burrows, bioerosional trace fossils,
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