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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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