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distinction that was clarified by
Bromley (1970)
. Still another problem is that the
figures emphasize type material which is not always representative of the ichno-
genus as it is understood today, while other figures taken from significant articles
are neither type material nor representative; some indeed are no longer thought to
belong to the ichnotaxon in question. However, the main problem with
H¨ntzschel's compendium is simply that it is out of date: Many ichnogenera have
been named, emended, or clarified since 1975 (
Knaust, 2012
). The last problem
can be addressed, if tediously, by reference to the extensive bibliographies and
lists of new ichnotaxa in issues of the
Ichnology Newsletter, Biological Abstracts,
GeoRef, Zoological Record
, and other serials. A more rapid method may be to
consult an expert.
As pointed out previously, identification of ichnotaxa may require better
material than the researcher has at hand, and very often better material than
exists. Only well-preserved, distinctive material should be used as the basis
for new ichnospecies (
Bertling et al., 2006
).
The new name is commonly accompanied by a
diagnosis:
an account of the
characters that distinguish the new ichnospecies from all others. This is not a full
description but may consist of a selection of descriptive features. Alternatively, a
diagnosis may contrast the features found in the new material with those of pre-
viously known ichnotaxa. This is, however, less satisfying than a diagnosis
expressed in more positive terms. A diagnosis should be succinct and cover only
the essential characters, saving the remainder for a separate description.
An effective diagnosis uses the same kinds of characters as have been used
in the most similar previously described ichnotaxa. These kinds of characters
are called
ichnotaxobases
. When ichnotaxonomists meet, the proper selection
of ichnotaxobases is likely to take up a good deal of their time. At present, the
best summaries of ichnotaxobases for invertebrate burrows are those of
Bromley (1996)
and
Bertling (2007)
; for invertebrate borings, consult
Bromley (1970)
and
Kelly and Bromley (1984)
.
Not all of the description of a trace fossil is used in the diagnosis. In an ich-
notaxonomic work, the diagnosis is ordinarily followed by a separate
descrip-
tion
section that includes features that are not considered to be crucial to the
naming of the trace fossil, but nonetheless have their own significance. Good
descriptions last forever: The names and interpretations that
Brongniart
(1828-1838)
gave to trace fossils are no longer current, but his illustrations
and descriptions are still useful after nearly 180 years. Poor descriptions are
usually forgotten except when they are attached to new names; so, it is partic-
ularly important to get it right the first time.
7.5 Ichnofamilies and higher Ichnotaxa
Biologists classify living and fossil organisms into a hierarchy of many addi-
tional ranks, extending beyond species and genera: families, orders, classes,
phyla (in botany,
divisions
), and kingdoms. But all life has a shared ancestry
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