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131
Hunt et al., eds., 2012, Vertebrate Coprolites. New Mexico Museum of Natural History and Science, Bulletin 57.
DIGESTICHNIA (VIALOV, 1972) – AN ALMOST FORGOTTEN
ETHOLOGICAL CLASS FOR TRACE FOSSILS
LOTHAR H. VALLON
Geomuseum Faxe (Østsjællands Museum), Østervej 2, DK-4640 Faxe, Denmark; e-mail: kv@oesm.dk
Abstract—The new ethological class Digestichnia is introduced in the present article. It comprises all trace fossils
(and their recent counterparts) originating from the digestive process of animals, such as coprolites (feces),
regurgitalites (regurgitations) and gastroliths. The class is based upon a group within the unused classification
system for trace fossils proposed by Vialov in 1972.
INTRODUCTION
For coprolites of all kinds (including cololites sensu Hunt, 1992),
the ethological class Faecichnia was informally introduced in the
‘Skolithos’-Internet-forum in 2002 (e.g., http://listserv.rediris.es/cgi-bin/
wa?A2=ind0211&L=SKOLITHOS&F=&S=&P=5116). This term ob-
viously was created by several parties independent of each other, but
was never formally erected (M. Bertling, personal commun., 2010). Re-
cently, the term was utilized by Patel and Desai (2009), who introduced
the Faecichnia-ichnocoenosis for pellet-dominated environments that
were produced by the reworking of the surface layers of matgrounds by
crustaceans and polychaetes in sand-dominated tidal areas.
In any case, the term Faecichnia unfortunately does not encom-
pass all the processes that may occur during digestion. Hence, regurgita-
tions and gastroliths are not covered by this term, and its use as an
ethological class is therefore not recommended. However, Vialov (1972)
introduced the class-like category “Digestisignia,” comprising all kinds
of traces left by digestion, including feces, regurgitations and gastroliths.
Unfortunately, his system of trace fossil classification was too detailed
(see below) and therefore rather impractical, which is why it was neither
taken over by Western nor Eastern scientists. Thus, the term has not
been used in the last few decades. The following article draws attention
to this forgotten class-like category by providing it with a proper defini-
tion, and by renaming it according to modern standards as Digestichnia
(after Seilacher, 1953; cf. Bromley, 1996).
THE CLASSIFICATION SYSTEM OF VIALOV (1972)
The first comprehensive classification system for trace fossils
was presented by Seilacher in 1953, who divided trace fossils according
to the behavior of the tracemaker at the moment the trace was created.
Nowadays, his system of ethological classes is widely accepted. Several
authors tried to extend this system by adding or dividing classes (e.g.,
Müller, 1962). However, most of these classes or class-subdivisions
were not accepted in the years following their publication. The latest
published scheme for animal behavior by Bromley (1996) has seven
ethological classes in addition to the original five given by Seilacher
(1953). Later additions to that scheme are the Fixichnia by Gibert et al.
(2004) for attachment traces and, more recently, the Mortichnia by
Seilacher (2007) for traces that were produced during a death struggle.
In 1972, Vialov published a detailed classification system for trace
fossils, mainly as an extension of the Seilacherian system. In contrast to
the much more practical ethological approach by Seilacher (1953), Vialov
(1972) distinguished between “Vivichnia” and “Vivisignia.” He defined
his “Vivichnia” as “physical traces left by the body or extremities of the
[living] animal” and his “Vivisignia” as “traces, or more precisely, signs
[and their remains] of physiological activity” by an animal. Further sub-
divisions were made for these two categories according to the tracemaker’s
taxonomy (vertebrates or invertebrates), and the purpose of the trace or
the tracemaker’s behavior while producing it. In the fossil record these
criteria are not always determinable, so many trace fossils could not be
placed in Vialov’s system.
Translated into the ethological system based on Seilacher (1953),
the “Vivichnia” sensu Vialov (1972) mainly comprise Repichnia (includ-
ing all movement traces), Aedificichnia and Domichnia. The “Vivisignia”
on the other hand, include all kinds of traces produced by the body
functions of the tracemaker. Most of these “Vivisignia” categories (signs
of growth, illnesses and injuries) were later excluded from consideration
as trace fossils by Bertling et al. (2006). However, the class-like category
of the “Digestisignia” matches the requirements for trace fossils given by
Bertling et al. (2006) and is characterized and renamed in the following as
the ethological class “Digestichnia” to be etymologically consistent with
the Seilacherian system.
DIGESTICHNIA (VIALOV, 1972)
The above mentioned complexity, impracticality and the fact that
Vialov failed to publish it in a widely distributed journal (it was only
published as a conference abstract) led to the classification system being
essentially ignored and eventually being buried in oblivion. Nevertheless,
traces of digestion are common in the fossil record in terrestrial as well as
in marine environments (see this volume) and have to be included in the
widely accepted system of animal behavior based on Seilacher (1953).
Regardless whether produced by invertebrates or vertebrates, fossil
remains from the digestive systems, such as coprolites (including
cololites), regurgitalites, gastroliths, etc. have to be regarded as trace
fossils (cf. Abel, 1935; Hunt, 1992; Bertling et al., 2006). Following
Bertling et al. (2006), trace fossils are morphologically reoccurring struc-
tures that result from the live activity of an individual organism or homo-
typic organisms modifying a substrate. For coprolites and regurgitalites
the modified substrate consists of more or less (semi-) digested food and
food parts (cf. Bertling et al., 2006). Gastroliths, on the other hand, are
substrate stones or stone-like concretions that have been modified by in-
stomach digestive action and therefore show abrasion and etching caused
by rhythmic muscular contractions of the gizzard, stomach acids and
enzymes (cf. Bertling et al., 2006, cf. Wings, 2004, 2007). It is not
important in this context whether these stones are ingested deliberately
or accidentally by the tracemaker or whether they were generated inside
the digestive organs (see below for discussion and explanation).
Coprolites of vertebrate or invertebrate origin (e.g., fecal pellets of
molluscs, brachiopods or arthropods) as well as other excretions leaving
the intestines at the distal end of an organism would be covered by the
informally introduced term Faecichnia (Skolithos-Internet-forum on trace
fossils: http://listserv.rediris.es/archives/skolithos.html 2002). But di-
gestion is much more complex. Especially, reptiles, birds and some fish,
but also some molluscs (e.g., cephalopods, suspension-feeding pelecy-
pods and gastropods) regurgitate undigestible parts such as bones, scales,
hair or parts of exoskeletons of their prey or accidentally ingested sedi-
ment particles (e.g., Petzold, 1959, 1967; Schäfer, 1962; Duke et al.,
1976; Andrews, 1990; Hockett, 1996; Bochenski et al., 1993; 1998;
Prins et al., 1991).
Documentation or scientific research on regurgitations of groups
other than birds is very scarce. However, on the basis of the published
literature and the examples from the fossil record, a definition of regurgi-
132
tations produced by vertebrates can be attempted: Fossil and Recent
vertebrate regurgitations are accumulations of disarticulated or partly
articulated, indigestible parts of prey animals (rarely also plants or fungi),
sometimes of various origins. These accumulations very often exhibit a
sharp boundary towards the surrounding sediment, which was caused
by the adhesive organic slime binding together the indigestible, regurgi-
tated parts.
Hard content, like bones or (parts of) exoskeletons, can be partly
fractured due to chewing and biting (Fig. 1) or dissolution by stomach
acids by the predator (Bochenski et al., 1993, 1998 and references to
different birds therein); it may also remain completely intact when the
prey was swallowed as one piece. In contrast to hard body parts found
in coprolites (cf. Fisher, 1981; Andrews and Fernández-Jalvo, 1998),
regurgitated material is bigger in size and articulated hard body parts
occur more often (Fig. 2; cf. Sanz et al., 2001). Fractured and unfractured
content of regurgitalites may show signs of etching by stomach-acids like
surface pitting (Hockett, 1996; Sanz et al., 2001). Especially, around
holes or fractures, the bone tissue is very often thinned out and the edges
are rounded (Bochenski et al., 1993, 1998; Hockett, 1996). The articular
ends of bones are often corroded (Sanz et al., 2001). Digestive enzymes
and stomach acids can further cause polishing and staining of bones
(Hockett, 1996 and references herein) as well as exfoliation (Andrews,
1990). These stomach fluids and additional mucus ease regurgitation of
the indigestible material and bind together the more or less loose parts.
Even when regurgitated higher up in the water column this slime prob-
ably gives the regurgitation considerable cohesion and prevents the hard
parts from being scattered widely over the sea or lake floor. The lack of
any fecal matrix (Sanz et al., 2001) provides an additional criterion to
identify (fossil) regurgitalites. Observations of various pellet-casting birds
resulted in a large number of factors controlling the physical aspect of
regurgitations, especially the etching patterns on hard body parts (cf.
Hockett, 1996). As an example, such factors may be the time interval
between swallowing and regurgitation (Duke et al., 1976), the pH of the
stomach solution (Duke et al., 1975) or the power of digestive enzymes
(Hockett, 1996). These factors will most likely also be present in other
groups than birds and impact the aspect of the regurgitated material.
Fossil regurgitalites are especially known from calm-water envi-
ronments, where their preservation potential is high. Regurgitations thus
are known from the Lower Jurassic Posidonia Shales of Holzmaden (Fig.
2; Keller, 1977; Böttcher, 1989, 1990), the Upper Jurassic Lithographic
Limestones of Solnhofen (Janicke, 1970; Barthel and Janicke, 1970) and
Nusplingen in southern Germany (Fig. 1; Schweigert et al., 2001) or the
Early Cretaceous Las Hoyas lacustrine limestones in Spain (Sanz et al.,
2001), to cite a few examples.
Regurgitations of invertebrates are mainly referred to as
pseudofeces. Suspension-feeding molluscs gather food by filtering sus-
pended particles out of the water with their gills. Mucus binds these
particles and then they are transported to the palps beside the mouth
where they are sorted for edibleness. Those particles found inedible are
further bound in mucus and expelled from the system as pseudofeces.
Mucus-binding is essential for efficient ejection and allows these pellets
to survive as sand-sized sediment grains for some time. These regurgi-
tated mucus-bound pellets resemble feces quite closely, differing only in
not having passed through the bivalve's gut (e.g., Prins et al., 1991 and
references herein). In the fossil record, they therefore might be
misidentified as coprolites. Criteria to distinguish pseudofeces from real
fecal pellets seem not to have been studied, yet (Prins et al., 1991).
Gastroliths, stomach stones or gizzard stones also show signs of
etching by stomach acids. Remaining within the stomach or rumen (or
similar) longer than regurgitated material, they show additional abrasion
and may sometimes be highly polished (Wings, 2003). Wings (2004)
made experiments in artificial stomachs in order to find criteria for distin-
guishing gastroliths from isolated exotic pebbles. According to his experi-
ments, polishing of the stones within the gizzard does not take place and
therefore has to occur after the death of the gastrolith-bearing animal.
Additionally, Schmeisser and Flood (2008) showed that geogastroliths
very often show subparallel grooves on the etched surfaces.
Gastroliths can perform several tasks. They occur regularly in
several groups of vertebrates (e.g., archosaurs, pinnipeds) but also in
invertebrates (e.g., crustaceans). A classification system and a redefini-
tion for gastroliths was provided by Wings (2004, 2007). According to
Wings (2004, 2007), gastroliths are hard objects of non-caloric value
(stones, natural and pathological concretions) which are or were retained
in the digestive tract of animals, and have a minimum diameter of
0.063 mm. Their external features, especially roundness and surface
texture, strongly depend on the function of the stones. Additionally,
other factors such as rock type, retention time or abrasion rate in the
stomach influence the physical appearance of gastroliths.
Wings (2004, 2007) distinguishes between three different types
of gastroliths: bio-gastroliths, patho-gastroliths and geo-gastroliths. This
subdivision is based on the type of origin: Biogastroliths are non-patho-
logical invertebrate concretions such as stomach concretions formed in
arthropods. Especially some crustacean species reabsorb calcium from
their old cuticle and store it in the form of gastrolithic concretions for
later reuse after their ecdysis (Scheer, 1964). After moulting, these con-
cretions are “digested” and the calcium is absorbed from the digestive
tract, transported by blood and finally re-utilized for calcification of the
new exoskeleton (e.g., Frizzell and Exline, 1958; Ueno et al., 1992). Due
to their origin and the fact that no substrate material has been modified in
this group, biogastroliths are not included within the Digestichnia (cf.
Bertling et al., 2006).
Pathogastroliths are stone-like concretions that are mainly gener-
ated in the stomachs of herbivorous mammals by swallowed and felted
hair or plant fibers. Such “stones” are also called “bezoar stones,” due to
their abundance in stomachs of the bezoar goat (e.g., Elgood, 1935).
Following Bertling et al. (2006), the felted hair and plant fibers have to be
regarded as substrate modification. Pathogastroliths therefore are in-
cluded within the Digestichnia.
Finally, Wings (2004, 2007) defined his geogastrolith as swal-
FIGURE 1. Regurgitated Plegiocidaris crucifer (Agassiz), SMNS 65411.
The echinoid crushed by the teeth of the predator is clearly visible by its
incomplete spines (black arrows) and skeletal ossicles (white arrows). The
echinoid fragments were probably held together by mucus that eased the
regurgitation process for the predator and increased the preservation
potential as a regurgitalite. Nusplingen (SW-Germany), Upper Jurassic, Upper
Kimmeridgian, Scale bar is 1 cm.
133
lowed pebbles and sand (the term “grit” is used for smaller geogastrolith
grain sizes in the range of sand with a minimum diameter of 0.63mm in
birds). When these rock grains are deposited in a gizzard (muscular
stomach used for grinding food particles), “gizzard stones” can therefore
be used as a synonym. Another rather rarely used term for geogastroliths
is “belly boulders.”
For isolated exotic rocks discovered in fine-grained sediments,
Wings (2004, 2007) introduced the term “exoliths.” These may show a
high polish and potentially (but not necessarily) might have been former
gastroliths.
Geogastroliths, or more precisely, the modifications on their sur-
faces (like etchings and abrasion) have to be regarded as trace fossils
according to Bertling et al. (2006). For exoliths, their origin from an
animal's digestive organ needs to be proven beyond reasonable doubt.
Criteria for the recognition of gastroliths isolated from any animal re-
mains were published by Weems et al. (2007) and Schmeisser and Flood
(2008) and do not need to be repeated here. However, their studies were
restricted to gastroliths originating from larger vertebrates.
POSSIBLE ICHNOTAXOBASES FOR DIGESTICHNIA
In order to name trace fossils, ichnotaxobases need to be defined
(Bertling et al., 2006). According to Fürsich (1974) and Bertling et al.
(2006), highly significant behavior reflected in trace fossils should be
used to distinguish trace fossils at ichnogeneric level and less significant
behavior for ichnospecific determination. Bertling et al. (2006) compiled
and discussed several commonly used characteristics in distinguishing
trace fossils, from which not all are suitable for the Digestichnia. Up to
now, not many ichnotaxa have been erected for Digestichnia, when com-
pared to other trace fossils. The following list of ichnotaxobases is based
on extant ichnotaxa for Digestichnia and will probably be extended in the
future. It should only be used as a rough guideline and as a basis for
further discussion.
Gastroliths
From the three major groups of Digestichnia (coprolites/feces,
regurgitalites and gastroliths), the gastroliths provide the least character-
istics that could be used as ichnotaxobases. Gastroliths are also the group
of Digestichnia that is least understood and most rarely investigated in
detail (Wings, 2004, 2007; Weems et al., 2007; Schmeisser and Flood,
2008). So far, no ichnotaxon has been erected for gastroliths.
Although pathogastroliths might not be preserved in the fossil
record, they should be distinguished from geogastroliths at the
ichnogeneric, if not an even higher, level. The felting of plant fibers and/
or hairs inside the stomach into pebble-like pathogastroliths clearly dif-
fers from the behavior reflected by geogastroliths (see above). Principal
composition, arrangement of components as well as their size distribu-
tion may provide ichnotaxobases here.
According to Wings (2004, 2007), the grain size of the
geogastroliths is highly variable and is therefore not a suitable
ichnotaxobase. This is because the interaction of anatomical, ontogenetic
and geographic factors can hardly be resolved: The grainsizes contained
in the gizzard depend on the maximum size that can be swallowed and
comfortably passed through the esophagus of the tracemaker. Their mini-
mum size reflects the diameter of the distal exit of the gizzard (cf. Wings,
2004). Gastroliths recovered from the bowels therefore should be smaller
or have the same size as the smallest gastroliths within the gizzard. On
the other hand, gizzards of large tracemakers can contain geogastroliths
with larger diameters than the gizzards of smaller tracemakers. The range
between maximum and minimum grain size may therefore be wider in
larger tracemakers than it is in smaller ones. But, during ontogeny, this
size range of geogastroliths will increase according to the body size of the
tracemaker.
Finally, the type of substrate rocks theoretically may seem to be
a useful ichnotaxobase at the ichnospecies level. Wings (2004) showed
that some ostriches prefer rocks of certain sizes and colors. On the other
hand, he also states that the real “selection” occurs in the gizzard. Soft
rocks are quickly eroded and carbonates become dissolved, leaving mainly
the most durable rock types, such as quartz varieties and quartzitic rocks
(Wings, 2004; Wings and Sander, 2007). In addition, rock types available
in the living space of the tracemakers will limit their choices. Based on
these considerations, prevailing rock types will not be useful ichotaxobases
in praxis.
Possible ichnotaxobases for geogastroliths may be found on closer
inspection of the surface microstructures. The study of Schmeisser and
Flood (2008), however, suggests that they strongly depend on the com-
position, texture and structure of the host rock, pointing to the necessity
of future research into this issue.
Regurgitalites
No ichnotaxon has been established for regurgitalites to date. The
size and shape of any regurgitated mass depends on the food it was
derived from. Indigestible content may be held together by felted plant
fibers, hair or feathers and/or mucus to form a pellet (e.g., Fitch et al.,
1946) or may have a more amorphous outline. Depending on the sedi-
mentary environment and the amount of slime adhesive to the indigest-
ible food particles, these regurgitalites may lie together on a spot (mainly
bird pellets, but also in marine environments, cf. Schweigert et al., 2001)
or might be scattered over a certain area (e.g., Dietl and Schweigert,
2001). Modern pellets of diurnal birds of prey and owls differ from each
other in shape, as well as in type, size range and arrangement of their
components. In modern owls and birds of prey, prey is usually swal-
lowed in one piece, but some (e.g. Glaucidium passerinum and Buteo
jamaicensis) break bones of prey animals with their beaks (Fitch et al.,
1946; Mebs and Scherzinger, 2000) and eat their prey in small pieces.
Depending on the time between ingestion and regurgitation and the
strength of the digestive liquids, hard body parts show different stages of
corrosion. The intactness of hard parts of the prey combined with the
FIGURE 2. A small ichthyosaur (cf. Stenopterygius quadrissicus) as a possible
regurgitalite of a larger ichthyosaur (discussion in Keller 1977), SMNS
15194. The isolated ribs and vertebrae inside (arrow) the curled ichthyosaur
belonging to this skeleton, the lack of the smallest caudal vertebrae as well
as the extreme torsion of the body all mark it as a regurgitalite. Due to the
rather rough preparation (chipping) of this specimen, surface pitting (cf.
Hockett, 1996; cf. Sanz et al., 2001) might not be preserved. Holzmaden
(SW-Germany), Lower Jurassic, Toarcian, Scale bar is 10 cm.
134
overall shape and size of the regurgitation could therefore be used at the
ichnogeneric level. The content might vary due to different diets during
the seasons, however (e.g., more insect-rich in summer), and might be
better used at ichnospecific level.
Invertebrate regurgitations are hardly known as yet. The diffi-
culty to distinguish between pseudofeces and real feces further compli-
cates the matter. Suggestions for possible ichnotaxobases of invertebrate
regurgitalites can therefore not be given to date.
Coprolites
The distinctive and reoccurring patterns of coprolites of inverte-
brate and vertebrate origin have been recognized early, thus a number of
(mainly monospecific) ichnogenera already exists (e.g., Häntzschel, 1975;
Hunt et al., 1998). Hunt and Lucas (2010) listed and discussed criteria
that can be used for assigning vertebrate coprolites to their tracemakers.
Most of these criteria are also helpful in describing feces and coprolites
and therefore could be used as ichnotaxobases. The ones suitable as
ichnotaxobases for both invertebrate and vertebrate feces/coprolites are
listed and discussed in the following.
Although absolute size is not recommended as an ichnotaxobase
by Bertling et al. (2006) for the majority of trace fossils, some vertebrate
and invertebrate feces (especially fecal pellets from e.g., rodents, and
bats or invertebrate microcoprolites, e.g., Favreinidae) exhibit a very
narrow size range (e.g., Häntzschel, 1975; Schweigert et al., 1997; Strachan,
2010). For the majority of feces (other than fecal pellets), however, size
is not a useful ichnotaxobase.
External shape has been used to distinguish coprolite ichnogenera
and ichnospecies. Just as for any other trace fossils, shape-defining
ratios of e.g., length to width or diameter are good ichnotaxobases for
coprolites of invertebrate and vertebrate tracemakers (e.g., Hunt et al.,
2005b, 2007). Not only the overall shape of coprolites but also their
surface texture (e.g., smooth, striations, incisions, etc.) or whether they
are built up out of concavo-convex subunits (cf. Milàn and Hedegaard,
2010) can be used to define ichnogenera or -species. An overview of the
most abundant coprolite shapes was given by Häntzschel et al. (1968).
Some of the external shapes illustrated by Häntzschel et al. (1968) might
also be useful in defining ichnotaxa for pellet-shaped regurgitations.
Especially in microcoprolites, the internal structure (e.g., number,
shape and arrangement of internal canals) is used to define both ichnogenus
and -species (Vialov, 1978; Schweigert et al., 1997 and further references
therein; Senowbari-Daryan and Kube, 2003 and further references therein).
Internal structures are also observed in vertebrate macrocoprolites (Hunt
et al., 2005a, cf. also Schweigert, this volume), which are used to define
ichnotaxa.
A carnivore, herbivore or omnivore diet is reflected in the content
of coprolites (Thulborn, 1991). Due to preservational bias (Hunt et al.,
1994), the fossil record of herbivore coprolites is much sparser than of
carnivore feces. Phosphatically preserved coprolites are usually assigned
to carnivore tracemakers (Hunt et al., 1994; Hunt and Lucas, 2010).
Different diets reflect an important animal behavior and therefore are
useful high-level ichnotaxobases in most cases. However, in omnivores,
the diet may change seasonally according to available food sources.
When hard body parts of the prey animals are not regurgitated but
passed through the digestive system, the strength of the predator's diges-
tive liquids will have different impact on the corrosion of ingested bones
and teeth. As an example, coprolites bearing teeth without enamel are
believed to derive from crocodilian tracemakers (e.g. Hunt and Lucas,
2010 and further references therein).
Summarizing, it is very difficult to define ichnotaxobases for
Digestichnia other than coprolites. Differing from all other ethological
classes, the overall appearance of Digestichnia is influenced by a variety
of parameters such as diet, strength of digestive liquids, etc. A combina-
tion of all available parameters should therefore be used to distinguish
ichnogenera. For the distinction at ichnospecies level, recurring varia-
tions in these parameters may be used.
CONCLUSIONS
The new ethological class Digestichnia (originally proposed by
Vialov, 1972) is introduced. The class Digestichnia is suggested to in-
clude all trace fossils (and Recent equivalents) produced by the digestive
process, which are two out of three types of gastroliths (geo- and
pathogastroliths sensu Wings, 2004, 2007), regurgitalites and coprolites/
feces. Any material of non-caloric value leaving the digestive tract of the
tracemaker in either way has to be regarded as a digestion trace (cf.
Bertling et al., 2006) and is therefore included within the new ethological
class Digestichnia. However, in the fossil record, individual bones or
other hard body parts preserved within Digestichnia may in addition still
be regarded as body fossils and treated as such. The trace fossil is made
up by the accumulation of undigested material deriving from the diges-
tive organs.
A combination of all available data is proposed as ichnotaxobases
at the ichnogeneric level. At the ichnospecific level, recurring variations
in these criteria should be used.
ACKNOWLEDGMENTS
Günter Schweigert and Ronald Böttcher (both Stuttgart, Germany)
kindly provided valuable information about regurgitalites from southern
Germany and provided admittance to the collections of the Staatliches
Museum für Naturkunde Stuttgart (SMNS). Markus Bertling (Münster,
Germany) kindly shared his research about the origin of the term
Faecichnia. Richard G. Bromley (Copenhagen, Denmark) corrected and
commented on an earlier draft of the above article. Markus Bertling
(Münster, Germany) and Adrian Hunt (Everett, USA) reviewed this
paper, thereby improving its quality.
REFERENCES
Abel, O., 1935, Vorzeitliche Lebensspuren: Jena, Fischer, 644 p.
Andrews, P., 1990, Owls, caves and fossils: Predation, preservation and
accumulation of small mammal bones in caves, with an analysis of the
Pleistocene cave faunas From Westbury-Sub-Mendip, Somerset, U.K.:
London, Natural History Museum Publications, 239 p.
Andrews, P. and Fernández-Jalvo, Y., 1998, 101 uses for fossilized faeces:
Nature, v. 393, p. 629-630.
Barthel, K.W. and Janicke, V., 1970, Aptychen als Verdauungsrückstand –
Ein Fund aus den Solnhofener Plattenkalken, unteres Untertithon,
Bayern: Neues Jahrbuch für Geologie und Paläontologie, Monatshefte,
v. 1970, p. 65-68.
Bertling, M., Braddy, S.J., Bromley, R.G., Demathieu, G.R., Genise, J.,
Mikuláš, R., Nielsen, J.K., Nielsen, K.S.S., Rindsberg, A.K., Schlirf, M.
and Uchman, A., 2006, Names for trace fossils: a uniform approach:
Lethaia, v. 39, p. 265–286.
Bochenski, Z.M., Tomek, T., Boev, Z. and Mitev, I., 1993, Patterns of
birdbone fragmentation in pellets of the tawny owl (Strix aluco) and the
eagle owl (Bubo bubo) and their taphonomic implications: Acta
Zoologica Cracoviensia, v. 36, p. 313–328.
Bochenski, Z.M., Huhtala, K., Jussila, P., Pulliainen, E., Tornberg, R. and
Tunkkari, P.S., 1998, Damage to bird bones in pellets of Gyrfalcon
Falco rusticolus: Journal of Archaeological Science, v. 25, p. 425–433.
Böttcher, R., 1989, Über die Nahrung eines Leptopterygius (Ichthyosauria,
Reptilia) aus dem süddeutschen Posidonienschiefer (Unterer Jura) mit
Bemerkungen über den Magen der Ichthyosaurier: Stuttgarter Beiträge
zur Naturkunde, Serie B, v. 155, p. 1–19.
135
Böttcher, R., 1990, Neue Erkenntnisse über die Fortpflanzungsbiologie der
Ichthyosaurier (Reptilia): Stuttgarter Beiträge zur Naturkunde, Serie B,
v. 164, p. 1–51.
Bromley, R.G., 1996, Trace fossils: Biology, taphonomy and applications:
London, Chapman and Hall, 361 p.
Dietl, G. and Schweigert, G., 2001, Im Reich der Meerengel – Fossilien aus
dem Nusplinger Plattenkalk: Munich, Pfeil, 144 p.
Duke, G.E., Jegers, A.A., Loff, G. and Evanson, O.A., 1975, Gastric diges-
tion in some raptors: Comparative Biochemistry and Physiology, v.
50A, p. 649–656.
Duke, G.E., Evanson, O.A. and Jegers, A., 1976, Meal to pellet intervals in
14 species of captive raptors: Comparative Biochemistry and Physiol-
ogy, v. 53A, p. 1–6.
Elgood, C., 1935, A treatise on the bezoar stone: Annals of Medical History,
v. 7, p. 73–80.
Fisher, D.C., 1981, Crocodilian scatology, microvertebrate concentrations,
and enamel-less teeth: Paleobiology, v. 7, p. 262–275.
Fitch, H.S., Swenson, F. and Tillotson, D.F., 1946, Behavior and food habits
of the red-tailed hawk: The Condor, v. 48, p. 205–237.
Frizzell, D.L. and Exline, H., 1958, Crustacean gastroliths from the Claiborne
Eocene of Texas: Micropaleontology, v. 4: p. 273–280.
Fürsich, F.T., 1974, On Diplocraterion Torell 1870 and the significance of
morphological features in vertical, spreiten-bearing, U-shaped trace fos-
sils: Journal of Paleontology, v. 48, p. 952–962.
Gibert, J.M. de, Domènech, R. and Martinell, J., 2004, An ethological
framework for animal bioerosion trace fossils upon mineral substrates
with proposal of a new class, fixichnia: Lethaia, v. 37, p. 429–437.
Häntzschel, W., 1975, Trace fossils and Problematica; in Moore, R.C. and
Teichert, C. eds., Treatise on Invertebrate Paleontology, v. W: Boulder,
Lawrence, Geological Society of America, University of Kansas, 269 p.
Häntzschel, W., El-Baz, F. and Amstutz, G.C., 1968, Coprolites – An anno-
tated bibliography: Geological Society of America, Memoir 108, 132 p.
Hockett, B.S., 1996, Corroded, thinned and polished bones created by golden
eagles (Aquila chrysaetos): Taphonomic implications for archaeologi-
cal interpretations: Journal of Archaeological Science, v. 23, p. 587–
591.
Hunt, A.P., 1992, Late Pennsylvanian coprolites from the Kinney Brick
Quarry, central New Mexico, with notes on the classification and utility
of coprolites: New Mexico Bureau of Mines and Mineral Resources,
Bulletin 138, p. 221–229.
Hunt, A.P. and Lucas, S.G., 2010, Crocodylian coprolites and the identifica-
tion of the producers of coprolites: New Mexico Museum of Natural
History and Science, Bulletin 51, p. 219–226.
Hunt, A.P., Chin, K. and Lockeley, M.G., 1994, The palaeobiology of
coprolites; in Donovan, S.K., ed., The palaeobiology of trace fossils:
London, Wiley, p. 221–240.
Hunt, A.P., Lucas, S.G. and Spielmann, J.A., 2005a, Biochronology of Early
Permian vertebrate coprolites of the American Southwest: New Mexico
Museum of Natural History and Science, Bulletin 31, p. 43-45.
Hunt, A.P., Lucas, S.G. and Spielmann, J.A., 2005b, Early Permian verte-
brate coprolites from north-central New Mexico with description of a
new ichnogenus: New Mexico Museum of Natural History and Science,
Bulletin 31, p. 39-42.
Hunt, A.P., Lucas, S.G., Spielmann, J.A. and Lerner, A.J, 2007, A review of
vertebrate coprolites of the Triassic with descriptions of new Mesozoic
ichnotaxa: New Mexico Museum of Natural History and Science, Bulle-
tin 41, p. 88-107.
Keller, T., 1977, Fraßreste im süddeutschen Posidonienschiefer: Jahreshefte
der Gesellschaft für Naturkunde in Württemberg, v. 132, p. 117–134.
Mebs, T. and Scherzinger, W., 2000, Die Eulen Europas – Biologie,
Kennzeichen, Bestände: Stuttgart, Franckh-Kosmos, 396 p.
Milàn, J. and Hedegaard, R., 2010, Interspecific variations in tracks and
trackways from extant crocodylians: New Mexico Museum of Natural
History and Science, Bulletin 51, p. 15–29.
Müller, A.H., 1962, Zur Ichnologie, taxiologie und Ökologie fossiler Tiere.
Teil 1: Freiberger Forschungshefte, v. C151, p. 5–30.
Patel, S.J. and Desai, B.G., 2009, Animal-sediment relationship of the Crus-
taceans and Polychaetes in the intertidal zone around Mandvi, Gulf of
Kachchh, Western India: Journal of the Geological Society of India, v.
74, p. 233–259.
Petzold, H.-G., 1959, Gewöllbildung bei Krokodilen: Zoologischer Anzeiger,
v. 163, p. 76–82.
Petzold, H.-G., 1967, Notizen zur Gewöllbildung bei einem Bindenwaran
(Varanus salvator) und einige allgemeine Bemerkungen über
Reptiliengewölle: Zoologischer Garten, v. 34, p. 134–138.
Prins, T.C., Smaal, A.C. and Pouwer, A.J., 1991, Selective ingestion of
phytoplankton by the bivalves Mytilus edulis L. and Cerastoderma
edule (L.): Hydrobiological, Bulletin 25, p. 93–100.
Sanz, J.L., Chiappe, L.M., Fernandez-Jalvo, Y., Ortega, F., Sanchez-Chillon,
B., Poyato-Ariza, F.J. and Pérez-Moreno, B.P., 2001, An Early Creta-
ceous pellet: Nature, v. 409, p. 998–1000.
Schäfer, W., 1962, Aktuo-Paläontologie nach Studien in der Nordsee: Frank-
furt am Main, Kramer: 666 p.
Scheer, B.T., 1964, Animal physiology: New York, Wiley, 409 p.
Schmeisser, R.L. and Flood, T.P., 2008, Recognition of paleogastroliths
from the Lower Cretaceous Cedar Mountain Formation, Utah using a
Scanning Electron Microscope: Ichnos, v. 15, p. 72–77.
Schweigert, G., Seegis, D.B., Fels, A. and Leinfelder, R.R., 1997, New inter-
nally structured decapod microcoprolites from Germany (Late Triassic/
Early Miocene), southern Spain (Early/Middle Jurassic) and Portugal
(Late Jurassic): Taxonomy, palaeoecology and evolutionary implica-
tions: Paläontologische Zeitschrift, v. 71, p. 51–69.
Schweigert, G., Dietl, G. and Wild, R., 2001, Miscellanea aus dem Nusplinger
Plattenkalk (Ober-Kimmeridgium, Schwäbische Alb). 3. Ein Speiballen
mit Flugsaurierresten: Jahresberichte und Mitteilungen des oberrheinischen
geologischen Vereins, v. 83, p. 357–364.
Seilacher, A., 1953, Studien zur Palichnologie, Teil I: Über die Methoden der
Palichnologie: Neues Jahrbuch für Geologie und Paläontologie,
Abhandlungen, v. 96, p. 421–452.
Seilacher, A., 2007, Trace fossil analysis: Berlin, Springer, 226 p.
Senowbari-Daryan, B. and Kube, B., 2003, The ichnogenus Palaxius (crus-
tacean coprolite) and description of P. hydranensis n. sp. from the
Upper Triassic (Norian part of “Pantokrator” limestone) of Hydra
(Greece): Paläontologische Zeitschrift, v. 77, p. 115–122.
Strachan, R., 2010, Mammal detective: Stansted, Whittet Books, 4. ed.,
128 p.
Thulborn, R.A., 1991, Morphology, preservation and paleobiological sig-
nificance of dinosaur coprolites: Palaeogeography, Palaeoclimatology,
Palaeoecology, v. 83, p. 341–366.
Ueno, M., Bidmon, H.J. and Stumpf, W.E., 1992, Ecdysteroid binding sites
in gastrolith forming tissue and stomach during the molting cycle of
crayfish Procambarus clarkii: Histochemistry, v. 98, p. 1–6.
Vialov, O.S., 1972, The classification of the fossil traces of life: Proceedings
of the 24th International Geological Congress, section 7 (palaeontology),
p. 639–644.
Vialov, O.S., 1978, Favreinidae (coprolites of Crustacea) from Turonian of
the Lower Amudaria: Paleontologicheskij Sbornik, v. 15, p. 58–67 [in
Russian].
Weems, R.E., Culp, M.J. and Wings, O., 2007, Evidence for prosauropod
dinosaur gastroliths in the Bull Run Formation (Upper Triassic, Norian)
of Virginia: Ichnos, v. 14, p. 271–295.
Wings, O., 2003, The function of gastroliths in dinosaurs – new consider-
ations following studies on extant birds: Journal of Vertebrate Paleontol-
ogy, v. 23 (suppl. to no. 3), p. 111A.
Wings, O., 2004, Identification, distribution, and function of gastroliths in
dinosaurs and extant birds with emphasis on ostriches (Struthio camelus)
[Ph.D. dissertation]: Bonn, University of Bonn, 187 p. Published online,
http://hss.ulb.uni-bonn.de:90/2004/0462/0462.htm
Wings, O., 2007, A review of gastrolith function with implications for fossil
vertebrates and a revised classification: Acta Palaeontologica Polonica,
v. 52, p. 1–16.
Wings, O. and Sander, P.M., 2007, No gastric mill in sauropod dinosaurs:
new evidence from analysis of gastrolith mass and function in ostriches:
Proceedings of the Royal Society, v. B274, p. 635–640.
