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Ecdysichnia : a new ethological category for trace fossils produced by moulting

Vallon L. H., Schweigert G., Bromley R. G., Röper M., Ebert M.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 3

433--444

EN

The shedding of exoskeletons is an important aspect of the lifecycle of some in vertebrates (mainly arthropods). To rid them selves of the old cuticula (= exuvia), these animals of ten have to thrash about, twist around or rub themselves against the sediment or other more or less solid objects. In softgrounds, this behaviour may create distinctive patterns that have to be regarded as trace fossils. Accordingly, some ichnospecies of Rusophycus have recently been interpreted as traces made during ecdysis. Most of the so-called “Schwoimarken” from the Solnhofen lithographic limestones (Upper Jurassic, SE Germany), usually interpreted as structures made by dead organisms swaying in response to water movements, must be understood as traces of arthropod ecdysis. In this context, we erect Harpichnus bartheli igen. et isp. nov. and propose the new ethological category, ecdysichnia, for moulting traces. In most “Schwoimarken” containing body-fossil remains other than arthropods, we see sediment displacement by scavenging arthropods rather than mortichnia (sensu Seilacher, 2007). We further propose inclusion of the recently erected category pupichnia for pupation chambers as a subcategory of ecdysichnia. In our opinion, pupation is a special form of moulting that does not justify the splitting of categories, as briefly noted by Vallon et al. (2013).

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Bioerosional ichnotaxa and the fossilization barrier

Bromley R. G., Nielsen K. S. S.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 3

453--455

EN

For the establishment of a new ichnogenus or ichnospecies, the type material shall be fossil, not unfossilized material. This is not always possible, because the transition between the two states, the fossilization barrier, is extremely vague defined. In most fossil material, this is not a problem. However, in the case of bioerosion structures (borings, rasping traces, attachment scars in hard substrates), the problem is serious. For example, when does a sponge boring in an oyster shell be come fossilized? The question arises when Recent and sub-Recent materials are considered. Two examples are discussed. (1) Microborings are described and named in foraminifera dredged from the sea floor. In this material, it is not possible to distinguish between “fossilized” and “unfossilized” foraminifera. Bioturbation and other processes may have mixed recently dead, Pleistocene and older foraminifera in the sea-floor sediments. (2) Small, characteristic borings are made by slipper limpets in pagurized gastropod shells. The structures would constitute a new ichnospecies of Oichnus, but these borings have not been found in “fossilized material” and the borings therefore remain nameless. Because bioerosion structures constitute “ready-made fossils”, it is suggested that the onset of fossilization be equated with the death of the bioeroding tracemaker.

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New ichnotaxa based on tooth impressions on dinosaur and whale bones

Jacobsen Aa. R., Bromley R. G.

Geological Quarterly

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2009

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Vol. 53, No 4

373-382

EN

Traces produced by teeth on bones provide a source of information on the feeding behaviour, predator-prey relationships, and tooth morphology of the tracemaking carnivores and scavengers involved. Studies on mammals, both fossil and recent, have used tooth-scratched bones as clues to the feeding behaviour of carnivorous, scaveng ing, mineral-seeking and tooth-sharpening mammals in various ecosystems. Similarly, theropod tooth traces have the potential of being important for studying the ecology and ethology of both carnivorous and herbivorous dinosaurs. This paper augments the ichnological nomenclature for traces made by teeth on bones. Two new ichnogenera and ichnospecies, Linichnus serratus and Knethichnus parallelum, are introduced on the basis of the morphology of theropod biting damage, to focus on the resulting trace fossils as an ichnological feature and to encourage further observation and studies of distrtibution. Using similar ichnological terminology for both theropod and mammalian feeding traces, and even those of selachian sharks preying on whales or scavenging their corpses, will help coordinate biting strategies, jaw mechanism and feeding behaviour for both recent and ancient carnivores and scavengers.