Fossil Record 20(2): 173-199, doi: 10.5194/fr-20-173-2017
Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT
expand article infoMax Wisshak, Jürgen Titschack§, Wolf-Achim Kahl|, Peter Girod
‡ Senckenberg am Meer, Marine Research Department, 26382 Wilhelmshaven, Germany§ MARUM – Center for Marine Environmental Sciences, 28359 Bremen, Germany| Bremen University, Geosciences, 28359 Bremen, Germany¶ Holteistraße 2, 10245 Berlin, Germany
Open Access
The ongoing technical revolution in non-destructive3-D visualisation via micro-computed tomography (micro-CT) finds a valuableapplication in the studies of bioerosion trace fossils, since theirthree-dimensional architecture is hidden within hard substrates. Thistechnique, in concert with advanced segmentation algorithms, allows adetailed visualisation and targeted morphometric analyses even of thosebioerosion traces that are otherwise inaccessible to the widely appliedcast-embedding technique, because they either are filled with lithifiedsediment or cementor are preserved in inherently insoluble or silicifiedhost substrates, or because they are established type material and shouldnot be altered.

In the present contribution selected examples of such cases are illustratedby reference to bioerosion trace fossils preserved in Late Cretaceousbelemnite guards from the European Chalk Province. These case studiescomprise an analysis of a diverse ichno-assemblage found associated with thelectotype of the microboring Dendrina dendrina (Morris, 1851) in a belemnite from the upperCampanian to lower Maastrichtian chalk of Norfolk, England, and thedescription of two new bioerosion trace fossils with type specimens found inbelemnite guards from the lower Campanian limestones of Höver, Germany.The latter are Lapispecus hastatus isp. n., a tubular and occasionally branched macroboring forwhich a sipunculan or a phoronid trace maker are discussed, and Entobia colaria isp. n., acamerate network formed by an excavating sponge that eroded diagnosticgrated apertures at the locations of the presumed inhalant papillae orexhaling pores, adding to or replacing filtering devices that are otherwisemade of tissue and spicules.

As an added value to the non-destructive visualisation procedure, theprocessed X-ray micro-CT scans of the studied type material provide3-D models that may now serve as digitypes that can be studied as digitalfacsimile without the necessity of consulting the actual type specimens.