Based on data derived from computed tomography, we demonstrate that integrating 2D and 3D morphological data from ammonoid shells represents an important new approach for investigating the palaeobiology of ammonoids. Characterization of ammonite morphology has long been constrained to 2D data, with only a few studies collecting ontogenetic data in 180°steps. Here we combine this traditional approach with 3D data collected from high-resolution nano-computed tomography. Ontogenetic morphological data on the hollow shell of a juvenile ammonite Kosmoceras (Jurassic, Callovian) was collected. 2D data was collected in 10°steps and show significant changes in shell morphology. Preserved hollow spines show multiple mineralized membranes never reported before, representing temporal changes in the ammonoid mantle tissue. 3D data show that chamber volumes do not always increase exponentially, as was generally assumed, but may represent a proxy for life events, such as stress phases. Furthermore, chamber volume cannot be simply derived from septal spacing in forms comparable to Kosmoceras. Vogel numbers represent a 3D parameter for chamber shape, and those for Kosmoceras are similar to other ammonoids (Arnsbergites, Amauroceras) and modern cephalopods (Nautilus, Spirula). Two methods to virtually document the suture line ontogeny, used to document phylogenetic relationships of larger taxonomic entities, were applied for the first time and present a promising alternative to hand drawings. The curvature of the chamber surfaces increases during ontogeny due to increasing strength of ornamentation and septal complexity. As this may allow for faster handling of cameral liquid, it could compensate for decreasing SA/V ratios through ontogeny.

Calcareous nannofossils—very small‐scaled marine microfossils—occur in many archaeological materials. Foremost, these include limestones used in masonry, material which has not experienced significant modification by humans. Poorly documented are nannofossils in mortars, because the burning process of quicklime requires the heating of the raw material to > 800°C. Here we focus on calcareous nannofossils in mortar and mortar‐based samples of four medieval buildings in northern Germany. The study documents the presence of nannofossils in historic mortars. It supplies evidence for the provenance of the mortars used, thereby introducing a new tool for mortar provenance studies.

No abstract

Calcareous nannofossils are < 30 µm sized calcitic fossil remains of single-celled marine photoautotrophic algae. Carbonate-rich sedimentary rocks, containing these fossils, are used as raw material for lime-based mortars. The carbonates (CaCO3) are heated up to approx. 900 °C. The burning process, which causes the thermal decomposition of CaCO3 into CaO (= quicklime) and CO2, destroys the calcitic fossils. Surprisingly, remains of these calcareous algae were recently encountered in historic mortars and mortar-based materials. To gain a better understanding of the behaviour of calcareous nannofossils during the calcination procedure, four sample sets were heated to nine temperature levels (100 °C, 300 °C, 500 °C, 600 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C). For each sample set, the initial and the heated material of all nine temperature levels were analysed with respect to its nannofossil content and preservation by using settling slides. Our results show a decrease of absolute abundance and preservation from 500 °C onwards; rare nannofossils are preserved up to 900 °C. Changes in the relative abundance of individual species document that certain taxa are more heat resistant than others. This pattern is explained by different crystal sizes and forms of the relevant taxa. Differences in the calcareous nannofossil assemblages, observed in the raw material and in the mortar produced from it, can be used to estimate the temperature reached during quicklime production.