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Microstructural characteristics and seasonal growth patterns observed in Metoposaurus krasiejowensis teeth

Weryński Łukasz, Kędzierski Mariusz

Geological Quarterly

2022

Vol. 66, No. 3

art. no. 26

The tooth microstructure of Metoposaurus krasiejowensis was studied to observe external morphology, internal microstructure (comprising dentine structure and directional porosity as possible predatory adaptations) and enamel/enameloid mineral composition. Scanning electron microscopy (SEM) observation and thin-section inspection by light microscope enabled us to recognize a directional porosity in the tooth cross-sections, interpreted here as a part of the labyrinthodont structure displayed by temnospondyls and related groups. This network of canals is highly complicated and reveals a three-dimensional structure. The teeth present different cross-sections based on the distance from the tip, with a wide, circular, reinforced base and lateral compressed, directional cuspidal section with cutting edge. Interestingly, the internal structure observed in M. krasiejowensis teeth exhibit a peculiar variation of internal structure of temnospondyl teeth, as the convoluted canal-like structure seems to be irregular and appears in the upper section of teeth, while teeth bases show a regular structure with a pulpal cavity circled by pores. Furthermore, bands of incremental growth marks interpreted as Andresen lines, characterized by pronounced colour variation, were observed with strong implications for seasonal growth patterns in dentine. Additionally, a significant proportion (1.43–2.73%) of fluoride was observed as a component of enamel by scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) point and mapping analyses, suggesting a fluorapatite mineralogy of enamel.

Maastrichtian climate changes : the calcareous nannofossil record from flysch deposits of the Outer Carpathians

Wierzbicki Adam, Kędzierski Mariusz

Annales Societatis Geologorum Poloniae

2020

Vol. 90, No. 4

447--462

The Outer Carpathians are known for a few sections, where transitions from the Upper Cretaceous to the Palaeogene, including the K-Pg boundary interval, were described. One of them, the Bąkowiec section in the Skole Nappe, was examined with reference to the record of biostratigraphy and palaeoenvironmental changes, mainly based on the analysis of calcareous nannofossil assemblages. This study shows no evidence for the K-Pg boundary; however, the presence of the nannofossil species Micula prinsii, marking the topmost Maastrichtian UC20dTP Zone, was noted. The appearance of this low-latitude taxon and relevant changes in the composition of nannofossil assemblages indicate an influx of Tethyan warm water into the northern Carpathian basins during the latest Maastrichtian, shortly before the K-Pg boundary event. Therefore, the authors infer that the upper part of the Bąkowiec section recorded the latest Maastrichtian warming of climate, probably triggered by Deccan volcanic activity.