René Hoffmann
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View article: Microstructural and geochemical evidence offers a solution to the cephalopod cameral deposits riddle
Microstructural and geochemical evidence offers a solution to the cephalopod cameral deposits riddle Open
Orthoceratoid cephalopods are common in the Palaeozoic rock record but went extinct in the Late Triassic. Many orthoceratoids contain cameral deposits, which are enigmatic calcareous structures within their chambered shell that presumably …
View article: Phylogeochemistry: exploring evolutionary constraints on belemnite rostrum element composition
Phylogeochemistry: exploring evolutionary constraints on belemnite rostrum element composition Open
The biogenic carbonate hard parts of a large range of marine organisms are among the most important geochemical archives of Earth's climate dynamics through time and the evolution of life. That said, biomineralization pathways, i.e. the se…
View article: Microstructural and geochemical evidence offers a solution to the cephalopod cameral deposits riddle
Microstructural and geochemical evidence offers a solution to the cephalopod cameral deposits riddle Open
Orthoceratoid cephalopods are common in the Palaeozoic rock record but became extinct in the Late Triassic. Many orthoceratoids contain cameral deposits, which are enigmatic calcareous structures within their chambered shell that presumabl…
View article: Palaeoenvironmental implications and genesis of lacustrine Lower Triassic giant ooids
Palaeoenvironmental implications and genesis of lacustrine Lower Triassic giant ooids Open
The sedimentary environment and mechanisms of formation of giant ooids (> 2 mm) are not well understood. Here, we use petrographical, mineralogical and geochemical data of giant ooids from the Lower Triassic Buntsandstein Formation of cent…
View article: Phylogeochemistry: exploring evolutionary constraints on belemnite rostrum element composition
Phylogeochemistry: exploring evolutionary constraints on belemnite rostrum element composition Open
The biogenic carbonate hardparts of a large range of marine organisms are the most important geochemical archives of Earth’s climate dynamics through time and the evolution of life. That said, biomineralisation pathways, i.e., the secretio…
View article: Towards an improved understanding of Ca–Mg carbonates with nonplanar surfaces: An experimental approach
Towards an improved understanding of Ca–Mg carbonates with nonplanar surfaces: An experimental approach Open
Saddle dolomite is a Ca–Mg carbonate characterized by curved crystal faces, curved cleavage and sweeping extinction under cross‐polarized light. Saddle dolomite and, generally, Ca–Mg carbonates with curved crystal faces, are often assigned…
View article: Microborings reveal alternating agitation, resting and sleeping stages of modern marine ooids
Microborings reveal alternating agitation, resting and sleeping stages of modern marine ooids Open
Ooids are abundant carbonate grains throughout much of Earth's history, but their formation is not well understood. Here, an in‐depth study of microbial bioerosion features of Holocene ooids from the Schooner Cays ooid shoals (Great Bahama…
View article: Unravelling calcite-to-aragonite evolution from a subsurface fluid - Formation pathway, interfacial reactions and nucleation effects
Unravelling calcite-to-aragonite evolution from a subsurface fluid - Formation pathway, interfacial reactions and nucleation effects Open
Calcite-aragonite alternations are documented in sedimentary deposits worldwide, but their formation is still poorly understood and individual CaCO3 precipitation pathways are rarely confirmed experimentally. Therefore, (sub)recent CaCO3 s…
View article: Mg/Ca carbonates with curved crystal surfaces: an experimental study
Mg/Ca carbonates with curved crystal surfaces: an experimental study Open
Dolomite, CaMg(CO3)2 and related Mg/Ca carbonates (disordered calcian dolomite, high Mg calcite, and similar) are common rock-forming minerals that occur widely in numerous diagenetic settings. They represent pore-filling precipitates (cem…
View article: Experimental precipitation of cryogenic calcite and vaterite
Experimental precipitation of cryogenic calcite and vaterite Open
Cryogenic cave carbonates (CCCs) are speleothems precipitated from freezing water bodies in caves. A series of scholarly papers have explored natural CCC precipitation kinetics, crystal habit, mineralogy, crystallography and geochemistry. …
View article: The intriguing shapes of the ammonoid whorl
The intriguing shapes of the ammonoid whorl Open
Morón-Alfonso, Daniel A., Cichowolski, Marcela, Hoffmann, René, Korn, Dieter, Vennari, Verónica V., Allaire, Ninon (2023): The intriguing shapes of the ammonoid whorl. Palaeontologia Electronica (a14) 26 (1): 1-23, DOI: 10.26879/1263, URL:…
View article: Bayesian inference reveals a complex evolutionary history of belemnites
Bayesian inference reveals a complex evolutionary history of belemnites Open
Belemnites are an extinct group of Mesozoic coleoid cephalopods, common in Jurassic and Cretaceous marine sedimentary rocks.Despite their significance, their total group phylogeny has rarely been considered in recent decades.In contrast, m…
View article: Bayesian inference reveals a complex evolutionary history of belemnites
Bayesian inference reveals a complex evolutionary history of belemnites Open
Belemnites are an extinct group of Mesozoic coleoid cephalopods, common in Jurassic and Cretaceous marine sedimentary rocks. Despite their significance, their total group phylogeny has rarely been considered in recent decades. In contrast,…
View article: Petrographic and geochemical constraints on the formation of gravity‐defying speleothems
Petrographic and geochemical constraints on the formation of gravity‐defying speleothems Open
Cave carbonates, seemingly growing in defiance of gravity, have attracted the community's interest for more than a century. This paper focusses on ‘helictites’, contorted vermiform speleothems with central capillaries. Petrographic, crysta…
View article: Ghost in the shell
Ghost in the shell Open
Invasive mammalian predators are arguably the most damaging group of alien animal species for global biodiversity. Thirty species of invasive predator are implicated in the extinction or endangerment of 738 vertebrate species—collectively …
View article: Complex Biomineralization Pathways of the Belemnite Rostrum Cause Biased Paleotemperature Estimates
Complex Biomineralization Pathways of the Belemnite Rostrum Cause Biased Paleotemperature Estimates Open
Paleotemperatures based on δ18O values derived from belemnites are usually “too cold” compared to other archives and paleoclimate models. This temperature bias represents a significant obstacle in paleoceanographic research. Here we show g…
View article: Evolutionary development of the cephalopod arm armature: a review
Evolutionary development of the cephalopod arm armature: a review Open
The cephalopod arm armature is certainly one of the most important morphological innovations responsible for the evolutionary success of the Cephalopoda. New palaeontological discoveries in the recent past afford to review and reassess ori…
View article: Evolutionary–phylogenetic pathway of the Cretaceous ammonite genus <i>Aegocrioceras</i> and its relationship to <i>Juddiceras</i> spp. and <i>Crioceratites</i> spp.
Evolutionary–phylogenetic pathway of the Cretaceous ammonite genus <i>Aegocrioceras</i> and its relationship to <i>Juddiceras</i> spp. and <i>Crioceratites</i> spp. Open
The systematics of ammonoids are complicated by their large degree of intraspecies variation, which complicates a stable validation of species. Aegocrioceras is a heteromorph ammonite from the Lower Saxony Basin in the Hauterivian Boreal, …
View article: Botryoidal and Spherulitic Aragonite in Carbonates Associated with Microbial Mats: Precipitation or Diagenetic Replacement Product?
Botryoidal and Spherulitic Aragonite in Carbonates Associated with Microbial Mats: Precipitation or Diagenetic Replacement Product? Open
Similar carbonate fabrics may result from different pathways of precipitation and diagenetic replacement. Distinguishing the underlying mechanisms leading to a given carbonate fabric is relevant, both in terms of an environmental and diage…
View article: Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites
Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites Open
Because of physiology of coleoids, their fossils preserve soft-tissue-remains more often than other cephalopods. Sometimes, the phosphatized soft-tissues, particularly parts of the muscular mantle, display dark circular patterns. Here, we …