Abstract
Well-preserved mycelia of fungal- or saprolegnia-like biota mineralised by ferromanganese oxides were found for the first time in long bones of Late Cretaceous dinosaurs from the Gobi Desert (Nemegt Valley, Mongolia). The mycelia formed a biofilm on the wall of the bone marrow cavity and penetrated the osteon channels of the nearby bone tissue. Optical microscopy, Raman, SEM/EDS, SEM/BSE, electron microprobe and cathodoluminescence analyses revealed that the mineralisation of the mycelia proceeded in two stages. The first stage was early post-mortem mineralisation of the hyphae by Fe/Mn-oxide coatings and microconcretions. Probably this proceeded in a mildly acidic to circumneutral environment, predominantly due to heterotrophic bacteria degrading the mycelial necromass and liberating Fe and Mn sorbed by the mycelia during its lifetime. The second stage of mineralisation, which proceeded much later following the final burial of the bones in an alkaline environment, resulted from the massive precipitation of calcite and occasionally barite on the iron/manganese-oxide-coated mycelia. The mineral phases produced by fungal biofilms colonising the interiors of decaying dinosaur bones not only enhance the preservation (fossilisation) of fungal remains but can also be used as indicators of the geochemistry of the dinosaur burial sites.
Highlights
Microbial alteration is an important but still poorly understood pathway for bone degradation [1]
In contrast to the well-understood biomineralisation phenomena observed in recent fungi and fungi-bacteria associations, there are only a few studies concerned with fungal or generally microbial biomineralisation in fossil bones and its influence on bone fossilisation and preservation [5, 6, 7, 8]
The aim of this work is to present the first known case of mineralised fungal or saprolegnialike mycelia preserved in dinosaur bones exemplified in samples from the Cretaceous Nemegt Formation (Gobi Desert, Mongolia)
Summary
Microbial alteration is an important but still poorly understood pathway for bone degradation [1]. Fungi and fungi-like saprolegnia (water moulds) are ubiquitous saprophytes widely recognised in the archeological record as bone-degrading organisms which dissolve the bone matrix, producing characteristic branching tunnels [2]. Fungi form mats and, in combination with bacteria, can form biofilms enabling the precipitation of minerals in environments often considered unfavourable for mineralisation [3, 4]. In contrast to the well-understood biomineralisation phenomena observed in recent fungi and fungi-bacteria associations, there are only a few studies concerned with fungal or generally microbial biomineralisation in fossil bones and its influence on bone fossilisation and preservation [5, 6, 7, 8].
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