Abstract A wide spectrum of tomographic techniques now exists for studying palaeontological specimens, but the suitability of these methods for assessing Earth’s oldest prokaryotic life has not been comprehensively investigated. We evaluated the ability of X-ray computed tomography – specifically X-ray microtomography – to reveal the morphology and petrological context of Precambrian microfossils, pseudofossils and biosedimentary structures, all of which are important in the origin and early evolution of life of Earth. The materials tested came from the Pilbara Craton of Western Australia (the 3.49 Ga Dresser Formation, the 3.46 Ga Apex chert and the 3.43 Ga Strelley Pool Formation) and the 1.88 Ga Gunflint Formation of Ontario, Canada. These units chart key developments in palaeobiology. The oldest formations contain profoundly controversial microfossil-like objects and microbially-induced sedimentary structures, whereas definitive prokaryotes are found in the youngest formations. We demonstrate that the imaging of individual microfossils and pseudofossils currently lies at the limits of the capabilities of laboratory-based X-ray microtomography and requires beneficial taphonomy. However, microtomography does provide a good overview of their petrological context at flexible spatial scales, although the quality of the data obtained from mesoscopic microbially-induced sedimentary structures and stromatolites depends largely on their style of preservation. Supplementary material: A zipped Drishti volume for all CT scans, a 0.7z split zip file of one Drishti volume and a HDMI supplementary movie showing digital visualizations for all of the scans are available at https://doi.org/10.5281/zenodo.58161

Abstract This paper outlines the suite of advanced multi-scalar techniques currently available in the toolkit of the modern Proterozoic palaeobiologist. These include non-intrusive and non-destructive optical, laser and X-ray techniques, plus more destructive ion beam and electron beam methods. Together, these provide morphological, mineralogical and biochemical data at flexible spatial scales from that of an individual atom to the largest Proterozoic microfossils. An overview is given of each technique and a case study from the exceptionally well-preserved Torridonian biota of NW Scotland is presented. This microfossil assemblage was first recognized over a century ago, but its great diversity and evolutionary importance has only recently come to light, due in no small part to the research efforts of Martin Brasier.

Abstract It has become accepted in recent years that the fossil record can preserve labile tissues. We report here the highly detailed mineralization of soft tissues associated with a naturally occurring brain endocast of an iguanodontian dinosaur found in c. 133 Ma fluvial sediments of the Wealden at Bexhill, Sussex, UK. Moulding of the braincase wall and the mineral replacement of the adjacent brain tissues by phosphates and carbonates allowed the direct examination of petrified brain tissues. Scanning electron microscopy (SEM) imaging and computed tomography (CT) scanning revealed preservation of the tough membranes (meninges) that enveloped and supported the brain proper. Collagen strands of the meningeal layers were preserved in collophane. The blood vessels, also preserved in collophane, were either lined by, or infilled with, microcrystalline siderite. The meninges were preserved in the hindbrain region and exhibit structural similarities with those of living archosaurs. Greater definition of the forebrain (cerebrum) than the hindbrain (cerebellar and medullary regions) is consistent with the anatomical and implied behavioural complexity previously described in iguanodontian-grade ornithopods. However, we caution that the observed proximity of probable cortical layers to the braincase walls probably resulted from the settling of brain tissues against the roof of the braincase after inversion of the skull during decay and burial. Supplementary material: Information regarding associated fossil material, and additional images, can be found at https://doi.org/10.6084/m9.figshare.c.3519984 Gold Open Access: This article is published under the terms of the CC-BY 3.0 license .