Although the fibrous plant material called Affenhaar from the middle Eocene lignites of Geiseltal in Germany has been repeatedly studied for over 172 years, modern imaging and chemical analyses have enabled a deeper understanding of its chemical composition and preservation within the parent plant. Known in English as “monkeyhair,” the fibrous material represents a very rare case of fossil laticifers, the latex-bearing ducts of plants. Here we use high-resolution X-ray microcomputed tomography (micro-CT) for the first time to elucidate the anatomy of tissues and their differential degradation within the monkeyhair tree. Even in large, fairly intact stem axes, the center cylinder of secondary xylem inside the trunks or branches is completely absent, presumably due to diagenetic degradation. Nevertheless, there is a moderately well-preserved outer layer of bark and mats of excellently preserved laticifers in the extraxylary zone beneath the bark. Previous chemical analyses revealed that the latex in these laticifers was dominated by natural rubber (cis-1,4-polyisoprene), but also included various triterpenoids. These fossil laticifers also contained large amounts of organic sulfur, suggesting the rubber may have been naturally vulcanized. Pyrolysis GC/MS is also applied to the fossil laticifers for the first time to identify the organic sulfur constituents of this ancient latex. The chemical analysis yields 12 major sulfur compounds, mostly thiophenes, consistent with vulcanized rubber. The vulcanization of these laticifers most likely occurred during early diagenesis, before the degradation of the wood, at low temperatures, and may have been facilitated with other compounds that served as accelerators, activators, and fillers.

Annulated discoidal structures are common in many Neoproterozoic and particularly Ediacaran successions. Their interpretations, especially their biogenicity, are often contentious. Some of them (e.g., Aspidella and related forms) are demonstrably biological structures and may represent holdfasts of frondose Ediacara-type organisms. Others may represent fluid escape structures or tool marks produced by the rotation of tethered organisms. Here we show that differential chemical weathering of diagenetic dolomite concretions can also produce annulated discoidal structures that could be mistaken as Ediacara-type discoidal fossils. Using transmitted-light and cathodoluminescence microscopy in conjunction with Raman and energy dispersive spectroscopy, we analyzed dolomitized discoidal concretions embedded in a phosphorite matrix from the Ediacaran Miaohe Member of South China. Our observations reveal that pervasive and displacive syn-compactional dolomitization of the concretions and differential compaction of surrounding sediment led to the formation of biconvex or upward-convex primary laminae within the concretions. When exposed along parting surfaces and/or bedding planes, disparities in the weatherability of the warped primary laminae within the concretions resulted in the formation of circular annuli that mimic Neoproterozoic discoidal structures, some of which have been contentiously interpreted as discoidal fossils. These findings emphasize the importance of thin-section petrographic observations in the study of discoidal dubiofossils in order to assess their origin as diagenetic concretions or as discoidal macrofossils.

Trace fossils such as bite marks provide rare, direct evidence of animal behavior, including predator-prey interactions. We present an osteoderm of the aetosaur Typothorax coccinarum from the Late Triassic Chinle Formation of Arizona with several punctures and scores, interpreted here as bite marks, preserved as evidence of predation/scavenging by a large carnivore. The marks include a single bite producing four subparallel fusiform pits on the ventral surface and several additional marks, including striated scores, on the dorsal surface. These traces are described and compared with known contemporaneous carnivorous taxa to determine the source of the bite marks. Some Triassic carnivores, including theropod dinosaurs can be ruled out because of tooth shape and serration densities. Phytosaurs and large paracrocodylomorphs remain as likely candidates based on tooth morphology. Although some phytosaur teeth are too rounded to produce the marks seen in this specimen, we demonstrate that the more lingually flattened teeth typically found in the posterior section of the snout are sufficiently mediolaterally compressed to produce a fusiform pit. A protective function for aetosaur osteoderms cannot be confirmed presently, but the extensive carapace these bones formed would have been a major barrier to both scavengers and active predators and may preserve more feeding/predation traces than previously thought. The bite marks described herein support the hypothesis that aetosaurs were prey items of large archosauromorphs, expanding our understanding of the complex, and seemingly carnivore dominated Late Triassic terrestrial ecosystems of North America.