Raman spectroscopy is a powerful tool in molecular paleobiology: An analytical response to Alleon et al. (https://doi.org/10.1002/bies.202000295)

Abstract

A recent article argued that signals from conventional Raman spectroscopy of organic materials are overwhelmed by edge filter and fluorescence artefacts. The article targeted a subset of Raman spectroscopic investigations of fossil and modern organisms and has implications for the utility of conventional Raman spectroscopy in comparative tissue analytics. The inferences were based on circular reasoning centered around the unconventional analysis of spectra from just two samples, one modern, and one fossil. We validated the disputed signals with in situ Fourier‐Transform Infrared (FT‐IR) Spectroscopy and through replication with different lasers, filters, and operators in independent laboratories. Our Raman system employs a holographic notch filter which is not affected by edge filter or other artefacts. Multiple lines of evidence confirm that conventional Raman spectra of fossils contain biologically and geologically meaningful information. Statistical analyses of large Raman and FT‐IR spectral data sets reveal patterns in fossil composition and yield valuable insights into the history of life.

The diverse terminology of reptile eggshell microstructure and its effect on phylogenetic comparative analyses

“…pore structure and density, calcium concentration, crystalline structure of shell units, thickness and arrangement of protein fibers in the membrane) will be greatly improved by the systematic use of advanced microscopy and geochemistry techniques to visualize structures of interest with a much greater precision (e.g. X‐ray or Raman spectroscopy, EBSD, time‐of‐flight or inductively coupled mass spectrometry – Alleon et al, 2021; Campos‐Casal et al, 2020; Choi et al, 2019; Choi, Kim, et al, 2022; Loewy et al, 2020; Moreno‐Azanza et al, 2013; Wiemann et al, 2017; Wiemann & Briggs, 2022). Future use of such atomized single traits in a phylogenetic comparative context is thus expected to provide a much clearer picture of the evolution of eggshell microstructure in reptiles than that of a two‐ or three‐state character (D'Alba et al, 2021; Legendre & Clarke, 2021).…”

Non-avian dinosaur eggshell calcite can contain ancient, endogenous amino acids

“…2C). Some of the pattern in the M. megadermus A spectra is likely due to artefactual quasi-periodic ripples resulting from intense sample luminescence interacting with the edge filter on the Raman spectroscopy equipment we used (Alleon et al 2021;Wiemann & Briggs et al 2022), especially in the light regions of the eggshell. To help account for sample luminescence, future work could run pure calcite and organic standards for comparison or use wavelet transform analysis (Alleon et al 2021) or principal component analysis (Wiemann & Heck 2023).…”

Lower Crust Viscosity in Central Tibet Inferred From InSAR Derived Deformation Around Siling Co Lake After Its Rapid Expansion in the 2000s

“…To map the surface deformation resulted from the loading change of the Siling Co, we process Sentinel‐1 SAR images acquired from 2017 to 2022 (Table S1 in Supporting Information ). We conduct the SAR interferometry using the burst‐based processing chain implemented in the Sentinel‐1 Interferometry Processor (Jiang et al., 2017). We use the Shuttle Radar Topography Mission Digital Elevation Model for removing references phases and for co‐registration.…”

“…More details of SAR processing tools can be found from Jiang et al. (2017). The water level data and are surface data can be obtained from Schwatke et al.…”