Extended Data Fig. 1: Spectral plots that validate the Raman bands indicative of biliverdin and protoporphyrin IX relative to PFPs, based on three representative samples.

Spectral plots are 200–1,600 cm⁻¹ ± 2 cm⁻¹, from 6 accumulations; spectra are baselined and normalized. Each spectrum was repeated three times independently, and yielded similar results. The lowermost spectral plot depicts blue spectra for biliverdin (from D. novaehollandiae eggshell), red spectra for protoporphyrin IX (from G. domesticus) and brown spectra for fossil proteinaceous soft tissue (from A. fragilis bone; see previous study²⁶). The uppermost dark-brown spectra represent an in situ measurement for the H. huangi (NMNS CYN-2004-DINO-05) eggshell that is known to preserve both pigments (biliverdin and protoporphyrin IX). Blue asterisks label bands of biliverdin that differ from PFP; red asterisks label bands of protoporphyrin IX that are absent in fossil soft-tissue remains. Overall, 22 Raman bands are identified that can be generated only by original unaltered pigments, and not by PFPs that are simultaneously present.