Protein and chitin preservation in polymeric sheets from Ecphora gardnerae from Maryland, USA

In 2015, polymeric sheets were found within the shells of Ecphora gardnerae from the Miocene St. Mary’s Formation of Maryland, USA. These membranes were found to have amino acids and complex sugar compounds. To explore these further, four new E. gardnerae shells were collected and analyzed for proteins and sugar compounds. Using direct analysis in real time (DART) mass spectrometry, we were able to show that the membranes contain chitin. With mass spectrometry-based paleoproteomic techniques utilizing a hydroxylamine extraction or sample preparation by easy extraction and digestion (SPEED), we found preserved peptides from all four shells including peptides that are specific to Gastropoda or Mollusca. The proteins were generally cellular in origin suggesting that the membranes are composed of cells on or in a chitin network.