Encrinus aculeatus (Crinoidea: Encrinida) with exceptional preservation of organic pigments from the Middle Triassic of Lower Silesia (SW Poland)

Abstract

The crinoid species Encrinus aculeatus v. Meyer, 1847 is reported for the first time from the Middle Triassic of Lower Silesia (North-Sudetic Synclinorium). The present paper describes two articulated crowns of this species, an adult and a juvenile(?) specimen, found in the Lower Muschelkalk of Raciborowice. Both specimens display a distinct purple to violet coloration. Chemical analysis based on ultraviolet/visible spectroscopy and mass spectrometry provides evidence that the characteristic color is due to the presence of organic compounds, fossil hypericinoid pigments, which are closely related to pigments of Recent crinoids. The new occurrence from the early Pelsonian Punctospirella Bed indicates that fossil hypericinoid pigments were more widespread in encrinids than previously known. Sedimentation conditions of the intraformational conglomerates, in which these crinoids were found, are discussed.