Crystal Creature

Abstract

An agglutinated animal (or possibly protist) of the Late Proterozoic Clemente Formation biota cemented an array of tourmaline crystals (trigonal prisms; schorl/dravite composition) to its dorsal surface, presumably as ballast, in the earliest known case of an agglutinated animal. Quantitative confirmation of the spatial association (clustering) of the tiny crystals is demonstrated here by means of Kappa (K) value analysis. This discovery of this Proterozoic “crystal creature” reveals both the earliest known case of agglutination, the earliest known case of monomineralogic agglutination, and the earliest known bioaccumulation of tabular crystals of the same mineral. This case compares to the preferential selection of ilmenite to form an agglutinated exoskeleton in the Cambrian agmatan Volborthella. It also compares to the preferential selection of muscovite flakes to form the agglutinated Cambrian worm tube Onuphionella. Agglutinated dorsal skeletons of the Proterozoic and Early Cambrian utilized selected mineral types, including white mica, ilmenite, anatase, and tourmaline. All of these minerals potentially afford protection from UV-B radiation, and may have been deployed on the dorsal surfaces of these early animals to serve as sunscreen.

That’s how fossil hunting is: It takes over, like a hunger, and nothing else matters but what you find. And even when you find it, you still start looking again the next minute, because there might be something even better waiting.

Tracy Chevalier