Trilobite eyes contained melanin

[Halichoeres]

This team of researchers determined the presence of eumelanin in trilobite ommatidia (eye subunits) by careful comparison with living and fossil crane flies. Melanin has not been observed in arthropod eyes before. You may recall that one line of evidence that was used to argue that the tully monster is a vertebrate was the presence of melanin in the eyes--this throws that out the window. It also suggests that trilobite eyes were mostly organic, rather than mineralized. Very cool paper.

Paper (paywall, but you know what to do if you want a pdf): https://www.nature.com/articles/s41586-019-1473-z