Extended Data Fig. 4: ToF-SIMS images and spectra from a compound eye of a fossilized crane-fly (specimen MHM-18-6a).
From: Fossil insect eyes shed light on trilobite optics and the arthropod pigment screen
a–d, Positive-ion images representing calcium carbonate (Ca2O+ m/z 96, Ca2O2+ m/z 112, Ca2O2H+ m/z 113, Ca3O2+ m/z 152 and Ca3O3+ m/z 168) (a) and a nitrogen-containing fragment (C3H8N+ m/z 58) (b), together with a two-colour overlay image of these ions (c) in which green represents the organic compound and red calcium carbonate, and the total ion image (d) with selected regions of interest (ROIs) marked in green (corneal facet walls) and red (ommatidial lenses). e, f, Positive-ion spectra generated from the ROIs indicated in d, representing corneal facet walls (e) and ommatidial lenses (f). g–j, Images of negative ions representing eumelanin (C4H− m/z 49, C3N− m/z 50, C3NO− m/z 66, C6H− m/z 73, C5N− m/z 74 and C8H− m/z 97) (g) and oxygen (O− m/z 16) (h), together with a two-colour overlay image of these ions (i) in which green represents eumelanin and red oxygen, and the total ion image (j) with selected ROIs marked in green (corneal facet walls) and red (ommatidial lenses). k, l, Negative-ion spectra generated from the ROIs indicated in j, representing corneal facet walls (k) and ommatidial lenses (l). Data are representative of six independent measurements.
