Fissidentalium mawsoni (Ludbrook, 1956)

Fissidentalium mawsoni (Ludbrook, 1956) View in CoL

Figure 7C View FIGURE 7

Pattern description. Yellow fluorescence. 1–2 thin transverse bands, located near the centre and just above the anterior aperture of the shell.

Energy-dispersive X-ray Spectroscopy

The EDX results on Maoricolpus murrayanus (Table 1) include data from both fluorescing and non-fluorescing areas of the shell. Whilst in the EDX machine it was not possible to see the fluorescing area due to a lack of UV light source, and SEM images being rendered without colour. To minimise this issue, a fluorescent section marked prior to analysis was examined as closely as possible. Thus, the elemental spectrum results are a combination of both the fluorescing area and non-pigmented area and are not able to be separated outside of visual interpretations made from the elemental distribution maps ( Figure 8 View FIGURE 8 ).

EDX of the fossil shell M. murrayanus identified O, C, and Ca, which constitute the calcium carbonate of the shell, with Si (apparent concentration 4.80, 2.54 Wt% –i.e., weight percentage–, 1.6 At%) and Al (apparent concentration 1.70, 100 Wt%, 0.6 At%) as the only other elements of notable amounts. Na, Mg, S, Cl, K, Fe, and W are all also present in miniscule amounts (see Table 1). Visual examination of the distribution map ( Figure 8 View FIGURE 8 ) shows a weak correlation between the density of Si, and to a lesser extent Al, and the area of remaining pigmentation/fluorescence. There also appears to be less carbon at this location than there is in the surrounding area. Other recorded elements show no apparent difference in density between the fluorescent and non-fluorescent areas.

In comparison, the EDX of the modern shell, M. roseus , indicated that there were no levels of anything over 1At% (atomic percentage) except for the expected O (51.4 At%), C (36.9 At%), and Ca (11.2 At%). Na, S, Si, Cl, Fe, Mg, and Sr were present but in miniscule amounts. There was no apparent visual correlation in the elemental maps between the pigmented area and any of the identified elements (Supplementary Figure 2 View FIGURE 2 ).