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. 2021 Jan 14;9:e10703. doi: 10.7717/peerj.10703

Figure 9. Composition of the Liesegang rings resembling chromatophores in two Mesozoic coleoids.

Figure 9

(A) Millimetric sample of Dorateuthis syriaca, Cenomanian, Haqel (Lebanon). PIMUZ 51762. (B) Millimetric sample of Trachyteuthis hastiformis, Kimmeridgian, Rygol quarry, Painten (Germany). PIMUZ 51761. (C) Raman spectroscopy (using a 532-nm laser) of the circles in the Doratheutis sample, showing the so-called graphite (G) and defect (D) bands typical of organic materials preserved in sedimentary rocks. The bands identified by an asterisk are instrumental quasi-periodic ripples resulting from intense background luminescence (see Alleon et al. (2020) and references therein). (D) Diffractograms obtained for both samples, compared to references for minerals commonly associated with fossils. Phase identification confirms the phosphatic nature of these structures; only apatite is found in the Doratheutis sample, quartz and calcite from the sedimentary matrix are found in association with apatite in the Trachyteuthis sample. Scale bars, 1 mm.