Correction: Unravelling the mystery of "Madagascar copal": Age, origin and preservation of a Recent resin.

[This corrects the article DOI: 10.1371/journal.pone.0232623.].

Fig 3 appears in black and white rather than in color. Please see the correct Fig 3 here. The publisher apologizes for the error.

Fig 3

FTIR analyses comparing the differences between resin, copal and amber produced by Hymenaea spp. and Canarium madagascariensis.

(A) FTIR analyses of the samples in order to identify the tree-resin producer of “Madagascar copal”, include (see Table 1): Canarium madagascariensis and two samples of “Madagascar copal” (CM01 and CM02), two samples of resin from H. verrucosa branches (RHvA01-R1 and RHvA02-R0). (B) Malagasy H. verrucosa analyses: FTIR analyses that show the comparison between the results of A and other resin, copal and amber produced by Hymenaea ssp. The analyses include samples of Canarium madagascariensis (RMCR-01), “Madagascar copal” (CM01), resin from H. verrucosa branch, (RHvA01-R1), resin from H. verrucosa of the Andranotsara pit Q1, found in A horizon A (CM05-Q1) and in the sub-horizon B1 (CM06-Q1), and resin pieces of H. verrucosa of the Antampolo pit Q2, found in A horizon (CM03-Q2) and in sub-horizon B1 (CM4-Q2). (C) Neotropical Hymenaea spp. resin and amber analyses: resin from “copal of Colombia”, (CCS01), Miocene Mexican amber (AMS01), Miocene Dominican amber (AD-03) and (AD-04), and Miocene Ethiopian amber (EA-01). Diterpenic resin/copal has some characteristic vibrational group frequencies: characteristic is a low intensity of absorption band at 3080 cm-1 that is absent from triterpenoid resin/copal and that corresponds to v (= C-H), intensity absorption band at 2937–2929 cm-1 corresponds to vas(C-H), CH3, CH2 (methylene group), intensity band at 2874–2844 cm-1 corresponds to vs (C-H), CH3, CH2 (methyl group), intensity bands at 1718 cm-1, 1694 cm-1, and 1644 cm-1 correspond to v (C = O), intensity band at 1446 cm-1 corresponds to δas (CH3), intensity band at 1386 cm-1 corresponds to δs (CH3), and intensity band at 888 cm-1 corresponds out of plane δ (CH2) of the exomethylene functionality C8-C20. “Madagascar copal” and “East African Copal” can be differentiated from “Western African Copal” by the linear slope of the spectra in the case of the resin/copal of West Africa and the intensity of 3411–3422 cm-1 that corresponds to v (OH) of the East African copal. It is possible to differentiate between amber and copal by observing the exocyclic methylene bands at 3048, 1642 and 887 cm-1. In the case of copal, the first two bands are not intense, but they are clearly observed, and the band of 887 cm-1 is very intense. In the case of ambers, the bands are absent or of very weak intensity.