## 3 Results
### Thermal Desorption-Gas Chromatography-Mass Spectrometry of the Melanin from Ochroconis lascauxensis
Similar low abundance attained the series of alkylbenzenes (C\({}_{1}\)-C\({}_{12}\)) and some other compounds such as the peaks of hexadecanamide (101), octadecanamide (104), and octadecanamide (105), a few phenylalkanones (peaks 37, 44, 51), phenol (peak 16), and methylphenol (peak 21). In addition, 2-alkanones (C\({}_{10}\)-C\({}_{16}\)), and a few aldehydes contributed to the identified products. Figure 2B shows the chromatogram of the acid hydrolyzed melanin after thermal desorption at 300 \({}^{\circ}\)C. A list of the products evolved is shown in Table 2. The main differences between the untreated and the acid hydrolyzed melanin resides in the practical absence of carbohydrate and peptide pyrolysis products, the loss of alkylnitriles, alkylamides, and pyrazines, and the decreasing intensity of the fatty acids. Acid hydrolysis removes carbohydrates and most peptides and proteins, thus preventing the formation of these types of nitrogen-derived compounds. However, acid hydrolysis was not able to remove all fatty acids and the series from butanoic to octadecanoic acids were still present, but only hexadecanoic and octadecanoic acids (peaks 87 and 100) were abundant. The methyl esters of the hexadecanoic and octadecanoic acids (peaks 85, 95), as well as their ethyl esters (peak 101) and hydroxy fatty acids lactones (peaks 97 and 106), were identified as relatively important compounds. Apart from the fatty acids, there was a minor contribution of aromatic compounds: phenol, benzaldehyde, acetophenone, naphthalene, benzoic acid, biphenyl, benzophenone, phenanthrene, phenyl-fatty acids, and phenyl-ketones. The chromatogram of the hydrolyzed melanin evidenced as well a minor contribution of the series of alkanes and alkenes (C\({}_{6}\)-C\({}_{23}\)), alkylbenzenes (C\({}_{1}\)-C\({}_{17}\)), methylalkylbenzenes (C\({}_{2}\)-C\({}_{18}\)) (Table 2), and dibutyl- and bis-(ethylhexyl)-phthalates (peaks 81, 109) in Figure 2B. The presence of chlorine and sulfur derivatives (peaks 1, 2, 5, 63), and particularly of a few alkylthiophenes (peaks 18, 26, 36) in Table 2 were noticeable. Chlorine is coming from the hydrochloric acid used for the hydrolysis and sulfur derivatives are related with the percentage of sulfur in the melanin (0.5%) as reported elsewhere [19]. The production of alkylbenzenes and alkylthiophenes in the pyrolysis of fatty acids was already reported by [PERSON] [24,25]. Second Shot Pyrolysis-Gas Chromatography-Mass Spectrometry of the Melanin from Odtroconis lascauxensis  
For the second step, performed at 500 \({}^{\circ}\)C, the compounds detected were interpreted as fragments produced from the thermal degradation of larger macromolecules or structural units forming the core, once loosely held or volatile compounds have been previously removed at 300 \({}^{\circ}\)C.  
Figure 3A displays the chromatogram of the melanin pyrolyzed at 500 \({}^{\circ}\)C, which previously was subjected to thermal desorption at 300 \({}^{\circ}\)C. The pyrolysis products evolved at 500 \({}^{\circ}\)C are listed in Table 3.  
In the pyrogram of Figure 3A, the fatty acids were drastically reduced, due to the previous thermal desorption, as denoted the low intensity of the major peaks (99: hexadecanoic, 108: octadecenoic, and 109: octadecanoic acids). This was a clear effect of the previous thermal desorption at 300 \({}^{\circ}\)C. However, the first 300 \({}^{\circ}\)C step had a limited effect on the removal (pyrolysis) of proteins as denoted the identification of pyrrole, pyridine, indole and its alkyl derivatives (e.g., peaks 6, 11, 51, 60, 68), pyrrolopyrazines (peaks 97,98), diketodipyyrrole (peak 81) and the presence of nitriles (peaks 31, 34, 44, 92, 105, 107, 118, 119) and amides (peaks 110, 115, 116). As expected, due to the previous pyrolysis of polysaccharides at 300 \({}^{\circ}\)C, carbohydrates markers were almost absent.