Table 1. Band assignments (cm⁻¹) for fossil and extant materials.

Band assignment [13], [15]	Squid [15]	Loligo sp. (NCSM, Sea of Japan)	Sepia officinalis [13]	Sepia sp. (NCSM 11403 & 11402)	M. mississipiensis MGS 1951
νOH	3479 (?) & 3426	3431	3421	3431	–
νasNH	3290	3292	3280	3395	3281
νsNH	3102	3085	3104	3091	3065
νasCH3	2962	2961	2966	2959	2956
νsCH2	2929	2933	2933	2931	2918
νasCH3	2880	2876	2884	2873	2849
νC = O,Amide I	1656	1656	1652	1657 & 1649	1656 & 1650
νC-N,C-N-H, Amide II +δN-H Amide II	1556	1533	1553	1541	1545
δCH2	1424	1433	1422	1437	1456, 1417
δCH and δC-CH3	1376	1375	1377	1376	1397
νC-N and δNH,Amide III	1314	1324 & 1304	1317	1306	–
δNH, Amide III	1262	1260	1262,1229, 1205	1260,1236, 1204	1231
νas C-O-C ring	1155	1157	1155	1159	1171
νC-O	1111	1113	1112	1115	–
νC-O	1069	1071	1073	1074	–
νC-O	1032	1033	1033	1032	1030
γCH3	948	949	948	947	–
γCH (C1axial) (β bond)	902	895	–	895	905
ρCH2	–	–	–	705	703
γNH (Amide V)	692	690	–	695	691