... Scanning Electron Microscopy/Energy Dispersive Spectrometry (SEM/ EDS) Analyses of A. nordenskjoeldi under SEM/EDS revealed a unique combination of morphological , ultrastructural and chemical traits; they are: (1, 2) chambered, longiconic conch; (3, 4, 5) thin microlaminated shell wall, having no nacreous layer; (6, 7) a central/or slightly sub-central , broadly expanded siphuncle; (8) notably large (0.6 shell diameter) septal foramen, 2–6 times wider than that of all other known cephalopods; (9, 10, 11) deep, thin, organic septa; (12, 13) thin suborthochoanitic septal necks; (14, 15) thin non-mineralized connecting rings; (16) inorganic-organic mural, epi-and hyposeptal cameral deposits; (17) hyposeptal cameral soft tissues; (18) lack of endosiphuncular deposits; (19, 20) lack of a rostrum and pro-ostracum; (21) irregular mineralization of the shell wall evidenced by the variable content of calcium (5.4% -27.8%); (22) inorganic-organic shell wall composition indicated by high content of nitrogen (up to 7. 8%) and additionally by lower (less than 1%) content of manganese, iron, nickel, copper, zinc, barium, thallium and lead (Figs 1A–1G, 2A–2C, 3, 4A–4C, 5A–5C and 6A–6G; S1, S2A, S2B, S3, S4A, S4B, S6A, S6B and S8A–S8H Figs; Table 1). The prismatic mural, epi-and hyposeptal cameral deposits have, in comparison with the shell wall, higher average values of calcium (24% and 16.6%, respectively), carbon (27.6% and 18. 4%), nitrogen (7.05% and 4. 7%), magnesium (0.9% and 0.4%), potassium (0.9% and 0.2%), approximately similar values of oxygen (55.2% and 59.9%) and strontium (0.2% and 0.2%), but lower average values of copper (0.1% and 0.5%), zinc (0.5% and 0.7%), and lead (0.2% and 0.4%) (Fig 6A–6H; Table 1). ...