Post-extinction survivor fauna from the lowermost Famennian of eastern North America Author Day, Jed Author Over, D. Jeffrey text Acta Palaeontologica Polonica 2002 2002-12-31 47 2 189 202 journal article 1732-2421 Icriodus alternatus helmsi Sandberg and Dreesen, 1984 Fig. 5G . Icriodus alternatus helmsi ; Sandberg and Dreesen 1984: 159 , pl. 2: 1–4, 6–7. Remarks .—The P 1 (Pa, I) element of Icriodus alternatus helmsi is characterized by alignment of the cusp with the innerlateraldenticles.Specimensinwhichthemedialdenticles are absent commonly occur in the Lower Pa. triangularis Zone through Middle Pa. crepida Zone ( Sandberg and Dreesen 1984 ).