Icriodus alternatus helmsi Sandberg and Dreesen, 1984

Day, Jed & Over, D. Jeffrey, 2002, Post-extinction survivor fauna from the lowermost Famennian of eastern North America, Acta Palaeontologica Polonica 47 (2), pp. 189-202 : 199

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).

Figures

Fig. 5. Digital images from scanning electron microscope of conodont P1 (Pa) elements from the Hanover Shale Member of the Java Formation, brachiopod bed approximately 1.4 m above the Frasnian–Famennian boundary at Glade Creek, Bartz Road, Wyoming County, New York. All × 60. A–C. Palmatolepis triangularis Sannemann, 1955. A, B. Lower view and inverse mirror−image of mold of upper surface of P1 (Pa) element, NYSM 15682. C. Inverse mirror−image of mold of upper surface of P1 (Pa) element, NYSM 15683. D–F. Icriodus alternatus alternatus Branson and Mehl, 1934. D, E. Upper and oblique outer views of broken P1 (Pa, I) element showing internal mold of posterior end, NYSM 15684. F. Upper view of P1 (Pa, I) element with missing inner posterior margin, NYSM 15685. G. Icriodus alternatus helmsi Sandberg and Dreesen, 1984, upper view of fractured and covered P1 (Pa, I) element, NYSM 15686 (specimen lost).