Triangulodus sp. A

Zhen, Yong Yi, Percival, Ian G. & Webby, Barry D., 2003, Early Ordovician Conodonts from Far Western New South Wales, Australia, Records of the Australian Museum 55 (2), pp. 169-220 : 216

Triangulodus sp. A

Fig. 29A–P

Material. 15 specimens (4 Sa, 5 Sb, 5 Sc, 1 Sd) from the Tabita Formation at Mount Arrowsmith , 64 specimens (11 Sa, 30 Sb, 21 Sc, 2 Sd) from unnamed dolomitic limestone unit at Koonenberry Gap .

Description. Only S elements are recognized for this species, characterized by having an open, slightly inflated basal cavity. Sa element symmetrical, tricostate, with a costa along the posterior margin, a broad anterior face, and a costa on each lateral side ( Fig. 29A–E ); cusp suberect, triangular in cross section. Sb element asymmetrical, bicostate, with an anterolateral costa on the inner lateral side, a posterolateral costa on the outer lateral side, and with broad anterior and posterior surfaces ( Fig. 29F–I ). Sc element asymmetrical, with a sharp costa along the anterior and posterior margins, and with the most laterally compressed base of all elements recognized; anterior costa inner laterally curved; a broad carina also developed on the inner lateral face ( Fig. 29J–M ). Sd element nearly symmetrical, with broad anterior and posterior margins, and with a sharp costa on each lateral face ( Fig. 29N–P ).

Remarks. This species, especially the Sa and Sc elements , somewhat resembles T. larapintinensis , but generally all elements are less laterally compressed with an open, slightly inflated basal cavity.

Figures

Fig.29.Triangulodus sp.A:A,B, Sa element,AMF124220,TAB1/8.1, A, basal view, B, posterolateral view; C–E, Sa element,AMF124221, Y4–8, C,D, posterolateral view, E, basal view; F, Sb element, AMF120483, Y4–2, inner lateral view; G,H, Sb element, AMF120485, C1613, G, upper, inner lateral view, H, upper, outer lateral view; I, Sb element,AMF120486, C1613, postero-inner lateral view; J,K, Sc element, AMF124222, C1613, J, basal view, K, inner lateral view; L,M, Sc element, AMF124223, C1613, L, inner lateral view, M, postero-inner lateral view; N–P, Sd element,AMF120487, M/A7, N, anterolateral view, O, posterolateral view, P, close up showing the fine striae. Scale bars 100 µm, unless otherwise indicated.