Prioniodus 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 : 204

Prioniodus sp. A

Fig. 21M–Q

Material. Four specimens (3 Pa, 1 Pb) from the Tabita Formation at Mount Arrowsmith.

Description. Both Pa and Pb elements have a robust, erect cusp with sharp anterior and posterior margins; Pb element with a more laterally compressed blade-like cusp, and short posterior and outer lateral processes, with four denticles on the former and a single denticle on the latter; the anterior process long, inner laterally curved, bearing more than ten denticles ( Fig. 21M,N ). Cusp of Pa element more or less triangular in cross section, with a sharp mid-costa along the outer lateral face, which extends basally into a long denticulate outer lateral process ( Fig. 21P,Q ); long denticulate posterior process bearing closely spaced denticles which are erect and laterally compressed; outer lateral process normal to the posterior process ( Fig. 21 O ), bearing over ten closely spaced denticles which are anteroposteriorly compressed, with tips slightly curved posteriorly; neither anticusp nor denticles developed at the anterobasal corner.

Remarks. The Pa element is well defined and is distinguished from those of other species of the genus by its long denticulate posterior and outer lateral processes. The Pb element of this species is characterized by a prominent cusp, and long denticulate anterior process. It shows some resemblance to the P element of Prioniodus sp. A McTavish, 1973 from the Emanuel Formation of the Canning Basin ( McTavish, 1973, pl. 2, fig. 4), but has an even longer anterior process with prominent denticles, and a much shorter outer lateral process.

Figures

Fig. 21. A–L, Prioniodus sp. cf. P. amadeus Cooper, 1981: A,B, P element, AMF120412, TAB1/78.2, A, outer lateral view, B, upper, inner lateral view; C,D, P element, AMF120413, TAB1/78.2, C, upper, antero-inner lateral view, D, postero-outer lateral view; E, Sb element, AMF120415, M/A7, inner lateral view; F, Sb element, AMF120416, M/A7, outer lateral view; G, Sc element, AMF120414, TAB1/78.2, lateral view;H,I, Sd element,AMF120417,TAB1/78.2, H, inner lateral view, I, posterior view; J,K, Sa element,AMF120418, M/A11-3, lateral views; L, M element, AMF124213, W/A11-5, anterior view. M–Q, Prioniodus sp.A: M,N, Pb element, AMF120420, M/A7, M, inner lateral view, N, anterior view; O, Pa element, AMF120419, Y4–2, outer lateral view; P, Pa element, AMF120422, Y4– 2, postero-outer lateral view; Q, Pa element, AMF120421, Y4–2, upper view. Scale bars 100 µm.