Protoprioniodus yapu Cooper, 1981

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 : 210

Protoprioniodus yapu Cooper, 1981

Fig. 24A–D

Protoprioniodus yapu Cooper, 1981: 178 , pl. 30, figs. 3–5, 8, 9, 11, 13.

Protoprioniodus costatus An, 1987: 174 , partim only, pl. 14, figs. 1, 4, pl. 16, fig. 25.

? Protoprioniodus yapu .– An, 1987, pl. 16, fig. 27.

Protoprioniodus costatus .–Ding et al., in Wang, 1993: 197, pl. 14, fig. 27.

Protoprioniodus yapu .–Ding et al., in Wang, 1993, pl. 15, figs. 10, 12.

Protoprioniodus aranda .–Johnston & Barnes, 2000: 42, partim only pl. 6, fig. 22.

Material. Seventeen specimens (5 Pb, 10 M, 2 doubtful S) from the Tabita Formation at Mount Arrowsmith.

Remarks. Nicoll (2002, pers. comm.) indicated that Protoprioniodus yapu may belong to part of the species apparatus of either P. nyinti or P. aranda (both transferred to the new genus Cooperignathus herein). As P. yapu is relatively rare in the Tabita Formation, Cooper’s (1981) definition is retained herein pending further study of the type material from the Horn Valley Siltstone.

In erecting P. yapu, Cooper (1981) illustrated two morphotypes of the P elements , both of which are highly modified pastinate units with a prominent cusp. The paratype ( Cooper, 1981, pl. 30, fig. 11) with rudimentary denticulate outer lateral processes is here designated as the Pa element . The holotype ( Cooper, 1981, pl. 30, fig. 9) lacks an outer lateral process, and is assigned to the Pb position ( Fig. 24B–D ). The M element is characterized by having a strongly inner laterally recurved cusp and an adenticulate, long outer lateral process, and apparently lacks an anticusp or inner lateral process ( Fig. 24A ). The strongly laterally compressed S elements (not identified with certainty at Mount Arrowsmith) have a strong mid-costa on the innerlateral face.

Protoprioniodus was distinguished by An (1987) from Oelandodus van Wamel, 1974 by having a prominent ridgelike costa above the basal margin. Comparison of the two species originally ascribed to Oelandodus shows that the type species, O. elongatus ( Lindström, 1955) , apparently lacks this feature, while its presence in O. costatus van Wamel, 1974 justifies An’s (1987) reassignment of this species to Protoprioniodus . The P elements of P. costatus and P. yapu are similar in morphology, but their S and M elements are easily distinguished. The S element of P. costatus shows some resemblance to the S elements of C. nyinti ; both have a tricostate cusp, costae extending basally to a lateral process on each side, and a long posterior process. The M element has a long pointed anticusp, straight basal margin and a strongly outer laterally recurved cusp. On this basis, the P, S and M elements referred to P. costatus by An (1987) from China are identical with those of P. yapu , rather than conspecific with the Swedish type material of P. costatus .

Figures

Fig. 24. A–D, Protoprioniodus yapu Cooper, 1981: A, M element, AMF120448, M/A7, posterior view; B,C, Pb element, AMF 120449, Y4–2, B, outer lateral view, C, inner lateral view; D, Pb element,AMF120450, M/A7, outer lateral view. E,F, Oneotodus sp.: E, AMF120451, M/A11-3, posterolateral view; F, AMF 124226, C1612, inner lateral view. Scale bars 100 µm.