Zhen & Nicoll: Canning Basin Serratognathus bilobatus Fauna 
27 
have a broad convex outer face and a concave inner face with 
a thin anterior margin curved inward. The lateral costa is 
weak, and may even be represented only as a broad carina 
on the inner side of the Pa element (Zhen et al., 2004, pi. 
1, figs 1, 3) which is comparable with those illustrated by 
Stouge & Bagnoli (1988, pi. 16, fig. 2)and those from the 
Emanuel Formation (Fig. 16F-P). However, the lateral costa 
is plainly evident in the Pb element (Zhen et al., 2004, pi. 1, 
fig. 4). Similar variations among the P elements of T. comptus 
were also observed in the material from the St. George Group 
(Ji & Barnes, 1994). Therefore, Tropodus is defined herein 
as consisting of a geniculate M element, a series of highly 
variable S elements (in respect to the number of the costae), 
and acodiform P elements with a lateral costa on the inner 
side varying from weak to well developed. 
Tropodus australis (Serpagli, 1974) 
Fig. 16A-P 
Walliserodus australis Serpagli, 1974: 89-91, pi. 19, figs 
5a-10c, pi. 29, figs 8—15, text-figs 23, 24. 
Tropodus australis (Serpagli).—Albanesi et al., 1998: 151, 
pi. 13, figs 12-18. 
Tropodus comptus australis (Serpagli).—Stouge & Bagnoli, 
1988: 141,142, pi. 16, figs 3-5; Lofgren, 1993: fig. 9: o, s, 
t; Lehnert, 1993: pi. 4, fig. 5; Lehnert, 1995: 129, 130. 
Acodus comptus (Branson & Mehl, 1933).—Zhen et al., 
2004: 50, 51, pi. 1, figs 1-19. 
Scolopodus ?rex Lindstrom.—Percival et al., 1999: 13, fig. 
8.9. 
Tropodus ?sweeti (Serpagli).—Percival et al., 1999: 13, 
fig. 8.10. 
Material. 190 specimens from three samples (Table 1). 
Remarks. Specimens from the Emanuel Formation are 
identical with those recovered from the Hensleigh Siltstone 
of central New South Wales (Zhen et al., 2004, pi. 1, figs 
1-19). Stouge & Bagnoli (1988) regarded W. australis as a 
subspecies of T. comptus. In the Emanuel Formation samples, 
only one species of Tropodus, T. australis is represented, 
exhibiting similar variation of the S elements (Fig. 16C-K) 
as was documented by Serpagli (1974), and the P elements 
(Fig. 16F-P) that are comparable with those described by 
Stouge & Bagnoli (1988) from the Cow Head Group of 
Newfoundland. 
Tropodus australis differs from typical T. comptus of the 
North American Mid-continent (Kennedy, 1980; Ethington 
& Clark, 1982; Fanding & Wesrop, 2006) mainly in having 
a strongly laterally compressed, muti-costate (Sc) element. 
Fanding & Westrop (2006) documented T. comptus from 
the Fort Cassin (Early Ordovician, Floian) of northeastern 
New York, and defined it as consisting of a septimembrate 
apparatus including S, M and P elements, and also illustrated 
a scandodiform element as representing the Sc position (see 
Fanding & Westrop, 2006, fig. 6.15). In the study of conodont 
faunas from the Jefferson City and other equivalent units in 
Oklahoma (Kindblade), Ethington (2009, per. com.) recog¬ 
nized the possible P elements of T. comptus and noticed their 
considerable difference from those of T. australis illustrated 
herein from the Emanuel Formation. He suggested that 
elements of T. australis tended to be heavier whereas those 
of T. comptus were more subdued. 
Acknowledgments. Study by YYZ was partially supported by 
the CAS/SAFEA International Partnership Program for Creative 
Research Teams. Scanning electron microscope photographs 
were prepared in the Electron Microscope Unit of the Australian 
Museum. Dr Ian Percival is thanked for carefully reading and 
helping with linguistic expression on an early version of the 
manuscript. G.S Nowlan, R.L. Ethington and S.A. Leslie are 
thanked for their careful and constructive reviews of the manu¬ 
script. This is a contribution to IGCP Project 503: Ordovician 
Palaeogeography and Palaeoclimate. 
References 
Albanesi, G.L., M.A. Hunicken & C.R. Barnes, 1998. Bioe- 
stratigraffa, biofacies y taxonomia de conodontes de las 
secuencias ordovfcicas del Cerro Porterillo, Precordillera central 
de San Juan, R. Argentina. Actas de la Academia Nacional de 
Ciencias 12: 1-249. 
An, T.X., 1981. Recent progress in Cambrian and Ordovician 
conodont biostratigraphy of China. Geological Society of 
America Special Paper 187: 209-226. 
An, T.X., 1987. Early Palaeozoic conodonts from South China. 
Peking University Publishing House, Beijing, 238 pp. (in 
Chinese with English abstract). 
An, T.X., & L.S. Ding, 1982. Preliminary studies and correlations 
on Ordovician conodonts from the Ningzhen Mountains, China. 
Acta Petroleum Sinica 3(4): 1-11 (in Chinese). 
An, T.X., & L.S. Ding, 1985. Ordovician conodont biostratigraphy 
in Hexian, Anhui Province. Geological Review 31: 1-12. 
An, T.X., G.Q. Du & Q.Q. Gao, 1985. Ordovician conodonts from 
Hubei. Geological Publishing House, Beijing, 64 pp. (in Chinese 
with English abstract). 
An, T.X., G.Q. Du, Q.Q. Gao, X.B. Chen & W.T. Li, 1981. 
Ordovician conodont biostratigraphy of the Huanghuachang 
area of Yichang, Hubei. In Selected Papers of the First 
Symposium of the Micropalaeontological Society of China, 
Micropalaeontological Society of China, ed., Science Press, 
Beijing, 105-113 (in Chinese). 
An, T.X., F. Zhang, W.D. Xiang, Y.Q. Zhang, W.H. Xu, H.J. Zhang, 
D.B. Jiang, C.S. Yang, L.D. Lin, Z.T. Cui & X.C. Yang, 1983. The 
Conodonts of North China and the Adjacent Regions. Science 
Press, Beijing, 223 pp. (in Chinese with English abstract). 
An, T.X., & S.C. Zheng, 1990. The conodonts of the marginal areas 
around the Ordos Basin, north China. Science Press, Beijing, 
199 pp. (in Chinese with English abstract). 
Bagnoli, G., S. Stouge & M. Tongiorgi, 1988. Acritarchs and 
conodonts from the Cambro-Ordovician Furuhall (Kopingsklint) 
Section (Oland, Sweden). Revista Italiana di Paleontologia e 
Stratigrafia 94(2): 163-248. 
Balfour, F.M., 1880-1881. A treatise on Comparative Embryology. 
Two Volumes. Macmillan & Co., London. 
Bergstrom, S.M., 1988. On Pander’s Ordovician conodonts: dis¬ 
tribution and significance of the Prioniodus elegans fauna in 
Baltoscandia. Senckenbergiana lethaea 69: 217-251. 
Bergstrom, S.M., A. Lofgren & J. Maletz, 2004. The GSSP of 
the second (upper) stage of the Lower Ordovician Series: 
Diabasbrottet atHunneberg, Province of Vastergotland, south¬ 
western Sweden. Episodes 27(4): 265-272. 
Branson, E.R., & M.G. Mehl, 1933. Conodont studies. University 
of Missouri Studies 8: 1-349. 
Brock, G.A., & L.E. Holmer, 2004. Early Ordovician lingulate 
brachiopods from the Emanuel Formation, Canning Basin, 
Western Australia. Memoir of the Association of Australasian 
Palaeontologists 30: 113-132. 
Brown, I.A., 1964. An Ordovician cystoid (Pelmatozoa, 
Echinodermata) from Western Australia. Proceedings of the 
Royal Society of Western Australia 47: 3-7. 
