Ulrichodina sp.

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

Ulrichodina sp. cf. simplex Ethington & Clark, 1982

Fig. 14M–O

Drepanodus sp. 3 Serpagli, 1974: 45 , pl. 10, fig. 7a–b, pl. 21,

fig. 15.? Ulrichodina ? simplex Ethington & Clark, 1982: 113 , pl. 13, figs.

3–4, 9.? Ulrichodina ? simplex .– Smith, 1991: 71, fig. 40d.? Ulrichodina n.sp. 3 Repetski, 1982: 56, pl. 26, fig. 7a–c, fig. 8H.

Material. A single specimen from limestone nodules within shales of the upper Yandaminta Quartzite at Mount Arrowsmith.

Remarks. Due to limited material, neither generic nor specific identification is certain. This specimen may well correspond to the Sa element of a Drepanoistodus species. However, based on its distinctive basal cavity shape and the notch on each side, it is tentatively ascribed to Ulrichodina . The specimen is a symmetrical, hyaline coniform unit with a laterally compressed, stout, erect cusp, having a distinctive, short, strongly posteriorly curved anticusp-like projection, which has a narrow but rounded anterior corner, and a distinct notch on the basal margin of both sides. It is nearly identical to a specimen referred to as Drepanodus sp. 3 from the San Juan Formation of the Argentine Precordillera ( Serpagli, 1974). However, it is about twice the size of the San Juan specimen, and has the anticusp-like projection at the anterobasal corner more strongly curved posteriorly.

Ethington & Clark (1982) doubtfully assigned Serpagli’s San Juan specimen to their new species,? Ulrichodina simplex , which was based on four elements from the Fillmore Formation of the Ibex area, Utah. The three figured type specimens are rather poorly preserved. The holotype is a very large element (about three times as large as the San Juan specimen), has a much weaker development of the notch on each side of the basal margin, and a more laterally compressed cusp with sharp anterior and posterior margins. Ulrichodina simplex was also reported from the E1 Paso Group ( Repetski, 1982), and from the Wandel Valley Formation of Greenland ( Smith, 1991). In all these occurrences, it is represented by just a few specimens. The figured Greenland specimen, even more doubtfully assigned to U. simplex , is an albid element, with a laterally flared buttress on each side, rather than exhibiting a notch deeply carved into the base, as in the Mount Arrowsmith specimen. ACKNOWLEDGMENTS. Fieldwork by YYZ & BDW at Mount Arrowsmith was undertaken with the support of the Australian Research Council (grant A39600788 to BDW). The study was also supported by a Research Fellowship to YYZ kindly provided by the Sydney Grammar School. John Paterson (Macquarie University) is thanked for providing some additional conodont material from a measured section in the Mount Arrowsmith area. IGP sampled the Koonenberry Gap section under the guidance of Kingsley Mills (Geological Survey of New South Wales). Barry Cooper (Primary Industry & Resources Department of South Australia) kindly made available additional Horn Valley Siltstone collections for comparative study. Gary Dargan (Geological Survey of New South Wales) assisted with acid leaching, residue separation and other laboratory work. Scanning electron microscope photographs were prepared in the Electron Microscope Unit of the Australian Museum; Sue Lindsay is thanked for providing helpful assistance with the SEM work. Helen Beare is thanked for kindly carrying loan material to and from Adelaide. We are grateful for detailed reviews provided by Bob Nicoll (Australian National University) and Guillermo Albanesi (CONICET, Cordoba, Argentina) which markedly contributed to our understanding of several species. IGP publishes with permission of the Director General, NSW Department of Mineral Resources. This is a contribution to IGCP Project no. 410: the Great Ordovician Biodiversification Event.

Figures

Fig. 14. A–K, Drepanoistodus basiovalis (Sergeeva, 1963): A,B, P element, AMF120351, Y4–2, A, outer lateral view, B, basal view; C, Sb element,AMF120352, M/A7, outer lateral view; D–F, P element,AMF120354,W5, D, outer lateral view, E, posterior view, F, inner lateral view; G, Sa element, AMF120356, M/A11-3, lateral view; H, P element, AMF120355, Y4–2, outer lateral view; I, Sc element, AMF120358, M/A11-2, inner lateral view; J, M element, AMF120357, Y4–2, anterior view; K, M element, AMF120353, A/M11–3, posterior view. L, Drepanoistodus sp., AMF120360, W5, outer lateral view. M–O, Ulrichodina sp. cf. simplex Ethington & Clark, 1982, AMF120359, W5, M,N, lateral views, O, basal view. Scale bars 100 µm.