Drepanodus arcuatus Pander, 1856

Zhen, Yong Yi & Nicoll, Robert S., 2009, Biogeographic and Biostratigraphic Implications of the Serratognathus bilobatus Fauna (Conodonta) from the Emanuel Formation (Early Ordovician) of the Canning Basin, Western Australia, Records of the Australian Museum 61 (1), pp. 1-30 : 11

Drepanodus arcuatus Pander, 1856

Fig. 5A–F

Drepanodus arcuatus Pander, 1856: 20 , pl. 1, figs 2, 4–5, 17, 30,?31; Löfgren & Tolmacheva, 2003: 211–215, figs 2, 3A–C, E–H, 5K–V, 6M–U, 7H–N, 8A–G (cum syn.); Zhen et al., 2004: 52–53, pl. 3, figs 1–12; Zhen et al., in press a: fig. 5A–N (cum syn.).

Material. 95 specimens from three samples ( Table 1).

Remarks. Recently revised as having a septimembrate apparatus (Löfgren & Tolmacheva, 2003), D. arcuatus is a pandemic species widely distributed in various environments from inner shelf to slope (or basinal) settings with a long stratigraphic range from the late Tremadocian to Late Ordovician. It is a fairly common species in the Emanuel with specimens generally larger in comparison with those of other taxa. The cusp of the Sa element varies from proclined ( Fig. 5B ) to reclined ( Fig. 5A ), the Sd element has a twisted cusp and inwardly flexed anterobasal corner ( Fig. 5C, D ), the Pb element is characterized by having a strongly reclined cusp and a more or less square base in lateral view with basal margin curved into a right angle, and the Pa element bears a flared base with a shallower basal cavity ( Fig. 5F ). The symmetrical Sa element with a proclined cusp ( Fig. 5B ) is identical with the neotype and other illustrated specimens from western Russia and Sweden (Löfgren & Tolmacheva, 2003, fig. 3A, B, fig. 6O), and from the Honghuayuan Formation of Guizhou (Zhen et al., in press a, fig. 5B). The illustrated Sd, Pb and Pa elements are also comparable with those illustrated by Löfgren & Tolmacheva (2003) from Russia (fig. 3E–G) and Sweden (fig. 5O,V), and those from the Honghuayuan Formation of Guizhou (Zhen et al., in press a, fig. 5I, 5L, 5N).

Figures

Fig. 5.A–F, Drepanodus arcuatus Pander, 1856.All from sample WCB705/133.A,B, Sa element; (A), CPC39811, lateral view (IY126-002); (B), CPC39812, lateral view (IY126-003). C,D, Sd element; (C), CPC39813, inner lateral view (IY127-028); (D), CPC39814, inner lateral view (IY127-022).(E), Pb element, CPC39815, innerlateral view (IY126-001).(F), Pa element, CPC39816,outer lateral view (IY126-005). G–P, Drepanoistodus sp. cf. D. nowlani Ji & Barnes, 1994. (G), M element, CPC39817, WCB705/243, anterior view (IY129-005). H,I, Sa element; (H), CPC39818, WCB705/133, lateral view (IY126-004); (I), CPC39819, WCB705/133, lateral view (IY127-016). (J), Sb element, CPC39820, WCB705/133, inner lateral view (IY127-029). K,L, Sc element; (K), CPC39821, WCB705/133, outer lateral view (IY126-008); (L), CPC39822, WCB705/133, outer lateral view (IY129-027). (M), Sd element, CPC39823, WCB705/133, inner lateral view (IY127-030). N,O, Pa element; (N), CPC39824,WCB705/243, inner lateral view (IY129-025); (O), CPC39825,WCB705/243, outer lateral view (IY129-026). (P), Pb element, CPC39826, WCB705/243, outer lateral view (IY129-006). Scale bars 100 µm.