Pseudooneotodus mitratus ( Moskalenko, 1973 )

Zhen, Yong Yi, 2011, Middle to Late Ordovician (Darriwilian-Sandbian) Conodonts from the Dawangou Section, Kalpin Area of the Tarim Basin, Northwestern China, Records of the Australian Museum 63 (3), pp. 203-266 : 247

Pseudooneotodus mitratus ( Moskalenko, 1973)

Fig. 23M–N

Ambalodus mitratus mitratus Moskalenko, 1973: 86 , pl. 17, figs 9–11.

Ambalodus mitratus nostras Moskalenko, 1973: 87 , pl. 17, figs 12–14,?15.

Pseudooneotodus mitratus (Moskalenko) .– Orchard, 1980: 25, pl. 3, figs 35, 42; Nowlan & Barnes, 1981: 23, pl. 2, figs 17–19; Nowlan, 1983: 667, pl. 3, figs 17, 21; Chen & Zhang, 1989: pl. 4, fig. 29; Pohler & Orchard, 1990: pl. 6, fig. 12; Dzik, 1994: 55, pl. 11, fig. 7; Zhen & Webby, 1995: 285, pl. 4, figs 16–17 (cum syn.); Zhang, 1998c: 85, pl. 14, fig. 12; Zhen et al., 1999: fig. 9.14–9.15; Leslie, 2000: 1139, fig. 5.37 (cum syn.); Sweet, 2000: fig. 9.7; Pyle & Barnes, 2001: 1396, 1398, pl. 2, fig. 13; Zhen et al., 2003a: fig. 6Q; Zhen et al., 2004b: fig. 9A; Zhen & Pickett, 2008: 79, fig. 9A–B (cum syn.).

Pseudooneotodus mitratus mitratus (Moskalenko) .–Zhao et al., 2000: 219, pl. 43, figs 19, 23.

Pseudooneotodus mitratus nostras (Moskalenko) .–Zhao et al., 2000: 219, pl. 43, figs 20–22, 24–25.

Material. Nine specimens from five samples (see Tables 1–2).

Remarks. This species, characterized by a trilobate basal outline, is a very minor component of the Dawangou fauna, comparable to its rarity in various faunas from New South Wales (Zhen & Webby, 1995; Zhen et al., 1999; Zhen et al., 2003a; Zhen et al., 2004b; Zhen & Pickett, 2008). Nowlan & Barnes (1981) and Nowlan (1983) regarded the two subspecies originally erected by Moskalenko (1973), A. mitratus mitratus and A. mitratus nostras , as constituent elements of a single species apparatus, and recognized a symmetry transition series among its elements. Although P. mitratus was a widely distributed species, its relative rarity in many faunas has hindered a formal reconstruction of its species apparatus in the literature. From our experience, the two morphotypes represented by Moskalenko’s (1973) two subspecies are often found co-occurring, but forms with nodes on the upper surface are much rarer and have not been recovered in the Dawangou samples.

The broad-conical morphotype of Pseudooneotodus triangulu s Chen & Zhang, 1984b is similar to P. mitratus in having a triangular outline in upper view, but the former species has the three processes more extended with a tendency to form a secondary ridge splitting from the posterior process (Chen & Zhang, 1984b, pl. 2, figs 25–26).

Figures

Figure 23.A–B, Venoistodus balticus Löfgren, 2006. M element; A, NIGP 153052, Nj296, posterior view (IY158-034); B, NIGP 153053, Nj296, posterior view (IY158-032). C–E, Protopanderodus liripipus Kennedy, Barnes & Uyeno, 1979. C–D, P element (low based); C, NIGP 153054, Nj406, inner lateral view (IY161-013); D, NIGP 153055, Nj406, outer lateral view (IY161-014). E, Sa element, NIGP 153056, Nj406, lateral view (IY155-010). F–L, Protopanderodus sp. F–G, Sa element, NIGP 153057, Nj297, lateral views (IY150-027, IY150-026). H–I, Sc element; H, NIGP 153058, Nj297, inner lateral view (IY150-028); I, NIGP 153059, Nj297, inner lateral view (IY150-029). J–L, Sb element, NIGP 153060, Nj296, J, outer lateral view (IY149-032), K, inner lateral view (IY149-031), L, basal view (IY149-030). M–N, Pseudooneotodus mitratus (Moskalenko, 1973). Pa element; M, NIGP 153061, Nj375, upper view (IY159-022); N, NIGP 153062,AFT-X-K13/44, upper view (IY164-029). O–P, Spinodus spinatus (Hadding, 1913). Sc element; O, NIGP 153063, Nj406, outer lateral view (IY161-001); P, NIGP 153064, Nj406, inner lateral view (IY161-002). Scale bars 100 µm.