Scolopodus, Pander, 1856

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 : 252-253

Scolopodus ? oistodiformis An & Ding, 1985

Fig. 27A–I

Scolopodus rex oistodiform An & Ding, 1982 : pl. 1, fig. 9 (nomen nudum); An & Ding, 1985: 8, pl. 1, figs 16–18; An et al., 1985: pl. 8, fig. 5, pl. 10, figs 2–4; An, 1987: 187, pl. 7, figs 12, 24, 30; Gao, 1991: 140–141, pl. 6, fig. 20; Ding et al. in Wang, 1993: 205–206, pl. 14, figs 13–15; Zhao et al., 2000: 224, pl. 14, figs 1, 9.

Scolopodus rex Lindström. –Zhang, 1998c: 90–91, pl. 17, figs 5–8.

Scolopodus longibasis Ni in Ni & Li, 1987: 439, pl. 57, figs 47–50.

Material. Six specimens from three samples (see Tables 1–2).

Remarks. Scolopodus rex oistodiformis was first introduced into the literature as a nomen nudum by illustration only (An & Ding, 1982). Subsequently, An & Ding (1985) formally defined this subspecies as consisting of a bimembrate apparatus including an asymmetrical geniculate element and a symmetrical, short-based multicostate scolopodiform element. They indicated that the geniculate element was closely comparable with the form species S. rex var. paltodiformis Lindström, 1955a . Zhang (1998c) considered S. rex oistodiformis as a junior synonym of S. rex and included geniculate M, short-based scolopodiform P and long-based scolopodiform S elements with the S elements forming a symmetry transition series. In the recent revision of S. striatus, Tolmacheva (2006) regarded S. rex as a junior synonym of S. striatus , but rejected the specimens figured as S. rex by Zhang (1998c) from her revised multielement species, S. striatus . Therefore S.? oistodiformis is considered herein as representing a separate species as defined by Zhang (1998c). S. longibasis Ni in Ni & Li, 1987 is identical with the long-based S elements of this species from the Guniutan Formation of South China (Zhang, 1998c) and from the Dawangou Formation of the Tarim Basin ( Fig. 27D–I ). Therefore it is considered to be a junior synonym of S.? oistodiformis. In the Dawangou samples, S.? oistodiformis and S. striatus co-occur, and the short-based P and long-based S elements of S.? oistodiformis are difficult to differentiate from those of S. striatus . In particular, some of the longbased specimens referred to as the Sd element of S. striatus might likely belong to the S elements of S.? oistodiformis, which typically have a lesser number of costae, a longer base and a cusp varying from proclined to suberect ( Fig. 27D–I ).

Scolopodus ? oistodiformis shows close resemblance to S. subrex Ji & Barnes, 1994 , particularly the M elements which are nearly identical (see Ji & Barnes, 1994, pl. 19, figs 9–14), but S. subrex has S elements with a relatively shorter base (Ji & Barnes, 1994, pl. 19, figs 1–8), and the Pa element is rather distinctive with a very short base and a prominent notch on the basal margin (Ji & Barnes, 1994, pl. 19, fig. 15).

Figures

Figure 27. Scolopodus? oistodiformis An & Ding, 1985. A–C, M element; A–B, NIGP 153104, Nj294, posterior view (IY148-020), B, basal view (IY148-019); C, NIGP 153105, Nj295, posterior view (IY149-008). D–E, Sa element, NIGP 153106, Nj294, D, anterior view (IY148-023), E, lateral view (IY148-031); F–G, Sb element, NIGP 153107, Nj294, F, basal-inner lateral view (IY148-022), G, outer lateral view (IY148-021). H–I, Sc element, NIGP 153108, Nj294, inner lateral view (IY148-030), I, outer lateral view (IY148-031). Scale bars 100 µm.