Baltoniodus prevariabilis ( Fåhraeus, 1966 )

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 : 216

publication ID	https://doi.org/ 10.3853/j.0067-1975.63.2011.1586
persistent identifier	https://treatment.plazi.org/id/03CCEB77-FFDD-637F-FFE9-F97297BFF943
treatment provided by	Felipe
scientific name	Baltoniodus prevariabilis ( Fåhraeus, 1966 )
status

Treatment

Baltoniodus prevariabilis ( Fåhraeus, 1966)

Fig. 5H–K, M–P View Figure 5 ,?R

Prioniodus prevariabilis Fåhraeus, 1966: 29 , pl. 4, fig. 5a–b; Bergström, 1971: 146, pl. 2, fig. 1.

Prioniodus (Baltoniodus) prevariabilis prevariabilis Fåhraeus. – Löfgren, 1978: 87, pl. 12, figs 37–43 (cum syn.).

Baltoniodus prevariabilis Fåhraeus. – Lindström, 1971: 56 partim; An & Ding, 1982: pl. 5, figs 1–3, 7; An et al., 1985: pl. 7, figs 15, 18–19, pl. 16, figs 1–13; An, 1987: 127–128, pl. 20, figs 21–25, pl. 21, figs 1–7; Chen & Zhang, 1989: pl. 1, figs 10–14; Gao, 1991: 127, pl. 9, figs 1–3, 6; Ding et al. in Wang, 1993: 163, pl. 26, figs 1–17; Dzik, 1994: 82, pl. 18, figs 17–22, text-fig. 14b; Bednarczyk, 1998: pl. 1, figs 9–10, 12–13; Zhang, 1998c: 54, pl. 3, figs 1–8; Zhao, et al., 2000: 189, pl. 34, fig. 15, pl. 39, figs 1–6; Viira, 2011: fig. 6D–F, H, K, M–N, Q–S.

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

Remarks. Prioniodus prevariabilis was erected as a form species with the only figured specimen (holotype) exhibiting straight, denticulated posterior and outer lateral processes and a denticulated, inner laterally deflected anterior process ( Fåhraeus, 1966, pl. 4, fig. 5a–b). It represents the ambalodiform element in the multielement species apparatus that was first proposed by Löfgren (1978) to include the oistodiform (M), trichonodelliform (Sa herein), belodiform (Sb herein), tetraprioniodiform (Sd herein), amorphognathiform (Pa herein) and ambalodiform (Pb herein) elements. The cordylodiform (Sc herein) was also included in the species apparatus to form a septimembrate apparatus (An & Ding, 1982; An et al., 1985; Zhang, 1998c). Specimens referable to B. prevariabilis are rare in the Dawangou samples, and only Sa, Sc, Pa and Pb elements of this species are recovered from the Kanling Formation and the upper part of the Saergan Formation. The Sa element is alate with a long denticulate posterior process and a denticulate, downward-extending lateral process on each side ( Fig. 5H–I View Figure 5 ); the Sc element is bipennate with a long denticulate posterior process and a long, adenticulate anticusp-like anterior process ( Fig. 5O–P View Figure 5 ); the Pa element has low and long denticulate posterior and anterior processes ( Fig. 5J–K View Figure 5 ), and the Pb element displays a long denticulate, inner laterally curved, and strongly downwardextending anterior process ( Fig. 5M–N View Figure 5 ). These specimens are comparable with those documented from Jämtland of northern Sweden ( Löfgren, 1978) and from the Guniutan Formation of South China (Zhang, 1998c).

Several specimens recovered from the upper part of the Dawangou Formation are assigned to Baltoniodus sp. A ( Fig. 5D–G View Figure 5 ). It is characterized by the Pa element ( Fig. 5G View Figure 5 ) having the straight anterior and outer lateral processes adjoining at approximately right angles, and a Pb element ( Fig. 5E View Figure 5 ) with an inner laterally deflected anterior process and a posteriorly curved outer lateral process, which are remarkably different from that of B. prevariabilis . The denticulate lateral processes of this species are also higher and more laterally extended ( Fig. 5D View Figure 5 ) compared with B. prevariabilis .

Kingdom	Animalia
Phylum	Chordata
Class	Conodonta
Order	Conodontophorida
Family	Balognathidae
Genus	Baltoniodus