Prioniodus Pander, 1856

Y Y Zhen, 2005, Revision of Two Prioniodontid Species (Conodonta) from the Early Ordovician Honghuayuan Formation of Guizhou, South China, Records of the Australian Museum 57, pp. 303-320 : 311-312

Prioniodus Pander, 1856

Type species. Prioniodus elegans Pander, 1856 .

Remarks. The type species of Oepikodus Lindström, 1955 , O. smithensis Lindström, 1955 , was originally proposed as a form species based on the oepikodiform elements ( Lindström, 1955, pl. 6, figs 1–3). Subsequently, Lindström (1971) considered Oepikodus as a junior synonym of Prioniodus, 1856 , and its type species, O. smithensis , along with Oistodus longiramis Lindström, 1955 to be parts of the revised multi-element species Prioniodus evae Lindström , which was also originally proposed as a form species based on the prioniodiform elements ( Lindström, 1955, pl. 6, figs 4–10). Hence Lindström (1971) defined P. evae as consisting of a trimembrate apparatus including prioniodiform, oepikodiform and oistodiform elements. However, Bergström & Cooper (1973, pp. 323–324) pointed out that “the apparatus of P. evae differs from that of P. elegans ”, the type species of Prioniodus , and “no element clearly homologous to the hibbardelliform element” existed in the latter. They further considered Oepikodus to be a subgenus of Prioniodus . This suggestion was formalized by Serpagli (1974). However, van Wamel (1974) and Lindström (in Ziegler, 1975) restored Oepikodus as a separate multi-element genus consisting of a trimembrate apparatus. Bergström (in Clark et al., 1981) and Stouge & Bagnoli (1999) categorized Oepikodus and Prioniodus as belonging to different families.

Serpagli (1974) and Lindström (in Ziegler, 1975) redesignated the form species P. evae Lindström, 1955 as the type species of Oepikodus , since the originally

[ Fig. 5 caption continued] … (P–R) Sd element, AMF126754, AFI997, (P) outer lateral view (IY53002), (Q) posterior view (IY53001), (R) inner lateral view (IY53003); (S) Sd element, AMF126755, AFI997, basal-posterior view (IY66006); (T) Sd element, AMF126756, AFI997, inner lateral view (IY66001); (U,V) Sd element, AMF126757, AFI993, (U) outer lateral view (IY66017), (V) anterior view (IY66016); (W–Y) Sd element, AMF126758, THH3, (W) upper view (IY58017), (X) outer lateral view (IY58019), (Y) inner lateral view (IY58018); (Z,AA) Sd element, AMF126759, AFI993, (Z) inner lateral view (IY66018), (AA) posterior view (IY66020). Scale bars 100 µm.

designated type species O. smithensis became a synonym of Prioniodus evae (see Lindström in Ziegler, 1975, p. 237). As correctly pointed out by van Wamel (1974, p. 74), the form species O. smithensis is not a junior synonym of the form species P. evae , and the form species O. smithensis must therefore remain as the type species of Oepikodus . Although O. smithensis has page priority among the three form species erected by Lindström in the same publication for three different genera, they ( O. smithensis Lindström, 1955 , P. evae Lindström, 1955 , and Oistodus longiramis Lindström, 1955 ) form the apparatus of a multi-element species, which was named as P. evae by Lindström (1971). With Lindström (1971) as the first reviser (see Article 24.2.2, ICZN of 1999 edition), O. evae ( Lindström, 1955) emend. Lindström (1971) is recognized as a valid and proper name of the species with this multi-element apparatus.

Following the definition of Oepikodus as trimembrate ( van Wamel, 1974) and then quadrimembrate (Bergström in Clark et al., 1981), Stouge & Bagnoli (1988) suggested that Oepikodus consisted of a seximembrate apparatus that could be distinguished from Prioniodus by lack of the Sa element. Albanesi (in Albanesi et al., 1998) concurred with this concept.

Oepikodus , as most recently revised by Nicoll & Ethington (2004), was defined as consisting of a septimembrate apparatus including pastinate Pa and Pb, makellate M and quadriramate S (Sa, Sb, Sc and Sd) elements. Prioniodus consists of a similar septimembrate apparatus that includes a triform alate Sa element, rather than a quadriform alate Sa element as in Oepikodus . Therefore, occurrence of the triform alate Sa element in the new species from the Honghuayuan Formation confirms its generic assignment to Prioniodus .