Protopanderodus graeai ( Hamar, 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 : 239-243

publication ID	https://doi.org/ 10.3853/j.0067-1975.63.2011.1586
persistent identifier	https://treatment.plazi.org/id/03CCEB77-FFF4-635A-FCC2-FCEE9622F8DD
treatment provided by	Felipe
scientific name	Protopanderodus graeai ( Hamar, 1966 )
status

Treatment

Protopanderodus graeai ( Hamar, 1966)

Fig. 21A–V View Figure 21

Acontiodus rectus Lindström. – Hamar, 1964: 258, pl. 1, figs 10, 12, 13, 17, text-fig. 4a–b.

Acodus graeai Hamar, 1966: 47 , pl. 3, figs 11–14, text-fig. 3.5.

Protopanderodus graeai (Hamar) .– Löfgren, 1978: 93–94, pl. 3, figs 19–25, text-fig. 31K–M (cum syn.); Mellgren & Eriksson, 2006: 105–106, figs 9V–BB, 12 (cum syn.).

Protopanderodus parvibasis Löfgren, 1978: 93 , pl. 3, figs 11–18, text-fig. 31D–F (cum syn.); Mellgren & Eriksson, 2006: 104–105, figs 9O–U, 11 (cum syn.).

Protopanderodus robustus (Hadding) .–Wang, 2001: 356, pl. 1, figs 3–4.

Material. 1249 specimens from 18 samples (see Tables 1–2).

Diagnosis. A species of Protopanderodus with a septimembrate apparatus; all the elements having an erect or suberect cusp and a short, non-expanded base, except for the Sb element bearing a longer base; M element with acostate anterior and posterior faces; S and P elements bearing a sharp posterior margin and a postero-lateral costa on each side, except for the strongly asymmetrical Sc element only having a sharp postero-lateral costa on the inner lateral side; basal margin straight or gently arched except for the Pb element.

Description. M element scandodiform, antero-posteriorly strongly compressed; cusp suberect in posterior or anterior view and curved posteriorly, with sharp inner and outer lateral margins; anterior face smooth and gently convex; posterior face less convex, varying from smooth to bearing a broad carina; basal margin straight ( Fig. 21A–C View Figure 21 ).

( Figure 18 View Figure 18 caption, continued from facing page)… O, NIGP 153013, Nj296, inner lateral view (IY149-025); P, NIGP 153014, Nj296, outer lateral view (IY149-026). Q–S, Sd element; Q–R, NIGP 153015, AFT-X-K13/13, Q, lateral view (IY168-016), R, basal view (IY168-017); S, NIGP 153016, Nj378, upper view showing cross section of cusp (IY160-012). T–V, W, Pa element; T, NIGP 153017, AFT-X-K13/13, outer lateral view (IY168-012); U–V, NIGP 153018, Nj295, U, outer lateral view (IY149-022); V, inner lateral view (IY149-021); W, NIGP 153019, Nj384, outer lateral view (IY162-014), tentatively assigned to this species. X–Y, Pb element; X, NIGP 153020, AFT-X-K13/13, inner lateral view (IY168-009); Y, NIGP 153021, AFT-X-K13/13, outer lateral view (IY168-010). Scale bars 100 µm, unless otherwise indicated.

Sa element symmetrical; cusp suberect with a sharp posterior margin and a posterolateral costa on each side ( Fig. 21D–G View Figure 21 ). Sb element like Sa, but asymmetrical, and often with a longer base, and with costa on the outer lateral face more strongly developed and located more towards posterior margin ( Fig. 21H–J View Figure 21 ). Sc element strongly asymmetrical with a convex, smooth outer lateral face and a less convex inner lateral face; cusp suberect with a sharp posterior margin and a sharp posterolateral costa on the inner lateral face ( Fig. 21K–P View Figure 21 ). Sd element nearly symmetrical, with a sharp posterior margin and a sharp posterolateral costa on each side; similar to Pa element, but less asymmetrical ( Fig. 21Q–R View Figure 21 ).

Pa element asymmetrical, with a convex outer lateral face and a less convex (or even concave) inner lateral face to form sharp anterior and posterior margins, and with a gently arched basal margin; cusp suberect with a strongly developed sharp postero-lateral costa on the outer lateral face and a only weakly developed costa on the inner lateral face, costa on the outer lateral face more towards posterior margin ( Fig. 21S–T View Figure 21 ). Pb element slightly asymmetrical; cusp erect with a sharp posterior margin and a sharp postero-lateral costa on each side; basal margin strongly curved with anterior portion and the posterior portion nearly normal to each other, forming a rectangular outline of the base ( Fig. 21U–V View Figure 21 ).

Remarks. In their recent revision of this species, Mellgren & Eriksson (2006) referred the strongly asymmetrical element (herein designated as Sc) to the M position, and split the Sb element defined herein into Sb1, Sb2, and Sc elements. They also assigned the M element (as defined herein) to the M element of P. cooperi (referring to it as P. robustus ; see Mellgren & Eriksson, 2006, fig. 13E), and to the M element of P. parvibasis .

The Sc element of P. graeai is morphologically more closely related to the other S and the P elements of this species (by its size and location of the postero-lateral process on the inner surface), and is also rather different from the M elements recognized in other species of Protopanderodus , which are generally larger than the P and S elements and strongly compressed antero-laterally. The M element of P. graeai defined herein is comparable with the M element of P. cooperi , but the latter characteristically has a sinuous basal margin and a prominent anticusp-like basal extension ( Fig. 19 View Figure 19 ; also see Zhang, 1998c, pl. 14, figs 13–17; Mellgren & Eriksson, 2006, fig. 13A–D, F–K). P. graeai differs from P. cooperi in having a straight basal margin and in lacking the anticusp-like anterobasal corner; it is distinguished from the bicostate elements of P. calceatus in having a less expanded base.

The long-based element assigned to the Sb1 and Sb2 position by Mellgren & Eriksson (2006) is only rarely represented in our collection from the Dawangou section ( Fig. 21I View Figure 21 ).

Löfgren (1978) originally defined P. parvibasis as having a trimembrate apparatus including symmetrical and asymmetrical bicostate elements, and an acostate scandodiform element. The holotype of this species is a scandodiform element ( Löfgren, 1978, pl. 3, fig. 18) bearing a suberect cusp with a faintly developed groove near the inner lateral margin on the posterior face and a short base with straight basal margin. It is morphologically closely related to M elements of the associated species P. cooperi and P. calceatus . Löfgren (1978, p. 93) suggested that the asymmetrical bicostate element of P. parvibasis was difficult to distinguish from the corresponding elements of other Protopanderodus species , and could only be differentiated by its shallower basal cavity, and differed from the corresponding element of P. graeai by having “the apex of the basal cavity placed more centrally”. These minor differences between P. graeai and P. parvibasis may be recognizable in the well-preserved Swedish material, but are of little use when dealing with less well preserved specimens with a higher CAI.

Detailed comparison between P. parvibasis and P. graeai using the recently revised and illustrated Swedish material (Mellgren & Eriksson, 2006) and our collections indicates that most likely these represent only one species. Elements referable to both species are well represented among our material from Tarim, but we had extreme difficulty in distinguishing one from the other. Close examination of the P. parvibasis specimens illustrated by Mellgren & Eriksson (2006, fig. 11A, 11H) suggests that their Sb1 and Sb2 elements should be reassigned to P. cooperi , and all the other figured specimens except the M element (Mellgren & Eriksson, 2006, fig. 11D, 11I) are identical with those illustrated by them as P. graeai . However, if we consider the M element of P. graeai defined by Mellgren & Eriksson (2006) to represent the Sc position of this species, and the M element of P. parvibasis as defined by Mellgren & Eriksson (2006) to represent the M position in the P. graeai apparatus, and further combining the Sb1, Sb2 and Sc elements of Mellgren & Eriksson (2006) as the Sb element of P. graeai , then P. parvibasis becomes a junior synonym of P. graeai . These two species also have similar stratigraphical ranges (Mellgren & Eriksson, 2006, fig. 10).

Kingdom	Animalia
Phylum	Chordata
Class	Conodonta
Order	Conodontophorida
Family	Protopanderodontidae
Genus	Protopanderodus