Neospathodus bevelledi, Leu & Bucher & Vennemann & Bagherpour & Ji & Brosse & Goudemand, 2022

Leu, Marc, Bucher, Hugo, Vennemann, Torsten, Bagherpour, Borhan, Ji, Cheng, Brosse, Morgane & Goudemand, Nicolas, 2022, A Unitary Association-based conodont biozonation of the Smithian-Spathian boundary (Early Triassic) and associated biotic crisis from South China, Swiss Journal of Palaeontology (19) 141 (1), pp. 1-61 : 23-25

Neospathodus bevelledi n. sp.

Figs. 15A, D , 16P–R .

1990 Neospathodus pamirensis n. sp.; Dagis, p. 79–80, pl. 4, fig. 8, pl. 6, fig. 9 (only).

2007 Neospathodus n. sp. V Orchard; Orchard, p. 96, fig. 2.

2013 Neospathodus cristagalli Huckriede ; Yan et al., p. 516, fig. 6, I–L.

2014 Neospathodus spitiensis Goel ; Maekawa & Igo in Shigeta et al., p. 233–236, figs. 167.17–167.30, 168.7– 168.9, 168.16–168.27, 168.34–168.36, 169.4–169.9, 169.21–169.32, 170.1–3.

2014 Neospathodus sp. indet A Maekawa & Igo; Shigeta et al., p. 179, fig. 170.10–170.33.

2014 Novispathodus ex gr. waageni Sweet ; Maekawa & Igo in Shigeta et al., p. 244, figs. 179.4–179.6, 179.13–179.15.

2015 Neospathodus cristagalli Huckriede ; Chen et al., p. 112, fig. 8.12–13, 8.15.

2016 Neospathodus sp. indet A; Maekawa et al. p. 200, figs. 5.2–5.7.

2018 Neospathodus cristagalli Huckriede ; Maekawa in Maekawa et al., p.22, fig. 14.24 (only).

?2019a Novispathodus pingdingshanensis Zhao & Orchard ; Wu et al. figs. 32–34.

2021 Novispathodus waageni (Sweet) ; Sun et al., fig. 5.22 (only).

Etymology: named after the Latin (and British English) word ‘bevelled’, which refers to the wedge-like cessation of the denticles of the P 1 element.

Holotype: specimen illustrated in Fig. 15A

Paratype: specimen illustrated in Fig. 15D

Type locality: Shanggang road cut, Luolou formation, Guangxi Province, China.

Type level: Luolou Formation, within the early-to-middle Smithian limestones ( Owenites beds), 2–3 m above Flemingites limestone.

Material.> 10 specimens.

Diagnosis. A species with a segminate-to-carminate P 1 element with distinctively wedge-shaped, bevelled denticle tips. Cusp is either terminal or in front of one or two posterior denticles. Te shallow basal cavity is posteriorly elongated and tapered. In lateral view the lower margin is straight or upturned anteriorly, conspicuously upturned at mid-length, in front of the cusp, and straight or upturned posteriorly. Te denticle directly in front of the cusp and above the kick in the lower margin may get broader towards its wedge-shaped tip and is usually conspicuously broader than the other denticles.

Description. Te P 1 element is segminate to carminate (the posterior process bearing one or two denticles) and has a rigid cockscomb-like form. In lateral view, the lower margin is conspicuously bent or upturned at mid-length, the anterior and posterior parts of the lower margin making an angle of 15° to 40° and being often offset. Te anterior lower margin is straight or slightly upturned, the posterior lower margin is usually more upturned. Te upper margin is arcuate, with a peak in height slightly behind mid-length. Te length-to-height ratio of the element is about 1–1.2:1. Te moderately fused and laterally flattened denticles seem to radiate from a point that is located below the element, slightly anterior of the lower margin kick. Te denticles are usually slightly recurved posteriorly. Te cusp is located directly behind the lower margin kick and is as high as, or smaller than the up to 2 posterior denticles. Te denticle directly in front of the cusp is usually conspicuously larger and broader than the other denticles. It may get broader towards its characteristically wedge-shaped tip. In lower/aboral view, the shallow basal cavity is subtriangular, being elongated and tapered posteriorly. Te posterior end of the basal cavity can be either pointy or sub-rounded (as in the holotype). A groove runs from the basal cavity pit to the anterior end.

Remarks. Orchard (2007) was the first to differentiate such forms on the basis of their wedge-shaped denticle tips (his Neospathodus n. sp. V). Te holotype of Neospathodus pamirensis Dagis (1990) appears to fall within the scope of Ns. bevelledi n. sp. but Dagis differentiated Ns. pamirensis on the basis of a “sharply angular lower margin” of the P 1 element and “cut-off ends” of the denticles (our rough translation from Russian), which based on his illustrations seem to correspond to sharply broken denticles, not to the wedge-shaped natural end that we use as a diagnostic feature of Ns. bevelledi n. sp., a feature that cannot be observed in his holotype of Ns. pamirensis . Moreover, the “sharply angular lower margin” does not differentiate his elements from those of Ns. spitiensis . Ns. bevelledi n. sp. compares most to Ns. cristagalli and Ns. spitiensis but none of the latter display the mid-length located, broad, large and bevelled denticle that is characteristic of Ns. bevelledi n. sp. Furthermore, Ns. spitiensis , as defined and illustrated by Goel (1977) has a similarly extended basal cavity and hence a similar lower margin but a much larger length-to-height ratio of about 1.8:1, its denticles being essentially smaller and more reclined posteriorly than in Ns. bevelledi n. sp. Maekawa and Igo (in Shigeta et al., 2014) assigned similar elements from Vietnam either to Ns. spitiensis or to their ‘ Ns. sp. indet. A’. Tey differentiated ‘ Ns. sp. indet. A’ on the basis that the P 1 elements are higher and display fewer denticles. In our view, most of the elements they assigned to Ns. spitiensis are already too high to belong to Ns. spitiensis and most of them display the characteristic bevelled denticles that none of the original Ns. spitiensis possessed. Hence, they probably belong to Ns. bevelledi n. sp. instead. Teir material, however, shows a possible somewhat continuous transition between Ns. spitiensis Goel and Ns. bevelledi n. sp., suggesting a close relationship between both taxa. In comparison with Ns. cristagalli , the P 1 elements of Ns. bevelledi n. sp. are shorter and higher and although some elements display a posteriormost denticle that is triangular, it is neither smaller nor separated from the other denticles as is characteristic of Ns. cristagalli .

Occurrence. China: Bianyang and Jiarong sections, Nanpanjiang basin, Guizhou province ( Chen et al., 2015; Yan et al., 2013); Japan: Taho Formation ( Maekawa et al., 2018); Vietnam: Bac Tuy Formation, Smithian Flemingites to Owenites beds ( Shigeta et al., 2014); Oman: Smithian age (Orchard, 2007).

Figures

Fig. 15 Neogondolellinae and Mullerinae from Qiakong, Laren and Shanggang. Magnification is ×80.The scale bar is 400 μm. All elements are considered to be P1 elements if not specifically identified otherwise. A, D Neospathodus bevelledi n. sp.; A SHA333,PIMUZ 39176; D, SHA332, PIMUZ 39177. B, J Discretella aff. discreta (MÜller); B SHA304, PIMUZ 39104; J SHA334,PIMUZ 39105. C, L Discretella discreta (MÜller); C SHA334, PIMUZ 39107; L SHA332, PIMUZ 39108. E Guangxidella bransoni (MÜller); SHA304, PIMUZ 39139.F, H, K, M, P Discretella pseudodieneri n. sp.; F QIA124, PIMUZ 39120; H QIA124,PIMUZ SQL54990; K QIA121, PIMUZ 39121; M QIA120, PIMUZ 39122; P LAR232, PIMUZ 39123. G Discretella cf. discreta (MÜller); QIA120, PIMUZ 39109.I sp. indet.; QIA120, PIMUZ 39294. N Discretella? n. sp. B; LAR232, PIMUZ 39112.O Discretella? n. sp. C; SHA342,PIMUZ 39114

Fig. 16 Neogondolellinae, Novispathodinae and Mullerinae from Shanggang and Youping cascade. Magnification is ×80.The scale bar is 400 μm. All elements are considered to be P1 elements if not specifically identified otherwise. A, F, M Discretella? n. sp. C; A YC16,PIMUZ 39115; F YC16, PIMUZ 39116; M SHA342C, PIMUZ 39117. B Discretella? n. sp. B;YC16, PIMUZ 39113. C Discretella aff.discreta (MÜller);YC22,PIMUZ 39106. D, S Discretella discreta (MÜller); D YC16, PIMUZ 39110; S SHA304C, PIMUZ 39111. E Novispathodus ex gr. abruptus (Orchard);YC41, PIMUZ 39225. G–I, K, L, N, O Discretella pseudodieneri n. sp.; G YC16, PIMUZ 39124; H YC25, PIMUZ 39125; I SHA304C,PIMUZ 39126; K YC22, PIMUZ 39127,L YC25, PIMUZ 39128; N SHA304C,PIMUZ 39129; O SHA343C,PIMUZ SQL54979. J Guangxidella bransoni (MÜller);YC16, PIMUZ 39140. P–R Neospathodus bevelledi n. sp.; P SHA 304C,PIMUZ 39178; Q SHA333C, PIMUZ 39179; R YC12, PIMUZ 39180