Discretella discreta ( Müller, 1956 )

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 : 45

Discretella discreta ( Müller, 1956)

Figs. 15C, G, L ; 16D, S .

*1956 Ctenognathodus discreta n. sp.; Müller, pp. 821– 822, pl. 95, fig. 28.

1989 Neospathodus discreta (Müller) ; Tang, p. 402, pl. 30, fig. 7.

2005 Discretella sp. A ; Orchard, p. 83, fig. 8.

2008 Discretella discreta (Müller) ; Orchard 2008, p. 402, figs. 8.18, 8.19.

2010 Discretella discreta (Müller) ; Beranek et al., p. 65, figs. 6.18, 6.19.

2014 Discretella discreta (Müller) ; Maekawa & Igo in Shigeta et al., pp. 196–202, figs. 141.13–141.33, 142–145, 146.1–146.30.

2018 Discretella discreta (Müller) ; Maekawa in Maekawa et al., p. 23, fig. 14.4.

Number of specimens:>20

Diagnosis. See Müller, 1956.

Description. Te carminate-to-segminate P 1 element has an upturned and inverted basal margin in the posterior one-third to one-half of the element. Te cusp is usually larger than the other discrete and upright denticles but not conspicuously.

Remarks. Maekawa & Igo (in Shigeta et al., 2014) described two different morphotypes, A and B, for Discretella discreta . Teir morphotype A would correspond to the holotype ( Müller, 1956) and their morphotype B has an upturned posterior margin and a relatively broader and triangular cusp. Although Maekawa & Igo (in Shigeta et al., 2014) have recently illustrated numerous specimens, the intraspecific variation of this species remains unclear due to its general scarcity. Based on their illustrations and unpublished material, there seems to be scope for further differentiation. Both morphotypes A and B have a posterior process and hence a tapered posterior margin of the basal cavity. However, some of our specimens do not develop a posterior process and have a rounded posterior margin at the basal cavity. Tose are here assigned to a different species, which for now is kept in open nomenclature ( Discretella aff. discreta ).

Occurrence. Wide global occurrence in the Smithian. Meekoceras beds, Nevada ( Müller, 1956). Euflemingites romunderi Zone, Canadian Arctic ( Orchard, 2008) . Jabal Safra, Oman ( Orchard, 2005). North Vietnam (Tang, 1989). Nv. ex. gr. waageni Zone, Taho Formation , Japan ( Maekawa et al., 2018).

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 (See legend on previous page.)