Discretella Orchard 2005
Creators: name: Leu, Marc
name: Bucher, Hugo
name: Vennemann, Torsten
name: Bagherpour, Borhan
name: Ji, Cheng
name: Brosse, Morgane
name: Goudemand, Nicolas
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Ozarkodinida
Gondolellidae
Discretella

description: Discretella? n. sp. B
Figs. 15N; 16B
Number of specimens:>10
Diagnosis. Segminate P 1 element with subsymmetrical, posteriorly rounded and anteriorly tapered basal cavity. Large terminal, subtriangular, recurved cusp. Anterior process bearing a few denticles only.
Description. Te element shows a large cusp at the posterior end. In lateral view, the large, recurved, subtriangular cusp is about as high as the whole unit is long. An anterior process with two or three small upright to reclined denticles is present. Te lower margin is straight to concave. In aboral view, the subsymmetrical basal cavity is sub-rounded at the posterior margin and tapers towards the anterior end.
Remarks. Tese P 1 elements most closely resemble Discretella aff. discreta, but differ in having a much shorter anterior process and recurved denticles. Tey also bear some superficial resemblance with the P 1 elements of the Spathian–Anisian genus Cornudina, but differ in their conformation of the basal cavity. Urdyella unicorna n. gen. n. sp. usually has a much thinner and larger, sickleshaped cusp and a rounded basal cavity.
Because of the absence of a posterior process, some elements, especially arched ones, resemble homologous elements of Guangxidella and could possibly be assigned to that genus, but their basal cavity do not match those of Guangxidella and resemble instead that of Discretella aff. discreta, hence we tentatively retain them within Discretella.
Occurrence. South China: Luolou, Smithian age, Laren, Guangxi.
Discretella? n. sp. C
Figs. 15O; 16A, F, M.
1989 Cratognathodus sp. A; Tang, p. 405, pl. 32, fig. 8.
2013 Neospathodus? peculiaris Sweet; Yan et al., p. 516, fig. 6M.
2014 Discretella sp. indet. A; Maekawa & Igo in Shigeta et al., p. 202–207, fig. 151.1–151.12, 151.16–151.18 (only).
2014 Genus gen. indet. D; Maekawa & Igo in Shigeta et al., p. 269, figs. 193.10–193.12.
Number of specimens:>10
Diagnosis and description. Same as Discretella? n. sp. B except that a very small posterior process without denticle is always present and the laterally twisted basal cavity tapers at both ends. Te anterior process may bear up to 5 denticles.
Remarks. Te P 1 elements of this species are very similar to those of the coeval Discretella? n. sp. B and both species may be conspecific although the presence of the incipient posterior process and the geometry of the basal cavity suggest they correspond at least to two different morphotypes, possibly due to sexual dimorphism. Tey also share strong similarities with the P 1 of Discretella? n. sp. D, which may be a descendant of Discretella? n. sp. B via reduction/loss of the anterior process, forms like, Fig. 16M (and figs. 193.10–193.12 of Maekawa and Igo in Shigeta et al., 2014) that bear only one or two anterior denticles being intermediary. Te relationship with Discretella sp. indet. A Maekawa & Igo is unclear but the P 1 of the latter is almost identical, except that the incipient posterior process bears a small triangular denticle. Maekawa & Igo noted also that the anterior process of the P 1 element of Discretella sp. indet. A (Maekawa & Igo) may also have been reduced over time. Conversely, Discretella robustus (Wang & Wang, 1976), which share a similar recurved cusp and a sigmoidal profile in lower view, has more developed anterior and posterior processes and may be their forerunner.
Occurrence. South China: Luolou, Smithian age, Laren, Guangxi.
Discretella? n. sp. D
Fig. 26 AB, AC.
2014 Genus gen. indet. D; Maekawa & Igo in Shigeta et al., p. 269, figs. 193.8–9.
Holotype. Specimen illustrated in Fig. 26 AB.
Number of specimens:>20
Diagnosis. Same P 1 element as in Discretella? n. sp. C except it bears no anterior process.
Remarks. As for Discretella? n. sp. B and C (see above) the generic assignment of these forms is uncertain and may deserve a new genus name, especially given that the present taxa bear neither posterior nor anterior denticles.
Occurrence. Laren road cut, Luolou Formation, Smithian age, Nanpanjiang basin, South China (this paper); North-eastern Vietnam, Novispathodu s ex gr. waageni Zone between Flemingites rursiradiatus beds and Urdyceras tulongensis beds and within the Owenites koeneni beds, Bac Tuy Formation (Shigeta et al., 2014).
description: Published as part of 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, pp. 1-61 in Swiss Journal of Palaeontology (19) (19) 141 (1) on pages 46-47, DOI: 10.1186/s13358-022-00259-x, http://zenodo.org/record/12000082