Gladigondolella laii Chen et al.

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 : 18-19

Gladigondolella laii Chen et al. morphotype A

Fig. 13B, C, G ?

2013 Neogondolella sp. ; Yan et al., fig. 6, nr. X.

2015 Neogondolella ? n. sp. A; Chen et al., figs. 9.5– 9.8. 2019 Neogondolella ? n. sp. A; Chen et al., figs. 6.8, 6.9. 2021 Gladigondolella laii sp. nov.; Chen et al., figs. 4.20, 4.21 (only).

Material. ca. 15 specimens.

Diagnosis. Segminiplanate P 1 element. Platform is arched, thickened and the platform margins are oriented orally. Denticles slightly fused at mid-length, larger and more discrete towards the anterior end.

Description. Te element is arched in lateral view. In oral view, the margins of the thickened platform are subparallel at mid-length, and taper anteriorly. Te platform is V-shaped, and the margin is directed orally. Te cusp may be conspicuous in well preserved specimens. A posterior process may be present, which bears additional posterior denticles, otherwise the posterior margin is rounded. Te carina denticles are partly fused at mid-length, taller and more discrete towards the anterior end.

Remarks. Gladigondolella laii differs from Borinella by having a more fused carina and an arched and thick platform whose margin are oriented orally. In comparison with the type species of Gladigondolella , a Middle Triassic species, the posterior process is much less developed and less arcuated in the carinal axis. Chen et al. (2015) rejected the assignment of their Ng. n. sp. A to Gladigondolella on the basis that posterior denticles are never present behind the cusp. In our material (e.g. Fig. 13C ) small denticles are present occasionally. With the exception of these additional posterior denticles, our specimens resemble those of Chen et al. (2015) very closely, hence they are synonymized here. Implicitly we assume there is variation within the species, a small posterior process being present or not. Tis taxon is thought to be intermediary between Borinella and Gladigondolella , but through the shared derived characteristic of the posterior cusp we determine it as the former genus. Chen et al., (2019; figs. 6.8, 6.9) illustrated similar and coeval (associated with Ic. collinsoni ) elements from Oman, which they assigned to Neogondolella n. sp. A. Teir illustrated specimens more closely resemble Gladigondolella tethydis (Huckriede) and were later assigned to a new species of Gladigondolella : Gladigondolella laii ( Chen et al., 2021) . To date Gladigondolella is mostly known from the Middle Triassic (e.g. Goudemand et al., 2012a; Orchard et al., 2007a, 2007b). If, as it seems, the here illustrated specimens and/or those from Chen et al., (2019, 2021) do indeed belong to Gladigondolella , then they represent their oldest known representatives of this genus so far. A few unpublished specimens from middle Smithian rocks of Oman may also belong to this genus (Leu et al., submitted; L. Dudit, pers. comm.), which further question the origin and age of Gladigondolella . Its preference for deeper, colder habitats ( Trotter et al., 2015) may then explain its spotty occurrences within the Early Triassic, preferably during relatively colder intervals and/or in deeper, colder refuge areas like Oman.

Occurrence. South China; Ic. collinsoni and Tr. homeri zone, Jiarong ( Chen et al., 2015). Bed 54, Luolou formation, Ic. collinsoni and Tr. homeri zone, Bianyang section, Guizhou ( Yan et al., 2013).

Figures

Fig. 13 (See legend on previous page.)