Hadrodontina aequabilis Staesche 1964
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
Ellisoniidae
Hadrodontina
Hadrodontina aequabilis

description: Hadrodontina aequabilis Staesche, 1964
P 1 elements: Figs. 27F–M; 28A, C, E
P 2 elements: Figs. 27B–E; 28B, D
S 2 elements: Fig. 27A
P 1 element:
*1964 Hadrodontina aequabilis n. sp.; Staesche, p. 275, figs. 43, 44.
1984 Sweetocristatus unicus n. sp.; Dagis, pp. 37–38, pl. X, figs. 6–9.
1990 Pachycladina peculiaris n. sp.; Shunxin (Zhang), pl. 2, fig. 4
1991 Pachycladina peculiaris n. sp.; Zhang in Zhang & Yang, p. 40, pl. 3, figs. 1, 2.
1997 Parapachycladina peculiaris Zhang; Shunxin et al., pp. 65–69, pl. 1, figs. 1–2, pl. 2, figs. 1–2, pl. 3 figs. 1–2.
2004 Ellisonia sp. aff. E. triassica Müller, 1956; Koike et al., figs. 8.7, 8.8.
2009 Ellisonia? cf. peculiaris Sweet; Igo in Shigeta et al., p. 182, fig. 152.22.
2013 Parachirognathus geiseri Clark; Yan et al., p. 516, fig. 6 FF.
2015 Parachirognathus peculiaris Zhang & Guo; Chen et al., figs. 8.20–21, 24.
2015 Sweetocristatus unicus Dagis; Chen et al., fig. 8.23. 2016 Hadrodontina aequabilis Staesche; Koike, pp. 164–167, fig. 2, nr. 1–3.
2018 Hadrodontina aequabilis Staesche; Maekawa in Maekawa et al., p. 18, figs. 13.3?–13.4 (only).
2020 Hadrodontina aequabilis Staesche; Sun et al., figs. 1–7 (natural assemblage of the Hadrodontina apparatus).
P 2 element:
*1964 Hadrodontina aequabilis n. sp.; Staesche, p. 275, fig. 44.
2004 Ellisonia sp. aff. E. triassica Müller; Koike et al., p. 247, fig. 8.6
2016 Hadrodontina aequabilis Staesche; Koike, p. 165, figs. 2.4 (P2 element).
2020 Hadrodontina aequabilis Staesche; Sun et al., figs. 1–7 (natural assemblage of the Hadrodontina apparatus).
S 2 element. 2004 Ellisonia sp. aff. E. triassica Müller; Koike et al., p. 247, fig. 8.4
2016 Hadrodontina aequabilis Staesche; Koike, p. 165, figs. 2.9–11.
2020 Hadrodontina aequabilis Staesche; Sun et al., figs. 1–7 (natural assemblage of the Hadrodontina apparatus).
Material. P 1, more than 40; P 2, more than 40; S 2 more than 10.
Revised diagnosis. Robust to slender angulate P 1 element. Te 6–8 (usually 7) denticles are rather short, radiating, conical, with subtriangular free ends and they are increasingly reclined towards the posterior. Te concave lower side is occupied by a large and wide groove.
Remarks. Te observed variation in the denticulation of the P 1 and P 2 elements suggests there may be scope for further specific differentiation: in some elements the height of the denticles changes smoothly along the unit (Fig. 28B), whereas in others the denticles are alternatively high and low (Fig. 28D). Dagis (1984) assigned some specimens (here considered as junior synonyms of Ha. aequabilis) to Sweetocristatus unicus. Yet, the genus Sweetocristatus Szaniawski (in Szaniawski & Malkowski, 1979) was established for Upper Artinskian to Lower Guadalupian (Permian) P 1 elements that, although superficially similar to homologous elements of Hadrodontina and Pachycladina, bear a more developed, higher cusp, a higher carina and have a more elongated process. Te cusp in Ellisonia P 1 elements is more conspicuous than in those of Hadrodontina or Pachycladina. Chen et al. (2015) illustrated coeval specimens from Jiarong they assigned to either Sweetocristatus unicus or Parachirognathus peculiaris (see their figs. 8.20 and 8.23) but we fail to distinguish them from Hadrodontina aequabilis. With three natural assemblages of Hadrodontina aequabilis from the late Smithian Helongshan Formation, South China, Sun et al. (2020) observations fits with our findings; the angulate shape and no distinct cusp in the P 1 element and the distally twisting shape of the P 2 element.
Occurrence. Russia; Smithian Hedenstroemia and tardus zone, Siberia (Dagis 1984), Zhitkov Formation, Smithian age, Abrek Bay area, South Primorye (Shigeta, 2009). China; Beisi Formation, Taiping, Pingguo Western Guangxi Province (Shunxin et al., 1997), Luolou Formation, Smithian age, Jiarong and Bianyang, Nanpanjiang Basin, southern Guizhou Province (Chen et al., 2015; Yan et al., 2013), Late Smithian Helongshan Formation, Chaohu, Anhui Province (Sun et al., 2020). Japan: Taho Formation, Shirokawa-cho, Higashiuwa-gun, Ehime Prefecture (below Smithian–Spathian boundary) (Koike 2016; Koike et al., 2004). Europe: Campiller member, Werfen Formation, Skyth, South Tirol, Italy (Staesche, 1964), Slovenia (Kolar-Jurkovšek & Jurkovšek, 2019).
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 53-56, DOI: 10.1186/s13358-022-00259-x, http://zenodo.org/record/12000082