Hadrodontina aequabilis Staesche, 1964

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 : 53-56

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).

Figures

Fig. 27 Hadrodontinae from Qiakong, Laren, Shanggang and Lilong. Magnification is ×80.The scale bar is 400 μm. All elements are considered to beP1 elements if not specifically identified otherwise. A, Hadrodontina aequabilis (S2 element) (Staesche);SHA344, PIMUZ 39141. B–E, Hadrodontina aequabilis (P2 element) (Staesche); B LAR214, PIMUZ 39142;C QIA13, PIMUZ 39143; D LIL500,PIMUZ 39144,E SHA344,PIMUZ 39145. F–M Hadrodontina aequabilis (Staesche); F LIL502, PIMUZ 39146; G LIL503, PIMUZ 39147; H QIA134, PIMUZ 39148; I QIA134,PIMUZ 39149; J QIA 133, PIMUZ 39150; K LIL502,PIMUZ 39151; L LIL501,PIMUZ 39152; M LIL501, PIMUZ 39153

Fig. 28 Hadrodontinae from Shanggang.Magnification is × 80.The scale bar is 400 μm. All elements are considered to be P1 elements if not specifically identified otherwise. A, C, E Hadrodontina aequabilis (Staesche); A SHA 345C, PIMUZ 39154; C SHA345C,PIMUZ 39155; E SHA344C, PIMUZ 39156. B, D Hadrodontina aequabilis (P2 element) (Staesche); B SHA345C, PIMUZ 39157; D SHA345C, PIMUZ 39158

Fig. 2 Pictures from four of the five studied sections in the Nanpanjiang basin. A Qiakong, B Shanggang, C Laren (Kuang Guodun for scale), D Lilong (Hugo Bucher for scale)

Fig. 1 A Locations of the studied sections in the Nanpanjiang Basin (Luolou platform) (modified from Bagherpour et al., 2017). a—flood alluvial facies, b—shallow water siliclastic deposit, c—carbonate platform,d—slope,e—basin. Sections: 1—Qiakong, 2—Laren, 3—Shanggang, 4—Lilong, 5—Youping cascade.B Simplified palaeogeographical map of the Early Triassic (modified after the PANALESIS plate tectonic model of Vérard, 2019) South China indicated with a star