Icriospathodus aff. crassatus ( Orchard, 1995 )

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 : 43-44

Icriospathodus aff. crassatus ( Orchard, 1995)

Figs. 22A ?, D?; 25G–L, N

2019 Icriospathodus crassatus (Orchard) ; Liu et al., pl. 4, figs. 10, 14.

Number of specimens:>30

Diagnosis. In lateral view, the segminate P 1 element is subrectangular. Moderately fused carina. Denticles increasingly lower at both anterior and posterior ends. Posteriormost denticles often bent inwards. Basal cavity generally symmetrical and subquadrate to subtriangular in shape. Lateral margins and basal cup often relatively thick and sometimes accessory nodes on the latter.

Description. In oral view, the rather symmetrical large basal cavity looks bulbous. Laterally, the thick node-like, irregular denticles are lower and more bent inwards towards the posterior end. Te basal cavity is symmetrical. Te subterminal cusp is situated near the posterior end, up to two more reclined denticles being sometimes present behind it. Te lower margin is downturned posteriorly.

Remarks. Orchard (1995) created Ic. crassatus for Ic. collinsoni -like elements that lack the ridge-like or paired platform nodes. Our specimens share the attributes of Ic. crassatus but their basal cavities are subsymmetrical, which is uncommon for Ic. crassatus . Te elements of N. symmetricus have a similar outline in lateral view but have relatively higher and more uniform denticles with a pointy tip, and a relatively larger basal cavity. In our material, Ic. zaksi and Ic. aff. crassatus are morphologically similar, but Ic. aff. crassatus is longer, bears more denticles, has a relatively smaller basal cavity and is usually found in younger strata. Ic. zaksi may be a forerunner of Ic. aff. crassatus . In the material studied from South China, no “true” Ic. crassatus was found. In addition, all illustrated specimens from South China determined as Ic. crassatus from the literature can neither be determined as Ic. crassatus sensu stricto in the authors view. Te specimen illustrated in Lehrmann et al. (2015) (fig. 5.16, 5.17), resembles more Tr. homeri (see Additional files). Te studies from West and North Pingdingshan do either not provide any illustrations ( Liang et al., 2011; Zhao et al., 2007, 2008) or the specimens cannot be determined as Ic. crassatus with certitude because the specimens are broken and resembles more Ic. cf. zaksi (Pl. 6 fig. 2) or Ic. cf. aff. crassatus (Pl. 12 fig. 11) in Zhao (2005). In Ji et al. (2011) the illustrated specimen from Qingyan consists of a large subsymmetrical basal cavity and resembles more Ic. aff. crassatus . Te specimen determined as Ic. crassatus in Liu et al. (2019) is in the synonymy list of Ic. aff. crassatus (see above). Furthermore, the specimen illustrated in Yan et al. (fig. 6GG, 2013) resembles more Tr. homeri with an inturned posterior end. Terefore, it has to questioned if Ic. aff. crassatus is provincialistic of South China and is worth of defining a new species formally in the future.

Occurrence. South China, Nanpanjiang basin, Luolou Fm., Laren, Lilong, Shanggang top of black shales to nodular limestone, SSB and early Spathian, (this study).

Figures

Fig. 22 Novispathodinae from Laren and Lilong. Magnification is ×80.The scale bar is 400 μm. All elements are considered to be P1 elements if not specifically identified otherwise. A, D Icriospathodus cf. crassatus? (Orchard); A BAN1, PIMUZ 39168; D LIL513A,PIMUZ 39169.B, E Novispathodus brevissimus (Orchard); B LIL513B,PIMUZ 39194; E LIL514A,PIMUZ SQL55056. C, F Novispathodus cf, brevissimus (Orchard); C LIL513A, PIMUZ 39196; F, LIL514A, PIMUZ 39198