Triassospathodus aff. symmetricus ( 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 : 41

Triassospathodus aff. symmetricus ( Orchard, 1995)

Figs. 18G ; 24B, E, F

2004 Neospathodus sp. aff. N. symmetricus Orchard ; Koike, p. 133, figs. 2.4–2.5.

2015 Triassospathodus symmetricus (Orchard) ; Chen et al., fig. 8.1.

Number of specimens.> 20.

Remarks. Te biostratigraphical range of these specimens is usually slightly older than that of Tr. symmetricus . Te P 1 element of Tr. aff. symmetricus resembles that of Tr. symmetricus , but is shorter with fewer denticles and a more circular and larger outline of the basal cavity. Te denticles are less inclined posteriorly compared to Tr. symmetricus and often have one additional small posteriormost denticle. Its denticles are not posteriorly arched as in Nv. pingdingshanensis . It differs from the very similar Nv. abruptus by having a downturned posterior part and posteriorly reclined denticles. Tis species might represent a transitional form between Novispathodus abruptus and Triassospathodus symmetricus but a multi-element apparatus reconstruction is currently lacking.

Occurrence. Taho Formation, Southwest Japan, Spathian age (Koike, 2004); South China, Luolou Formation, at the top of the black shales and the base of the nodular limestone in the earliest Spathian (this study).

Figures

Fig. 18 (See legend on previous page.)

Fig.24 Novispathodinae and uncertain from Qiakong,Laren,Shanggang,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, G, H Triassospathodushomeri (Bender);A LIL515C,PIMUZ 39313;D QIA155,PIMUZ 39314;G LIL513B,PIMUZ 39315;H LIL515B,PIMUZ 39316.B, E, F Triassospathodus aff.symmetricus (Orchard);B QIA138,PIMUZ 39306;E LIL505,PIMUZ 39307; F QIA136,PIMUZ 39308.C, I–Q Triassospathodussymmetricus (Orchard);C QIA140,PIMUZ 39326;I SHA313,PIMUZ 39327;J QIA143,PIMUZ 39328;K QIA144, PIMUZ 39329;L QIA141,PIMUZ 39330;M LIL515D,PIMUZ 39331;N LIL509,PIMUZ 39332;O LIL513B,PIMUZ 39333;P LIL513B,PIMUZ 39334;Q LIL513A, PIMUZ 39335.R–T Aduncodina unicosta (Ding);R BAN5,PIMUZ 39100;S SHA320,PIMUZ 39101;T SHA318,PIMUZ 39102