Internal supporting structures of some Late Ordovician graptolites from South China revealed by micro‐CT
DOI | 10.1111/let.12365 |
---|---|
Aasta | 2020 |
Ajakiri | Lethaia |
Köide | 53 |
Number | 3 |
Leheküljed | 396-408 |
Tüüp | artikkel ajakirjas |
Keel | inglise |
Id | 16119 |
Abstrakt
Three‐dimensionally preserved pyritic internal moulds of the Late Ordovician graptolites Appendispinograptus leptothecalis and Styracograptus chiai from the Upper Ordovician Wufeng Formation of the Daheba section, Hunan Province, South China, were imaged by micro‐CT. The distinctive pea‐shaped pits/dimples aligned in a zigzag line arising from the second/third thecal pair on the tubarium in these species are interpreted as the surface expression of the junction between the lateral thecal walls and the thickened internal cross‐bars that support the nema. The relations between different internal structures such as the nema, median septum, aboral lists, interthecal septa and cross‐bars are summarized, and examples of these supporting systems in different taxa are illustrated. The presence of isolated cross‐bars in different diplograptid tubarium may suggest that they have evolved as a result of constructional restrictions.