STUDIES ON THE SHELL ULTRASTRUCTURE AND ONTOGENY OF THE OLDEST ACROTRETID BRACHIOPODS FROM SOUTH CHINA
Article
Figures
Metrics
Preview PDF
Reference
Related
Cited by
Materials
Abstract:
Acrotretids attained great diversity and cosmopolitan distributions in rocks of midCambrian to Ordovician age,and went extinct by the end of the Devonian. However, bearing significantly special morphology and column structures,it has so far been difficult to analyze their phylogenetic relationship with other groups within the Class Lingulata.Eohadrotreta,one of the oldest known acrotretoid brachiopods,are described from the lower Cambrian Shuijingtuo Formation of South China. The ontogeny and three-layered shell structure are investigated for the first time.The detailed study of ultrastructure of shell indicates that there are four ontogenetic developmental stages of the acrotretid Eohadrotreta,including protegulum,brephic shell,neanic shell,mature shell.The plank-totrophic larva and the metamorphosis are verified at least in Cambrian acrotretids. More importantly,exquisitely preserved epithelial cell moulds are identified on the whole interior of both ventral and dorsal valves. Investigation of the new material demonstrates that the disposition of epithelial cell moulds in shell interiors most likely is associated with regions of thickened muscle attachments–a character that potentially could be of use in taxonomy.The cosmopolitan distribution of early Cambrian Eohadrotreta in southern Shaanxi,eastern Three Gorges area and central Guizhou of Yangtze Platform,possible North China,Himalaya and Australia demonstrates that can be a potential index fossil for the global stratigraphic correlation of Cambrian Series 2.
