Psigraptus jacksoni Rickards & Stait — systematics, reconstruction, distribution and preservation

Abstract

Species of Muenzhigraptus, Diphygraptus, Hunjiangoraptus (sic), Holopsigraptus and Neoclonograptus from China are placed in synonymy with Psigraptus jacksoni Rickards & Stait. Extensive collections of P. jacksoni from the Florentine Valley Formation show the fully grown colony to have been a reclined, ‘shrubby’ cone with at least thirty terminal stipes. The species is indicative of mid-Tremadoc rocks. The preservation suggests that the stolons may have been only partially sclerotised. Three forms of preservation are present within the one bed, only one form of which shows the zooids and stolons and then very rarely. Local variations in microenvironments on and beneath the sea floor are postulated as the cause of variation in form of preservation.

Keywords:

• Psigraptus
• Tremadoc
• Tasmania
• zooids
• preservation
• taphonomy
• reconstruction