Paper No. 225-10
Presentation Time: 9:00 AM-6:30 PM
THE FIRST OBSERVATION OF COMPLETE MACROCYSTELLA FROM THE UPPER CAMBRIAN (FURONGIAN, SANDU FORMATION) OF GUANGXI PROVINCE, SOUTH CHINA
Usually Macrocystella is regarded as a rare glyptocystitid rhombiferan (Paul, 1968, Zamora, 2009). Sprinkle (1973) rejected Macrocystella as a rhombiferan and returned it to the eocrinoids.Macrocystella is known from the late Cambrian (Furongian) to the late Ordovician (Sandbian) (Mergl and Prokop, 2006) and has been reported from the United Kingdom (Paul, 1968, 1984),France (Ubaghs 1983, 1999, Vizcaïno and Lefebvre, 1999), Germany (Sdzuy, 1955, Sdzuy et al.2001), the Czech Republic (Prokop and Petr, 1999), Argentina (Aceñolaza, 1999), Mexico (Robison and Pantoja-Alor, 1968), Spain (Gilcid et al., 1996), Morocco (Chauvel, 1969),Mongolia (Rozhnov et al., 2009), Australia (Jell et al., 1985), Korea (Kobayashi, 1935; Lee et al.,2005) and South China (Zamora et al., 2013). Although the debate about taxonomic position is still ongoing, we prefer to follow the conventional practice of Paul until the taxonomic position is fully documented. Herein, two new species of Macrocystella, M. tiani nov. sp. and M. ridgis nov. sp., are described from the upper Cambrian Sandu Formation (Furongian) in Guangxi, south China. The new species are characterized by 4 basals, 5 infra-laterals, 5 laterals, possibly 6 radials and six oral plates; a large periproct surrounded by thecal plates(L1,L4,L5,IL4 and IL5), a possible gonopose surrounded by 05 and R1, biserial unbranched brachioles grouped into 5 ambulacra and arising from the margins of theflattened oral surface. No pectinirhombs are present. The discovery of Macrocystella in southern China provides new information of the palaeobiogeographic distribution of this group, suggesting a possible connection between Laurentia and Gondwana during the late Cambrian.