The Revision Of Tuzoia And Longquania From Early Cambrian Guanshan Biota Of Eastern Yunnan,China

Tuzoia is a kind of large bivalved arthropods which widely spreads in the Cambrian seas all over the world. Two kinds of Tuzoia (the reticulated and the dotted with nodes) from the Early Cambrian Guanshan Biota (Cambrian Stage4, Series2) are carefully and systematically studied in this thesis, including a new reticulated species in Tuzoia multispinosa sp. nov. described and the Tuzoia tylodesa Luo et Hu,2006restudied and redescribed. Besides, the ontogeny of the latter is also studied in this thesis.For a long time, paleontologists have been believing that there is only one kind of reticulated Tuzoia in the Guanshan Biota which is named as Tuzoia sinensis Pan,1957. Some reported new species were regarded as the synonyms of the Tuzoia sinensis because of the poor preservation and the obscure detailed structures. In three years the writer of this thesis gathered many Tuzoia specimens and identified a kind of new reticulated Tuzoia. This one is obviously different from the other reticulated ones in profile, spine’s number and arrangement.Tuzoia tylodesa was discovered in2006. But the rare specimens constrained its further studies and actual description. The writer gathered enough specimens which enable to designate a Plesiotype and make a comparatively perfect description of this Tuzoia.One of Tuzoia tylodesa specimens preserves some soft parts, including the visual organs, the segments protruding from the valve and the possible exopods. This is the first time for the soft parts to be discovered (excludes visual organs) since Tuzoia was first reported one hundred years ago (Walcott,1912). But because of the poor preservation, the writer just simply described its profile and structures.The writer also made the ontogeny of Tuzoia tylodesa based on the different profile of valve, spines and valve ornament. The ontogeny was divided into three stages: juvenile (the valve length is less than2cm), adolescence (the valve length is between2cm and5cm) and adult (the valve length is more than5cm).Longquania is a kind of arthropods belonging to Aglaspidia and very rare in the Guanshan Biota. This paper depicts the arthropod again based on several perfect specimens.