Origin and Lifestyles of early Brachiopods and other Lophotrochozoans Insights from the Chengjiang and Guanshan Fossil-Lagerstätten

Sammanfattning: One of the great unsolved evolutionary questions concerns the origin and phylogeny of the major animal phyla that appeared in the fossil record more than 540 million years ago, during the Cambrian explosion. Although new molecular information has been very useful, we still have little understanding about the origin of most of the phyla of bilaterians living today. The richly diverse fossil remains from this critical early Cambrian interval are particularly well exposed in China, where exceptionally-preserved fossil lophotrochozoans including brachiopods are particularly abundant. In particular the exceptionally-preserved Cambrian lophophorates from the Chengjiang and Guanshan Lagerstätten have offered new sources of critical palaeobiological data that have been shown to be important for understanding the early ecology and evolution of lophotrochozoans. This thesis comprises a detailed study of new, abundant, exceptionally-preserved material of five lophotrochozoan species from the Chengjiang and Guanshan Lagerstätten. Kuangshanotreta malungensis from Chengjiang is the earliest known example of an attached acrotretoid brachiopod representing the oldest evidence about the palaeoecology of the diverse yet, enigmatic acrotretoid linguliform stock that comprises an important component of the Cambrian evolutionary fauna. Eoglossa chengjiangensis from Chengjiang is the earliest known representative of the Glossellinae. Diandongia pista occurs abundantly both in the Chengjiang fauna and the younger Guanshan fauna, and it’s exceptionally well-preserved and strongly mineralized shells shows that it belongs within the Botsfordiidae. In contrast, the last two species from Chengjiang examined for this thesis - Yuganotheca elegans and Cotyledion tylodes belong within the stem of the Brachiopoda and the Lophotrochozoan entoprocts.