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Title: Vermiform animals from the Lower Cambrian Chengjiang Lagerstätte
Authors: Ma, Xiaoya
Supervisors: Siveter, David
Award date: 3-Jul-2009
Presented at: University of Leicester
Abstract: The exceptional preservation of the Lower Cambrian Chengjiang Lagerstätte provides a unique insight into the early evolution of vermiform animals. This study presents new vermiform taxa, describes their morphological features, hypothesizes possible modes of life and discusses phylogenetic relationships among early metazoan phyla. Morphological features are re-assessed in the Cambrian lobopodian Luolishania longicruris, and Miraluolishania haikouensis is considered to be its junior synonym. Evidence indicates that L. longicruris may have had a filter feeding lifestyle. Cladistic analysis suggests that Cambrian lobopodians are paraphyletic or even polyphyletic, and that L. longicruris with well developed sensory structures (‘antennae’, eyes and setae) and tagmosis (a distinct head and two trunk sections) may be an important representative of the stem lineage leading to arthropods. A new fossil priapulid Eximipriapulus globocaudatus is reported and described on the basis of specimens that reveal exquisite morphological details. Possible internal fertilization is suggested and a putative juvenile is described. Evidence indicates that the animal was an active burrower using a double-anchor strategy. Cladistic analysis resolves E. globocaudatus as one of the most derived Cambrian stem priapulids. The eyes of Hallucigenia fortis and Cardiodictyon catenulum are reported, along with a re-description of eyes from L. longicruris. Three visual units are found within the eyes of H. fortis and L. longicruris, suggesting that they resemble arthropod lateral visual organs and appear to represent the primitive visual systems of arthropods. Three new vermiform taxa, Acanthipos torquatus, Hamuscolex bosolveri, and Palaeomyzon discus are described. Comparison with extant taxa suggests that they may be stem group representatives of three separate phyla of extant parasitic worms. The oral disc of Palaeomyzon discus indicates a parasitic lifestyle. This study extends both the biodiversity and ecological diversity of known Early Cambrian ecosystems.
Type: Thesis
Level: Doctoral
Qualification: PhD
Rights: Copyright © the author, 2009
Appears in Collections:Theses, Dept. of Geology
Leicester Theses

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