Date of Award

2001

Degree Type

Thesis

Degree Name

Master of Science

Department

Geology

Abstract

An assemblage if over 9000 systematically collected fossils from the Middle Cambrian Burgess Shale was analyzed in order to resolve the palaeoecology. Sediment and fossil evidence both show that the constituent fauna was largely autochthonous. The 'standing crop' of organisms preserved with each burial event was affected by variable taphonomic factors both laterally and temporally, but information loss appears to have been minimized. An autecological review of the trophic nucleus provides new insights with regard to behavior of the organisms, including life habits and feeding strategies. Unlike their modern representatives, priapulid worms (or at least Ottoia) appear to have constructed an organic-walled chamber in which to moult, and may have included pelagic organisms in their diet. Non-selective predation by medusoid jellyfish is evidenced by the presence of shelly, lightly sclerotized, and even gelatinous prey identified within their gut cavities. The largest predators, the dinocarids (e.g., Hurdia and Anomalocaris), appear to have been restricted to a diet of soft-bodied organisms. A trophic web is reconstructed for Raymond Quarry fauna that includes secondary (and probably tertiary) carnivory. Epifaunal tiering by soft-bodied organisms is shown to have achieved considerably higher (i.e., more modern) levels than previously thought. Compositional changes in the Raymond Quarry fauna over time appear to reflect a combination of increased taphonomic filtering and an environmental shift that included increasing sediment oxygenation, perhaps related to a trend of decreasing water depth.

Included in

Geology Commons

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.