22 Body Size Analysis
Maximum vesicle diameters were recorded from species descriptions, when available, for all species occurrences. Figure vesicle diameters were measured from microphotographs of acritarchs. Maximum vesicle diameters were used as a proxy for acritarch body size history and figure vesicle diameters were used as a cross-check. Maximum and figure vesicle diameters were log-transformed. Mean maximum vesicle diameters and mean figure vesicle diameters were calculated for each geochronological bin. To...
34 Rhizarians
Rhizarians include three major groups, foraminifers, cercozoans, and radiolarians. The last of these is polyphyletic recent phylogenies suggest that phaeodareans, traditionally grouped with the other radiolarian classes, polycystineans and acantharians, are derived from within cercozoans Nikolaev et al., 2004 . With a few exceptions e.g., Paulinella, chlorarachniophytes , all rhizarians are obligate heterotrophs. Radiolarians are not known from Precambrian rocks. The earliest fossil evidence...
Preface
The Neoproterozoic Era 1000-542 million years ago is a geological period of dramatic climatic change and important evolutionary innovations. Repeated glaciations of unusual magnitude occurred throughout this tumultuous interval, and various eukaryotic clades independently achieved multicellularity, becoming more complex, abundant, and diverse at its termination. Animals made their first debut in the Neoproterozoic too. The intricate interaction among these geological and biological events is a...
31 Opisthokonts
There are two main opisthokont groups the animals and the fungi. The Proterozoic fossil record of animals is worthy of an extensive review in its own right I will not discuss it here except to note that the earliest well accepted evidence for animals are 580 Ma phosphatized embryos from the Doushantuo Formation, China Xiao et al., 1998b Xiao and Knoll, 2000 Condon et al., 2005 . See papers by Jensen et al. and Bottjer and Clapham, both in this volume, for further information on Proterozoic...
32 Amoebozoans
Amoebozoans comprise two major groups the slime molds and the lobose amoebae. Slime molds have a very poor fossil record there are only two occurrences of fossilized slime molds from Phanerozoic rocks, both in Baltic amber Eocene in age Dorfelt et al., 2003, and references therein . Eosaccharomyces ramosus, an unusual organic-walled fossil from 1000 Ma shales of the Lakhanda Formation, Siberia, consists of open, web-like colonies of cells, a structure reminiscent of the aggregating cells of...
2 Eukaryotic Tree
After much flux, we seem to be converging on a stable phylogeny for eukaryotic organisms Fig. 1 Baldauf, 2003 Simpson and Roger, 2002 Keeling, 2004 Nikolaev et al. 2004 Simpson and Roger, 2004 although see, e.g., Philip et al., 2005 . Most eukaryotes fall into one of six major clades 1 the opisthokonts, containing the animals and fungi and a few unicellular groups 2 the amoebozoans, containing the lobose amoebae both naked and testate and the slime molds 3 the plants, containing the red and...
The Proterozoic Fossil Record of Heterotrophic Eukaryotes
Department of Earth Science, University of California, Santa Barbara, CA 93106, USA. 2. Eukaryotic 3. Fossil Evidence for Proterozoic 4. Why are Heterotrophs Rare in Proterozoic