Eumetazoan Fossils in Terminal Proterozoic Phosphorites?

Phosphatic sedimentary rocks preserve a record of early animal life different from and complementary to that provided by Ediacaran fossils in terminal Proterozoic sandstones and shales. Phosphorites of the Doushantuo Formation. South China. contain eggs, egg cases, and stereoblastulae that document animals of unspecified phylogenetic position; small fossils containing putative spicules may specifically record the presence of sponges. Microfossils recently interpreted as the preserved gastrulae of cnidarian and bilaterian metazoans can alternatively be interpreted as conventional algal cysts and/or egg Eases modified by diagenetic processes known to have had a pervasive influence on Doushantuo phosphorites. Regardless of this interpretation, evidence for Doushantuo eumetazoans is provided by millimeter-scale tubes that display tabulation and apical budding characteristic of some Cnidaria, especially the extinct tabulates. Like some Ediacaran remains, these small, benthic, colonial fossils may represent stemgroup eumetazoans or stem-group cnidarians that lived in the late Proterozoic ocean.Organismic and Evolutionary Biolog

Morphological Reconstruction of Miaohephyton Bifurcatum, a Possible Brown Alga from the Neoproterozoic Doushantuo Formation, South China

On the basis of morphological and taphonomic study of a large sample population, Miaohephyton bifurcatum Steiner, emend. from the terminal Proterozoic Doushantuo Formation (600-550 Ma), South China, is interpreted as algal fragments shed from their parent thalli for reproductive or environmental reasons. Characters such as regularly dichotomous, multicellular thalli with forked tips, apical and intercalary meristematic growth, abscission structures, and possible conceptacles collectively suggest an affinity with the brown algae, in particular the order Fucales. In conjunction with reports of xanthophyte fossils in older Neoproterozoic rocks, this reinterpretation of Miaohephyton bifurcatum indicates that photosynthetic stramenopiles (chrysophytes, synurophytes, xanthophytes, phaeophytes, and diatoms; or chromophytes sensu stricto) diversified during the Neoproterozoic Era along with the red and green algae. This, in turn, suggests that the secondary endosymbiosis that gave rise to the photosynthetic stramenopiles took place relatively soon after the evolutionary transformation of cyanobacteria to rhodophyte plastids.Organismic and Evolutionary Biolog

New morphological observations for Paleoproterozoic acritarchs from the Chuanlinggou Formation, North China

Acritarchs from the Chuanlinggou Formation (ca. 1700 Ma) were first reported by Xing and Liu (1973) [Xing, Y.S., Liu, G.Z., 1973. On Sinian micro-flora in Yenliao Region of China and its geological significance. Acta Geological Sinica 1, 1-64] and some were later described as eukaryotes by Yan (1982) [Yan, Y.Z., 1982. Schizofusa from the Chuanlinggou Fromation of Changzhougou System in Jixian county. Bulletin of the Tianjin Institute of Geology and Mineral Resources 6, 1-7]. The eukaryotic affinity has been questionable, however, for lack of indisputable morphological evidence. Chuanlinggou acritarchs are some of the oldest acritarchs found on Earth and are well preserved for ultrastructure study. In this study, Chuanlinggou acritarchs were examined by jointly using optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In most cases, an ovoidal group of acritarchs represents a half vesicle following a complete longitudinal rupture, which is a morphological model different from a whole envelope with medial splits as proposed by earlier studies. This ovoidal group displays a bipolar morphology, longitudinal rupture, and occasionally striated wall structures that are consistent with a eukaryotic affinity. Thus, the Chuanlinggou ovoidal acritarchs probably extends the eukaryotes body fossil record into the Paleoproterozoic, ∼200 million years earlier than the morphologically more complex acritarchs from Mesoproterozoic Roper Group (ca. 1500 Ma). © 2008 Elsevier B.V

Amino acid residues in conodont elements

Thermally unaltered conodont elements, brachiopods. and vertebrates were analyzed with reverse phase high profile liquid chromatography to locate and quantify amino acid remnants of the original organic matrix in the fossils. No consistent similarities in amino acid content were found in conodont taxa. and criteria based on organic residues appear to have no taxonomic significance in the fossils tested from these localities. However, hydroxyproline. an amino acid that is found in the collagen molecules of animals. as well as in the glycoproteins in the cell walls and reproductive tissues of certain plants, is represented in most taxa. The organic matter retained in the impermeable crowns of conodont elements might have been derived originally from a form of collagen. Biochemical analyses. correlated with histochemical tests, demonstrate that organic matter is an integral part of the hyaline tissue of the element crown and not the result of surface contamination. Tests of a range of vertebrate and invertebrate fossil hard tissues produced similar results. The analyses indicate that hyaline tissue in the conodont element crown is not a form of vertebrate enamel. which contains no collagen. Albid tissue. with little or no organic content. is not a form of vertebrate bone or dentine, both based on collagen and low in mineral. Although these results do not help to determine the phylogenetic affinities of conodont animals, they indicate teat conodont elements do not contain hard tissues characteristic of vertebrate animals