February Geology and GSA Today media ...(Republic that contains a diverse and wel...)

Date:1/22/2008

Republic that contains a diverse and well-preserved fossil taxa by obtaining a uranium-lead (U-Pb) age on the primary aragonite of a pristine Miocene age coral. The recognition that such ancient corals may be sufficiently well preserved to allow direct U-Pb dating opens doors for continued refinement of late Cenozoic sedimentary sequences.

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Size of the earliest mollusks: Did small helcionellids grow to become large adults?
Mnica Mart Mus et al., Area de Paleontologa, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain. Pages 175-178.

The oldest widely accepted mollusks are a group of cap-shaped fossil shells known as helcionellids. Helcionellids are usually very small (1-2 millimeters), which has contributed to the belief that ancestral mollusks were millimeter-scale animals. Mollusks are usually born with a shell which accompanies them their whole life. As they grow in size, so does the shell, but only at the margins; therefore, the juvenile shell always remains visible at the tip of the adult one. Mart Mus et al. have discovered a new, large (2 centimeter) mollusk from the Cambrian in Spain which has preserved, at the tip of its large shell, a tiny cap identical to the small helcionellids previously found only as "free" elements in Cambrian rocks. Considering the mode of growth of molluskan shells, Mart Mus et al.'s finding shows that at least some small helcionellids represent juvenile (or maybe even larval) stages of species that reached a centimeter-scale adult size. Therefore, contrary to a widely held wisdom, ancestral mollusks may have been relatively large animals.

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Extinction and environmental change across the Eocene-Oligocene boundary in Tanzania
Paul Pearson et al., School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3YE, UK. Pages 179-182.

The transition between the Eocene and Oligocene epochs (between approximately 33.5
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Contact: Ann Cairns acairns@geosociety.org 303-357-1056 Geological Society of America Source:Eurekalert

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