My picks from ScienceDaily

'Terror Bird' Arrived In North America Before Land Bridge, Study Finds:

A University of Florida-led study has determined that Titanis walleri, a prehistoric 7-foot-tall flightless "terror bird," arrived in North America from South America long before a land bridge connected the two continents. UF paleontologist Bruce MacFadden said his team used an established geochemical technique that analyzes rare earth elements in a new application to revise the ages of terror bird fossils in Texas and Florida, the only places in North America where the species has been found. Rare earth elements are a group of naturally occurring metallic elements that share similar chemical and physical properties.

[more under the fold...]

The Floral Network: What Determines Who Pollinates Whom?:

A field of spring wildflowers, abuzz with busy insects seeking nectar and spreading pollen, may look like a perfect model of random interaction. But ecologists have discovered order within this anarchy. For instance, as the number of species grows, the number of interactions does too, while the connectivity (the fraction of possible interactions that actually occur) and the nestedness (the relative importance of generalist species as mutualistic partners of specialist species) shrinks. Study of such networks of species is still in its youth, and the rules that generate these patterns of interaction are still being worked out. In a new study, Luis SantamarÃa and Miguel RodrÃguez-Gironés propose that two key mechanisms, trait complementarity and barriers to exploitation, go a long way in explaining the structure of actual networks of plants and their many pollinators.

The two mechanisms each arise from fundamental aspects of the interaction between species. An insect will be unable to reach nectar in floral tubes longer than its proboscis; the tube length sets up a barrier to some species, but not to others. Each plant species also has a given flowering period. The specific activity period of each insect species will complement the flowering of some plant species more than others. Other barriers and other complementary traits have been described for a variety of plant--pollinator pairs. To explore the significance of these mechanisms, the authors modeled plant--pollinator interaction networks using a few simple rules, and compared their results to data from real networks in real plant communities. The models incorporated from one to four barrier or complementary traits, or a combination of two of each. They also tested two variations of a "neutral" interaction model, in which species interact randomly, based simply on their relative abundance.

Who Laid The First Egg? Scientists Closer To Linking Embryos Of Earth's First Animals And Their Adult Form:

A decade ago, Shuhai Xiao, associate professor of geosciences at Virginia Tech, and his colleagues discovered thousands of 600-million-year-old embryo microfossils in the Doushantuo Formation, a fossil site near Weng'an, South China. In 2000, Xiao's team reported the discovery of a tubular coral-like animal that might be a candidate for parenthood. In the February issue of Geology, the journal of the Geological Society of America, Xiao will report discoveries about the intermediary stage that links the embryo to the adult. (Cover story "Rare helical spheroidal fossils from the Doushantuo Lagerstatte: Ediacaran animal embryos come of age?" by Xiao, James W. Hagadorn of Amherst, and Chuanming Zhou and Xunlai Yuan of Nanjing Institute of Geology and Paleontology.)

Paleontologists Discover Most Primitive Primate Skeleton:

The origins and earliest branches of primate evolution are clearer and more ancient by 10 million years than previous studies estimated, according to a study featured on the cover of the Jan. 23 print edition of the Proceedings of the National Academy of Sciences. The paper by researchers at Yale, the University of Winnipeg, Stony Brook University, and led by University of Florida paleontologist Jonathan Bloch reconstructs the base of the primate family tree by comparing skeletal and fossil specimens representing more than 85 modern and extinct species. The team also discovered two 56-million-year-old fossils, including the most primitive primate skeleton ever described.