This month’s Evolution & Development has several interesting articles (http://onlinelibrary.wiley.com/doi/10.1111/ede.2011.13.issue-6/issuetoc), in particular, an article on odontode evolution and another on digit development in pigs.
Teeth before jaws? Comparative analysis of the structure and development of the external and internal scales in the extinct jawless vertebrate Loganellia scotica
Martin Rücklin, Sam Giles, Philippe Janvier, Philip C. J. Donoghue
Developmental basis of mammalian digit reduction: a case study in pigs
Karen E. Sears, Allison K. Bormet, Alexander Rockwell, Lisa E. Powers, Lisa Noelle Cooper, Matthew B. Wheeler
The End-Permian Mass extinction
Shen, S.-z., Crowley, J. L., Wang, Y., Bowring, S. A., Erwin, D. H., Sadler, P. M., Cao, C.-q., Rothman, D. H., Henderson, C. M., Ramezani, J., Zhang, H., Shen, Y., Wang, X.-d., Wang, W., Mu, L., Li, W.-z., Tang, Y.-g., Liu, X.-l., Liu, L.-j., Zeng, Y., Jiang, Y.-f. & Jin, Y.-g., 2011: Calibrating the End-Permian Mass Extinction.
–ScienceExpress: [doi: 10.1126/science.1213454]
“The end-Permian mass extinction was the most severe biodiversity crisis in earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 Ma, following a decline of 2‰ in δ13C over 90,000 years, and coincided with a δ13C excursion of -5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years, and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.”