Tag Archives: Mass extinctions

Multis made it through, but most of the squamates scurried and slithered off…

New study looking at squamate (lizard and snake) extinction patterns across the K-Pg boundary. (It’s a really neat study, but they should have put ‘dinosaur’ in the title and it would have been a guaranteed Nature/Science hit!):

Longrich, N. R., Bhullar, B. A. S., & Gauthier, J. A. (2012). Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences, 109(52), 21396-21401.

The Cretaceous–Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification.


News Flash

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.”

Have fun!


Has the Earth’s sixth mass extinction already arrived?

Has the Earth’s sixth mass extinction already arrived?

Anthony D. Barnosky, Nicholas Matzke, Susumu Tomiya, Guinevere O. U.Wogan, Brian Swartz, Tiago B. Quental,
Charles Marshall, Jenny L. McGuire, Emily L. Lindsey, Kaitlin C. Maguire, Ben Mersey & Elizabeth A. Ferrer

Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.