New Light on Permian Extinction

Perhaps the Permian extinctionapplied mostly to the ocean by drastically altering the chemistry in the lifezone.  That could be expected withvolcanism running amok.  That does open thedoor for land based refugia quite able to support populations not directly downwind from that volcanism.

Thus the severe destruction ofthe global marine population reflects the natural dispersal of toxicity in theOceans (95% reported) and the much more reasonable 70% for land based creatureswhich may have had even lower real losses.

Here we learn that the so calledparareptiles were barely affected and that the damage on land was much betterhandled than thought.  It makes sense ofcourse.  Land does not allow actualmixing and dispersion of volcanic toxins, at least to the point that most creaturescan get out of the way.

Statistical tools are nicelycleaning up a lot of long unquestioned assumptions about the fossil record andthis is a good example.

Reptile 'cousins' shed new light on end-Permian extinction

by Staff Writers

Bristol, UK (SPX) May 09, 2011

http://www.terradaily.com/reports/Reptile_cousins_shed_new_light_on_end_Permian_extinction_999.html

The end-Permian extinction, by far the most dramatic biological crisis toaffect life on Earth, may not have been as catastrophic for some creatures aspreviously thought, according to a new study led by the University of Bristol.

An international team of researchers studied the parareptiles, adiverse group of bizarre-looking terrestrial vertebrates which varied in shapeand size.

Some were small, slender, agile and lizard-like creatures, while othersattained the size of rhinos; many had knobbly ornaments, fringes, and bonyspikes on their skulls.

The researchers found that, surprisingly, parareptiles were not hitmuch harder by the end-Permian extinction than at any other point in their 90million-year history.

Furthermore, the group as a whole declined and diversified time andtime again throughout its history, and it was not until about 50 million yearsafter the end-Permian crisis that the parareptiles finally disappeared.

During the end-Permian extinction, some 250 million years ago, entiregroups of animals and plants either vanished altogether or decreasedsignificantly in numbers, and the recovery of the survivors was at times slowand prolonged before new radiations took place.

By studying the fossil record,palaeontologists can examine how individual groups of organisms responded tothe end-Permian event and assess just how dramatic it was.

However, as the quality and completeness of the fossil record variesconsiderably, both geographically and stratigraphically, palaeontologists needto find a way to 'join the dots' and piece together the fragments of a complexmosaic to give a more satisfactory and better picture of ancient life'sdiversity.

The team led by Dr Marcello Ruta of Bristol'sSchool of Earth Sciences, and including scientists from Germany, Braziland North America, used the evolutionaryrelationships among known parareptiles to produce a corrected estimate ofchanging diversity through time.

Dr Marcello Ruta said: "Evolutionary relationships can besuperimposed on a time scale, allowing you to infer missing portions of pastdiversity.

"They are powerful tools that complement and refine the knownrecord of extinct diversity.If you visualize evolutionary relationships in the form of branching diagramsand then plot them on a time scale, new patterns begin to emerge, with gaps inthe fossil record suddenly filling rapidly."

One of the team members, Juan Cisneros of the Universidade Federal doPiaui, Ininga, Brazil said: "It is as ifghosts from the past appear all of a sudden and join their relatives in a bigfamily tree - you have a bigger tree. This way, you can start analysingobserved and extrapolated abundance of species through time, and you canquantify novel origination and extinctionevents that would otherwise go unnoticed if you were to look at knownfinds only."

Co-author Johannes Muller of the Museum fur Naturkunde, Berlinadded: "Researchers who investigate changing diversity through time have ahuge battery of basic and advanced analytical and statistical methods at theirdisposal to study patterns of diversification and extinction.

"Classic text-book views of waxing and waning of groups throughdeep time will certainly benefit, where possible, from the use of evolutionarythinking."

University of Washington's Linda Tsuji, also part of the researchteam, concluded: "This is the first time that the history of parareptileshas been examined in such detail. But this is only the beginning. Thesebizarre-looking vertebrates continue to inspire generations of researchers, notonly those interested in mass extinctions.

They are abundant, diverse, and we still know very little about theirbiology. We hope that this study will initiate a more in-depth study of theresponse of terrestrial vertebrates to global catastrophes."

Ruta, M., Cisneros, J.C., Liebrecht, T., Tsuji, L.A. and Muller, J. 'Amniotes through majorbiological crises: faunal turnover among parareptiles and the end-Permian massextinction' in Palaeontology