The aftermath of the great end-Permian period mass extinction 252 Myr ago shows how life can recover from the loss of >90% species globally. The crisis was triggered by a number of physical environmental shocks (global warming, acid rain, ocean acidification and ocean anoxia), and some of these were repeated over the next 5-6 Myr. Ammonoids and some other groups diversified rapidly, within 1-3 Myr, but extinctions continued through the Early Triassic period. Triassic ecosystems were rebuilt stepwise from low to high trophic levels through the Early to Middle Triassic, and a stable, complex ecosystem did not re-emerge until the beginning of the Middle Triassic, 8-9 Myr after the crisis. A positive aspect of the recovery was the emergence of entirely new groups, such as marine reptiles and decapod crustaceans, as well as new tetrapods on land, including — eventually — dinosaurs. The stepwise recovery of life in the Triassic could have been delayed either by biotic drivers (complex multispecies interactions) or physical perturbations, or a combination of both. This is an example of the wider debate about the relative roles of intrinsic and extrinsic drivers of large-scale evolution. from a much more devastated planet and biota than the others. With only some 10% of species surviving, the EPME was much harsher than the other mass extinctions, during which global species diversity reduced to only about 50% of the pre-extinction total 1,2,24-26 . This means that the Triassic recovery has two profound implications: first, it may show qualitative, as well as quantitative, differences from the other post-extinction recoveries; and, second, it can act as an exemplar of what to expect, at its most extreme, when global biodiversity is pushed to the brink. There are obvious implications for current concerns about biodiversity loss and recovery resulting from human impacts 27,28 . In the past ten years, attention has focused on the sedimentary successions in south China. These are enormously laterally extensive, with some formations extending more than 2,000 km from the Zhejiang to Yunnan provinces. The huge exposures, length of the sections and improving dating open up the opportunity to explore physical environmental and biotic changes through the extinction and recovery times in varied marine habitats, and compare these with patterns elsewhere in the world (Fig. 1). A fine- scale, forensic analysis of this extraordinary time in Earth's history now becomes possible. The end-Permian mass extinction The EPME killed 80-96% of marine animal species and 70% of terrestrial vertebrate species

The timing and pattern of biotic recovery following the end-Permian mass extinction

Paleophysiology and End-Permian Mass Extinction

Hearing relies on faithful synaptic transmission at the ribbon synapse of cochlear inner hair cells (IHCs). At present, the function of presynaptic ribbons at these synapses is still largely unknown. Here we show that anchoring of IHC ribbons is impaired in mouse mutants for the presynaptic scaffolding protein Bassoon. The lack of active-zone-anchored synaptic ribbons reduced the presynaptic readily releasable vesicle pool, and impaired synchronous auditory signalling as revealed by recordings of exocytic IHC capacitance changes and sound-evoked activation of spiral ganglion neurons. Both exocytosis of the hair cell releasable vesicle pool and the number of synchronously activated spiral ganglion neurons co-varied with the number of anchored ribbons during development. Interestingly, ribbon-deficient IHCs were still capable of sustained exocytosis with normal Ca2+-dependence. Endocytic membrane retrieval was intact, but an accumulation of tubular and cisternal membrane profiles was observed in ribbon-deficient IHCs. We conclude that ribbon-dependent synchronous release of multiple vesicles at the hair cell afferent synapse is essential for normal hearing.

/pdf/hair-cell-synaptic-ribbons-are-essential-for-synchronous-6aatb0prim.pdf

Hair cell synaptic ribbons are essential for synchronous auditory signalling

https://estudogeral.sib.uc.pt/bitstream/10316/3934/4/Hesselbo%20et%20al2007.pdf

Carbon-isotope record of the Early Jurassic (Toarcian) Oceanic Anoxic Event from fossil wood and marine carbonate (Lusitanian Basin, Portugal)

High-resolution oxygen isotope records document the timing and magnitude of global warming across the Permian-Triassic (P-Tr) boundary. Oxygen isotope ratios measured on phosphate-bound oxygen in conodont apatite from the Meishan and Shangsi sections (South China) decrease by 2‰ in the latest Permian, translating into low-latitude surface water warming of 8 °C. The oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates, suggesting that the addition of isotopically light carbon to the ocean-atmosphere system by Siberian Traps volcanism and related processes resulted in higher greenhouse gas levels and global warming. The major temperature rise started immediately before the main extinction phase, with maximum and harmful temperatures documented in the latest Permian (Meishan: bed 27). The coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems. In addition, very warm climate conditions in the Early Triassic may have played a major role in the delayed recovery in the aftermath of the Permian-Triassic crisis.

Climate warming in the latest Permian and the Permian-Triassic mass extinction

The continuity through the past 300 million years of key tropical sediment types, namely coals, evaporites, reefs and carbonates, is examined Physical controls for their geographical distributions are related to the Hadley cell circulation, and its effects on rainfall and ocean circulation Climate modelling studies are reviewed in this context, as are biogeographical studies of key fossil groups Low-latitude peats and coals represent everwet climates related to the Intertropical Convergence Zone near the Equator, as well as coastal diurnal rainfall systems elsewhere in the tropics and subtropics The incidence of tropical coals and rainforests through time is variable, being least common during the interval of Pangean monsoonal climates Evaporites represent the descending limbs of the Hadley cells and are centred at 10° to 40° north and south in latitudes that today show an excess of evaporation over precipitation These deposits coincide with the deserts as well as seasonally rainy climates, and their latitudinal ranges seem to have been relatively constant through time Reefs also can be related to the Hadley circulation They thrive within the regions of clear water associated with broad areas of downwelling which are displaced toward the western portions of tropical oceans These dynamic features are ultimately driven by the subtropical high-pressure cells which are the surface signature of the subsiding branches of the Hadley circulation Carbonates occupy the same areas, but extend into higher latitudes in regions where terrestrial surface gradients are low and clastic runoff from the land is minimal We argue that the palaeo-latitudinal record of all these climate-sensitive sediment types is broadly similar to their environments and latitudes of formation today, implying that dynamic effects of atmospheric and oceanic circulation control their distribution, rather than temperature gradients that would expand or contract through time

/pdf/tracing-the-tropics-across-land-and-sea-permian-to-present-uhqwcx7ygm.pdf

Tracing the tropics across land and sea: Permian to present

The most recent global “icehouse‐hothouse” climate transition in earth history began during the Permian. Warmer polar conditions, relative to today, then persisted through the Mesozoic and into the Cenozoic. We focus here on two Permian stages, the Sakmarian (285–280 Ma) and the Wordian (267–264 Ma; also known as the Kazanian), integrating floral with lithological data to determine their climates globally. These stages postdate the Permo‐Carboniferous glaciation but retain a moderately steep equator‐to‐pole gradient, judging by the level of floral and faunal differentiation. Floral data provide a particularly useful means of interpreting terrestrial paleoclimates, often revealing information about climate gradations between “dry” and “wet” end‐member lithological indicators such as evaporites and coals. We applied multivariate statistical analyses to the Permian floral data to calibrate the nature of floral and geographical transitions as an aid to climate interpretation. We then classified Sakma...

https://www.jstor.org/stable/10.1086/324203

Permian Phytogeographic Patterns and Climate Data/Model Comparisons

We use a climate model to simulate two intervals of Permian climate: the Sakmarian (ca. 280 Ma), at the end of the major Permo‐Carboniferous glaciation, and the Wordian (ca. 265 Ma). We explore the climate sensitivity to various levels of atmospheric CO2 concentration and to changes in geography and topography between the two periods. The model simulates large seasonality and high aridity in the continental interiors of both hemispheres for both periods. The northern summer monsoon weakens and the southern monsoon strengthens between the Sakmarian and the Wordian, owing to changes in geography and topography. The northern middle and high latitudes cool in winter, between the Sakmarian and Wordian, associated with northward shift of the continents. This high‐latitude cooling strengthens the winter westerlies and shifts the maximum storm‐track precipitation south. In the Southern Hemisphere, the winter westerlies weaken from the Sakmarian to the Wordian. Starting the simulations with no permanent i...

https://www.jstor.org/stable/10.1086/324204

Simulations of Permian Climate and Comparisons with Climate-Sensitive Sediments

The Permian and Triassic represent a time of major global climate change from icehouse to hothouse conditions and significant (∼25°) northward motion of landmasses amalgamated in essentially one supercontinent, Pangea. The greatest of all mass extinctions occurred around the Permian-Triassic boundary (251 Ma), although there is no consensus regarding the cause(s). Recent studies have suggested a meteor impact and worldwide die-off of vegetation, on the basis of sparse local observations. However, new analyses of global Permian and Triassic plant data in a paleogeographic context show that the scale and timing of effects varied markedly between regions. The patterns are best explained by differences in geography, climate, and fossil preservation, not by catastrophic events. Caution should be exercised when extrapolating local observations to global-scale interpretations. At the other extreme, global compilations of biotic change through time can be misleading if the effects of geography, climate, and preservation bias are not considered.

Land-plant diversity and the end-Permian mass extinction

Carbon‐isotope analyses of fossil wood from the Middle Jurassic Ravenscar Group, Yorkshire, NE England, reveal a significant excursion toward light isotopic values (δ13C change of −3 to −4‰) at about the Aalenian‐Bajocian boundary (∼174 Ma). A positive carbon isotopic excursion is also shown for the middle Bajocian (∼170 Ma) but is less clearly defined. These isotopic patterns are very similar to the few published marine carbonate records available for this time, in particular one based on belemnites from the Hebrides basin, NW Scotland, and others from pelagic limestones in Italy. The similarity of the terrestrial and marine isotope curves is an indication that the observed isotopic signal is a global phenomenon. Through parts of the Ravenscar Group (the Scarborough Formation), supplementary data from bulk organic carbon and palynofacies analysis confirm that isotopic curves based on bulk analyses may be strongly influenced by the balance of terrestrial versus marine organic matter present in th...

https://www.jstor.org/stable/10.1086/373968

P. McAllister Rees

Papers

Tracing the tropics across land and sea: Permian to present

Permian Phytogeographic Patterns and Climate Data/Model Comparisons

Simulations of Permian Climate and Comparisons with Climate-Sensitive Sediments

Land-plant diversity and the end-Permian mass extinction

Carbon-cycle perturbation in the Middle Jurassic and Accompanying Changes in the Terrestrial Paleoenvironment