Manash (Subhaditya Edusoft): PERMIAN MASS EXTINCTION SERIES 10 : PERMIAN MASS EXTINCT OF MARINE ANIMALS

EXTINCTION OF PERMIAN MARINE ANIMALS LIKE SHARKS,TRILOBITES AND AMMONITES

Permian–Triassic extinction event:

The Permian–Triassic extinction event, colloquially known as the Great Dying,was an extinction event that occurred around the boundary between the Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras. It is Earth's most severe known extinction event, with the extinction of 57% of biological families, 62% of genera, 81% of marine species, and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects. It is the greatest of the "Big Five" mass extinctions of the Phanerozoic. There is evidence for one to three distinct pulses, or phases, of extinction, with the major pulse of marine extinction occurring in a 60,000-100,000 year interval around 251.902 million years ago (mya) marking the boundary between the Permian and Triassic periods. There is some controversy regarding the chronology of the extinctions on land and whether they are synchronous with the main marine extinction event.

The scientific consensus is that the main cause of the extinction was the flood basalt eruptions that created the Siberian Traps, which released sulfur dioxide and carbon dioxide, resulting in euxinia (oxygen-starved, sulfurous oceans),[elevated global temperatures and acidified oceans. The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to the ocean-atmosphere system during this period.

Several other contributing factors have been proposed, including the emission of carbon dioxide from the burning of oil and coal deposits ignited by the eruptions; emissions of methane from the gasification of methane clathrates ;emissions of methane by novel methanogenic microorganisms nourished by minerals dispersed in the eruptions; longer and more intense El Niño events; and an extraterrestrial impact that created the Araguainha crater and caused seismic release of methane and the destruction of the ozone layer with increased exposure to solar radiation

DUE TO THE DEPOSIT OF BURNING LAVA STONE FROM VOLCANO TO PERMIAN OCEAN CAUSES ACIDIFICATION AND DEPLETION OF OXYGEN(ANOXIA). DUE TO THIS CATASTROPHIC EVENT MORE THAN 80% MARINE ANIMALS INCLUDING AMMONITES, TRILOBITES AND SHARKS POPULATION DESTROYED.

Dating:

Previously, it was thought that rock sequences spanning the Permian–Triassic boundary were too few and too incomplete for scientists to reliably determine their details. However, it is now possible to date the extinction with millennial precision. U–Pb zircon dates from five volcanic ash beds from the Global Stratotype Section and Point for the Permian–Triassic boundary at Meishan, China, establish a high-resolution age model for the extinction – allowing exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales. The first appearance of the conodont Hindeodus parvus has been used to delineate the Permian-Triassic boundary.

The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031 million years ago, a duration of 60 ± 48 thousand years. A large, abrupt global decrease in δ13C, the ratio of the stable isotope carbon-13 to that of carbon-12, coincides with this extinction, and is sometimes used to identify the Permian–Triassic boundary and the Permian-Triassic Mass Extinction event (PTME) in rocks that are unsuitable for radiometric dating. The negative carbon isotope excursion's magnitude was 4–7% and lasted for approximately 500 kyr,though estimating its exact value is challenging due to diagenetic alteration of many sedimentary facies spanning the boundary.

Marine organisms Extinction :

Marine invertebrates suffered the greatest losses during the P–Tr extinction, although previous estimates of 90–96% marine species extinction were due to historical conflation with the end-Capitanian mass extinction, which occurred 7–10 million years earlier. Evidence of these losses was found in samples from south China sections at the P–Tr boundary. Here, 286 out of 329 marine invertebrate genera disappear within the final two sedimentary zones containing conodonts from the Permian. The decrease in diversity was probably caused by a sharp increase in extinctions, rather than a decrease in speciation.

INVERTIBRATE ARTHROPODS MARINE TRILOBITES BECAME MORE OR LESS EXTINCT DURING THIS PERIOD

The extinction primarily affected organisms with calcium carbonate skeletons, especially those that relied on stable CO2 levels to produce them. These organisms were susceptible to the effects of the ocean acidification that resulted from increased atmospheric CO2. Organisms that relied on haemocyanin or haemoglobin for transporting oxygen were more resistant to extinction than those utilizing hemerythrin or oxygen diffusion. There is also evidence that endemism was a strong risk factor influencing a taxon's likelihood of extinction. Bivalve taxa that were endemic and localized to a specific region were more likely to go extinct than cosmopolitan taxa. There was little latitudinal difference in the survival rates of taxa. Organisms that inhabited refugia less affected by global warming experienced lesser or delayed extinctions.[106]

Among benthic organisms the extinction event multiplied background extinction rates, and therefore caused maximum species loss to taxa that had a high background extinction rate (by implication, taxa with a high turnover). The extinction rate of marine organisms was catastrophic.Bioturbators were extremely severely affected, as evidenced by the loss of the sedimentary mixed layer in many marine facies during the end-Permian extinction.

Surviving marine invertebrate groups included articulate brachiopods (those with a hinge), which had undergone a slow decline in numbers since the P–Tr extinction; the Ceratitida order of ammonites; and crinoids ("sea lilies"), which very nearly became extinct but later became abundant and diverse. The groups with the highest survival rates generally had active control of circulation, elaborate gas exchange mechanisms, and light calcification; more heavily calcified organisms with simpler breathing apparatuses suffered the greatest loss of species diversity.In the case of the brachiopods, at least, surviving taxa were generally small, rare members of a formerly diverse community.

Conodonts were severely affected in both taxonomic and morphological diversity, though not as severely as during the Capitanian mass extinction.

AMMONITES

AMMONITES

The ammonoids, which had been in a long-term decline for the 30-million years since the Roadian (middle Permian), suffered a selective extinction pulse 10-million years before the main event, at the end of the Capitanian stage. In this preliminary extinction, which greatly reduced disparity, or the range of different ecological guilds, environmental factors were apparently responsible. Diversity and disparity fell further until the P–Tr boundary; the extinction here (P–Tr) was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low. The range of morphospace occupied by the ammonoids, that is, their range of possible forms, shapes or structures, became more restricted as the Permian progressed. A few million years into the Triassic, the original range of ammonoid structures was once again reoccupied, but the parameters were now shared differently among clades.

Ostracods experienced prolonged diversity perturbations during the Changhsingian before the PTME proper, when immense proportions of them abruptly vanished. At least 74% of ostracods died out during the PTME itself.

Bryozoans had been on a long-term decline throughout the Late Permian epoch before they suffered even more catastrophic losses during the PTME,being the most severely affected clade among the lophophorates.

Deep-water sponges experienced significant loss of diversity and a decrease in spicule size over the course of the PTME. Shallow-water sponges were affected much less strongly; they experienced an increase in spicule size and a much lower loss of morphological diversity compared to their deep-water counterparts.

Foraminifera experienced a severe diversity bottleneck. Evidence from South China indicates the foraminiferal extinction had two pulses. Foraminiferal biodiversity hotspots shifted into deeper waters during the PTME. Approximately 93% of latest Permian foraminifera became extinct, with 50% of the clade Textulariina, 92% of Lagenida, 96% of Fusulinida, and 100% of Miliolida disappearing. Foraminifera that were calcareous suffered an extinction rate of 91%. The reasons why lagenides survived while fusulinoidean fusulinides went completely extinct may have been the greater range of environmental tolerance and greater geographic distribution of the former compared to the latter.

The buzzsaw shark (Helicoprion) AND MANY OTHER SPECIES DESTROYED DURING PERMIAN PERIOD

The buzzsaw shark (Helicoprion) AND MANY OTHER SPECIES DESTROYED DURING PERMIAN PERIOD

Cladodontomorph sharks were able to survive (albeit barely) the PTME, with some ctenacanth genera including Amelacanthus surviving the entirety of the event and into the Early Triassic in refugia areas such as the waters of what is today Oman. Multiple lineages of cladodontomorphs also survived the PTME as indicated by additional post-PTME records of ctenacanths in Early Triassic deposits from the Bear Lake Area of Idaho, U.S. alongside potentially from the Vega-Phroso Siltstone Member of the Sulphur Mountains Formation of British Columbia, Canada. The Cladodontomorphs were able to survive the PTME by likely utilizing the deep oceans as specific zones of refugia, a hypothesis based on the discovery of Early Cretaceous cladodontomorphs in deep, outer shelf environments. Ichthyosaurs, which evolved immediately before the PTME, were also PTME survivors.

The Lilliput effect, the phenomenon of dwarfing of species during and immediately following a mass extinction event, has been observed across the Permian-Triassic boundary, notably occurring in foraminifera, brachiopods,bivalves, and ostracods. Though gastropods that survived the cataclysm were smaller in size than those that did not, it remains debated whether the Lilliput effect truly took hold among gastropods. Some gastropod taxa, termed "Gulliver gastropods", ballooned in size during and immediately following the mass extinction, exemplifying the Lilliput effect's opposite, which has been dubbed the Brobdingnag effect.