The Fossibles -- Bursting from Extinction to Distinction

Too few Permian diapsid fossils have been found to support any conclusion about the effect of the Permian extinction on diapsids the "reptile" group from which lizards, snakes, crocodilians, and dinosaurs including birds evolved. The groups that survived suffered extremely heavy losses of species, and some terrestrial vertebrate groups very nearly became extinct at the end-Permian.

Some of the surviving groups did not persist for long past this period, while others that barely survived went on to produce diverse and long-lasting lineages. An analysis of marine fossils from the Permian's final Changhsingian stage found that marine organisms with low tolerance for hypercapnia high concentration of carbon dioxide had high extinction rates, while the most tolerant organisms had very slight losses. The most vulnerable marine organisms were those that produced calcareous hard parts i. Close relatives without calcareous hard parts suffered only minor losses, for example sea anemones , from which modern corals evolved.

This pattern is consistent with what is known about the effects of hypoxia , a shortage but not a total absence of oxygen. However, hypoxia cannot have been the only killing mechanism for marine organisms. Nearly all of the continental shelf waters would have had to become severely hypoxic to account for the magnitude of the extinction, but such a catastrophe would make it difficult to explain the very selective pattern of the extinction.

Models of the Late Permian and Early Triassic atmospheres show a significant but protracted decline in atmospheric oxygen levels, with no acceleration near the P—Tr boundary. Minimum atmospheric oxygen levels in the Early Triassic are never less than present day levels—the decline in oxygen levels does not match the temporal pattern of the extinction. Marine organisms are more sensitive to changes in CO 2 carbon dioxide levels than are terrestrial organisms for a variety of reasons.

CO 2 is 28 times more soluble in water than is oxygen. Marine animals normally function with lower concentrations of CO 2 in their bodies than land animals, as the removal of CO 2 in air-breathing animals is impeded by the need for the gas to pass through the respiratory system's membranes lungs ' alveolus , tracheae , and the like , even when CO 2 diffuses more easily than oxygen. In marine organisms, relatively modest but sustained increases in CO 2 concentrations hamper the synthesis of proteins , reduce fertilization rates, and produce deformities in calcareous hard parts.

It is difficult to analyze extinction and survival rates of land organisms in detail, because few terrestrial fossil beds span the Permian—Triassic boundary. Triassic insects are very different from those of the Permian, but a gap in the insect fossil record spans approximately 15 million years from the late Permian to early Triassic.

The best-known record of vertebrate changes across the Permian—Triassic boundary occurs in the Karoo Supergroup of South Africa , but statistical analyses have so far not produced clear conclusions. Earlier analyses indicated that life on Earth recovered quickly after the Permian extinctions, but this was mostly in the form of disaster taxa , opportunist organisms such as the hardy Lystrosaurus. Research published in indicates that the specialized animals that formed complex ecosystems, with high biodiversity, complex food webs and a variety of niches , took much longer to recover.

It is thought that this long recovery was due to the successive waves of extinction, which inhibited recovery, and prolonged environmental stress to organisms, which continued into the Early Triassic. This explains why recovery took so long: During the early Triassic 4 to 6 million years after the P—Tr extinction , the plant biomass was insufficient to form coal deposits, which implies a limited food mass for herbivores.

Each major segment of the early Triassic ecosystem—plant and animal, marine and terrestrial—was dominated by a small number of genera , which appeared virtually worldwide, for example: A healthy ecosystem has a much larger number of genera, each living in a few preferred types of habitat. Disaster taxa took advantage of the devastated ecosystems and enjoyed a temporary population boom and increase in their territory.

Microconchids are the dominant component of otherwise impoverished Early Triassic encrusting assemblages. Lingula a brachiopod ; stromatolites , which had been confined to marginal environments since the Ordovician ; Pleuromeia a small, weedy plant ; Dicroidium a seed fern. Prior to the extinction, about two-thirds of marine animals were sessile and attached to the sea floor.

Permian–Triassic extinction event - Wikipedia

During the Mesozoic, only about half of the marine animals were sessile while the rest were free-living. Analysis of marine fossils from the period indicated a decrease in the abundance of sessile epifaunal suspension feeders such as brachiopods and sea lilies and an increase in more complex mobile species such as snails , sea urchins and crabs.

Before the Permian mass extinction event, both complex and simple marine ecosystems were equally common; after the recovery from the mass extinction, the complex communities outnumbered the simple communities by nearly three to one, [81] and the increase in predation pressure led to the Mesozoic Marine Revolution.

Bivalves were fairly rare before the P—Tr extinction but became numerous and diverse in the Triassic, and one group, the rudist clams, became the Mesozoic 's main reef-builders. Some researchers think much of this change happened in the 5 million years between the two major extinction pulses. Crinoids "sea lilies" suffered a selective extinction, resulting in a decrease in the variety of their forms.

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Smaller carnivorous cynodont therapsids also survived, including the ancestors of mammals. In the Karoo region of southern Africa , the therocephalians Tetracynodon , Moschorhinus and Ictidosuchoides survived, but do not appear to have been abundant in the Triassic. Archosaurs which included the ancestors of dinosaurs and crocodilians were initially rarer than therapsids, but they began to displace therapsids in the mid-Triassic. In the mid to late Triassic, the dinosaurs evolved from one group of archosaurs, and went on to dominate terrestrial ecosystems during the Jurassic and Cretaceous.

Some temnospondyl amphibians made a relatively quick recovery, in spite of nearly becoming extinct. Mastodonsaurus and trematosaurians were the main aquatic and semiaquatic predators during most of the Triassic , some preying on tetrapods and others on fish. Scientists have accumulated a fairly significant amount of evidence for causes, and several mechanisms have been proposed for the extinction event. The proposals include both catastrophic and gradual processes similar to those theorized for the Cretaceous—Paleogene extinction event.

Evidence that an impact event may have caused the Cretaceous—Paleogene extinction event Cretaceous—Tertiary has led to speculation that similar impacts may have been the cause of other extinction events, including the P—Tr extinction, and thus to a search for evidence of impacts at the times of other extinctions and for large impact craters of the appropriate age. Reported evidence for an impact event from the P—Tr boundary level includes rare grains of shocked quartz in Australia and Antarctica; [89] [90] fullerenes trapping extraterrestrial noble gases; [91] meteorite fragments in Antarctica; [92] and grains rich in iron, nickel and silicon, which may have been created by an impact.

The observed features were concluded to be not due to shock, but rather to plastic deformation , consistent with formation in a tectonic environment such as volcanism. An impact crater on the sea floor would be evidence of a possible cause of the P—Tr extinction, but such a crater would by now have disappeared. However, Earth's oldest ocean-floor crust is million years old because it is continually destroyed and renewed by spreading and subduction. Thus, craters produced by very large impacts may be masked by extensive flood basalting from below after the crust is punctured or weakened.

A large impact might have triggered other mechanisms of extinction described below, [] such as the Siberian Traps eruptions at either an impact site [] or the antipode of an impact site. The estimated energy released by the Araguainha impact is insufficient to be a direct cause of the global mass extinction, but the colossal local earth tremors would have released huge amounts of oil and gas from the shattered rock.

The resulting sudden global warming might have precipitated the Permian—Triassic extinction event. In May , Michael R.

Fossibles: Bursting From Extinction To Distinction by Heather Rancourt & Claudia Gauches

Rampino published an abstract for the American Geophysical Union noting the discovery of a circular gravity anomaly near the Falkland Islands. Estimates for the age of the structure range up to millions years old. However, Dave McCarthy and colleagues from the British Geological Survey not only illustrated that the gravity anomaly is not circular, but that the seismic data presented by Rocca, Rampino and Baez Presser did not cross the proposed crater, nor did it provide any evidence for an impact crater. The final stages of the Permian had two flood basalt events. A small one, the Emeishan Traps in China , occurred at the same time as the end- Guadalupian extinction pulse, in an area close to the equator at the time.

The Emeishan and Siberian Traps eruptions may have caused dust clouds and acid aerosols , which would have blocked out sunlight and thus disrupted photosynthesis both on land and in the photic zone of the ocean, causing food chains to collapse. The eruptions may also have caused acid rain when the aerosols washed out of the atmosphere.

That may have killed land plants and molluscs and planktonic organisms which had calcium carbonate shells. The eruptions would also have emitted carbon dioxide , causing global warming. When all of the dust clouds and aerosols washed out of the atmosphere, the excess carbon dioxide would have remained and the warming would have proceeded without any mitigating effects. The Siberian Traps had unusual features that made them even more dangerous.

Pure flood basalts produce fluid, low-viscosity lava and do not hurl debris into the atmosphere. In January , a team, led by Stephen Grasby of the Geological Survey of Canada—Calgary, reported evidence that volcanism caused massive coal beds to ignite, possibly releasing more than 3 trillion tons of carbon. The team found ash deposits in deep rock layers near what is now Buchanan Lake. According to their article, "coal ash dispersed by the explosive Siberian Trap eruption would be expected to have an associated release of toxic elements in impacted water bodies where fly ash slurries developed Mafic megascale eruptions are long-lived events that would allow significant build-up of global ash clouds.

Yang reported the total amounts of important volatiles emitted from the Siberian Traps are 8. In , evidence and a timeline indicated the extinction was caused by events in the Large igneous province of the Siberian Traps. Other hypotheses include mass oceanic poisoning releasing vast amounts of CO 2 [] and a long-term reorganisation of the global carbon cycle. At the right combination of pressure and temperature, it gets trapped in clathrates fairly close to the surface of permafrost and in much larger quantities at continental margins continental shelves and the deeper seabed close to them.

The area covered by lava from the Siberian Traps eruptions is about twice as large as was originally thought, and most of the additional area was shallow sea at the time. The seabed probably contained methane hydrate deposits, and the lava caused the deposits to dissociate, releasing vast quantities of methane. However, the pattern of isotope shifts expected to result from a massive release of methane does not match the patterns seen throughout the early Triassic. Evidence for widespread ocean anoxia severe deficiency of oxygen and euxinia presence of hydrogen sulfide is found from the Late Permian to the Early Triassic.

Their abundance in sediments from the P-T boundary indicates hydrogen sulfide was present even in shallow waters. This spread of toxic, oxygen-depleted water would have been devastating for marine life, producing widespread die-offs.

Models of ocean chemistry show that anoxia and euxinia would have been closely associated with hypercapnia high levels of carbon dioxide. Hypercapnia best explains the selectivity of the extinction, but anoxia and euxinia probably contributed to the high mortality of the event. The persistence of anoxia through the Early Triassic may explain the slow recovery of marine life after the extinction. Models also show that anoxic events can cause catastrophic hydrogen sulfide emissions into the atmosphere see below.

The sequence of events leading to anoxic oceans may have been triggered by carbon dioxide emissions from the eruption of the Siberian Traps. Increased weathering of the continents due to warming and the acceleration of the water cycle would increase the riverine flux of phosphate to the ocean. The phosphate would have supported greater primary productivity in the surface oceans. The increase in organic matter production would have caused more organic matter to sink into the deep ocean, where its respiration would further decrease oxygen concentrations. Once anoxia became established, it would have been sustained by a positive feedback loop because deep water anoxia tends to increase the recycling efficiency of phosphate, leading to even higher productivity.

A severe anoxic event at the end of the Permian would have allowed sulfate-reducing bacteria to thrive, causing the production of large amounts of hydrogen sulfide in the anoxic ocean. Upwelling of this water may have released massive hydrogen sulfide emissions into the atmosphere and would poison terrestrial plants and animals and severely weaken the ozone layer , exposing much of the life that remained to fatal levels of UV radiation.

The hypothesis has the advantage of explaining the mass extinction of plants, which would have added to the methane levels and should otherwise have thrived in an atmosphere with a high level of carbon dioxide. Fossil spores from the end-Permian further support the theory: Oceanic circulation and atmospheric weather patterns during the mid-Permian produced seasonal monsoons near the coasts and an arid climate in the vast continental interior of Pangaea.

The extent of biologically diverse and ecologically productive coastal areas shrank as the supercontinent formed. The elimination of shallow aquatic environments exposed formerly protected organisms of the rich continental shelves to increased environmental volatility. After the formation of Pangaea see the diagram "Marine genus biodiversity" at the top of this article , the rate of marine life depletion approached catastrophic levels; however, marine life extinction never reached the rate of the "Big Five" mass extinctions.

A hypothesis published in posits that a genus of anaerobic methanogenic archaea known as Methanosarcina was responsible for the event. That would have led to their exponential reproduction, allowing them to rapidly consume vast deposits of organic carbon that had accumulated in the marine sediment. Massive volcanism facilitated this process by releasing large amounts of nickel, a scarce metal which is a cofactor for enzymes involved in producing methane. Possible causes supported by strong evidence appear to describe a sequence of catastrophes, each worse than the last: However, there may be some weak links in this chain of events: From Wikipedia, the free encyclopedia.

Marine extinction intensity during the Phanerozoic.

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Millions of years ago. Plot of extinction intensity percentage of marine genera that are present in each interval of time but do not exist in the following interval vs time in the past. Calcified green algae return. Full recovery of woody trees [19]. An approximate timescale of events around the P-Tr boundary.

Human timeline and Nature timeline. Extinction events List of unconfirmed impact craters on Earth — for unconfirmed craters similar to or larger than Chicxulub Siberian Traps Wilkes Land crater. Fleur, Nicholas 16 February The New York Times. Retrieved 17 February Retrieved 1 April Guess what they find?

They manage to transport four very large eggs back to their home and decide to try to hatch them. Several days later, perched on a plant stand under bright lamps, in large bowls lined with towels, they do hatch. Joan and Clem become instant parents of four different types of dinosaurs! They name the tyrannosaur, Trex, the brontosaurus, Braun, the triceratops, Riz, and the parasaurolophus, Deb. There are some interesting, but highly unlikely things written into this story.

Could you buy Dino-Ade in modern day Arizona if no one but the Stone family knew that dinosaurs actually exist? Clem and Joan decide to take them to the cave where they found their eggs and there they discover yet another egg that they take home, and that hatches into their little brother, Little T: Anything is fossible, after all, in this story, including the fact that a professor is able to quit his job, move to Arizona, start a motorcycle repair shop, and is miraculously able to afford a acre property, an airplane hangar home for his five dinosaur children and to feed them all on his salary from fixing motorcycles.

I appreciate the magical intent in the story, of course, but it just seems a little too imfossible to be believed at times. Bursting From Extinction to Distinction was published in and is the first in a proposed series of books starring these superstar dinosaurs. Authors Heather Rancourt and Claudia Gauches have created a wonderful website to celebrate the Fossibles at http: The Fossibles series would have made a much better comic book than a short novel. Book 1 is glaringly void of regular illustrations although there are some really great pictures in a five page photo album at the end of the book that allow the reader to see what the characters look like, as well as on the website.

Oh—I hate 'To be Continued' endings. The cover is really cool though and I would probably pick it up on that alone! I remember seeing this book a while back, so it's nice to hear what it's about. I'm not fond of To Be Continued endings either, but that's what happens when you start to read a series!