Pliocene Marine Megafauna Extinction

[EnolaGaia]

A new extinction incident has now been identified and described ...

Nearly One-Third of Ocean Animals Perished 2.6 Million Years Ago

... The largest known shark that ever lived, Carcharocles megalodon, ruled the seas for over 20 million years. The enormous toothy predator, which could grow to about 60 feet long, seemed indestructible. ...

"Megalodon lived all around the world, during a time in which the oceans were warmer than today," biologist and marine species specialist Catalina Pimiento said. "Our research suggests it was a cosmopolitan giant shark that was able to live in different latitudes, as ocean temperature didn't determine its distribution. We also know it used shallow water productive areas as nurseries."

Life appeared to be pretty good for this dominant apex predator, until disaster struck. Pimiento and an international team of researchers determined that megalodon did not die out alone. When the gigantic shark went extinct around 2.6 million years ago, so too did a third of all other large marine species. The previously unknown "Pliocene marine megafauna extinction" is described in the journal Nature Ecology & Evolution.

Pimiento conducted the research at the Paleontological Institute and Museum of the University of Zurich with her colleagues John Griffin, Christopher Clements, Daniele Silvestro, Sara Varela, Mark Uhen, and Carlos Jaramillo. The team made their determinations after a meta-analysis that looked at numerous prior studies concerning the fossil record of sharks, marine mammals, sea birds, and sea turtles. ...

The scientists found that, in addition to megalodon, species of big sea cows and baleen whales also went extinct 2-3 million years ago. As many as 43 percent of sea turtle species, 35 percent of seabirds and 9 percent of sharks also died out at this time.

The drivers of the die-out are not precisely known, but the researchers note that violent sea level fluctuations coincided with the extinction event. Coastal habitats were significantly reduced as a result. Marine mammals that megalodon feasted on started to decline, while new competitors evolved. ...

SOURCE: https://www.livescience.com/59624-ancient-mass-extinction-of-ocean-animals.html

 

[EnolaGaia]

Here's the abstract for the cited report ...

The end of the Pliocene marked the beginning of a period of great climatic variability and sea-level oscillations. Here, based on a new analysis of the fossil record, we identify a previously unrecognized extinction event among marine megafauna (mammals, seabirds, turtles and sharks) during this time, with extinction rates three times higher than in the rest of the Cenozoic, and with 36% of Pliocene genera failing to survive into the Pleistocene. To gauge the potential consequences of this event for ecosystem functioning, we evaluate its impacts on functional diversity, focusing on the 86% of the megafauna genera that are associated with coastal habitats. Seven (14%) coastal functional entities (unique trait combinations) disappeared, along with 17% of functional richness (volume of the functional space). The origination of new genera during the Pleistocene created new functional entities and contributed to a functional shift of 21%, but minimally compensated for the functional space lost. Reconstructions show that from the late Pliocene onwards, the global area of the neritic zone significantly diminished and exhibited amplified fluctuations. We hypothesize that the abrupt loss of productive coastal habitats, potentially acting alongside oceanographic alterations, was a key extinction driver. The importance of area loss is supported by model analyses showing that animals with high energy requirements (homeotherms) were more susceptible to extinction. The extinction event we uncover here demonstrates that marine megafauna were more vulnerable to global environmental changes in the recent geological past than previously thought.

SOURCE: http://www.nature.com/articles/s41559-017-0223-6

 

[EnolaGaia]

This newly published research suggests Megalodon was partially doomed by an unusually high metabolism and body temperature, making it vulnerable to sea temperature rises occurring at the time of the Pliocene Marine Megafauna Extinction.

Super-Steamy Megalodon May Have Been Too Hot to Avoid Extinction
Why did the monster shark megalodon go extinct? New research has answers, and the shark's high body temperature may have played a part. ...

Fearsome though this giant predator was, it disappeared from the oceans about 2.6 million years ago. And new research looked to the body temperature of Otodus megalodon to offer an explanation for what may have caused it to die out.

Like some other sharks alive today, such as great white and mako sharks, megalodon is thought to have been able to thermoregulate, or adjust its body temperature in response to cooler or warmer water. This would have enabled it to hunt in a broader range of habitats than other sharks, according to research presented today (Dec. 10) at the annual meeting of the American Geophysical Union (AGU).

But was megalodon's body temperature similar to that of modern sharks? To find out, scientists used geochemistry to examine rare carbon and oxygen isotopes in megalodon teeth and in teeth of modern sharks. ...

Their preliminary results suggested that megalodon was "quite warm" for a shark ... Ancestors of today's makos and great white sharks that swam alongside megalodon millions of years ago likely had body temperatures of about 68 to 86 degrees Fahrenheit (20 to 30 degrees Celsius).

By comparison, megalodon may have been running a body temperature as high as 95 to 104 degrees F (35 to 40 degrees C), which is the body temperature of whales, Griffiths said.

With such a high body temperature, megalodon must have had a very active metabolism that required frequent feeding ... Then, the climate warmed, and megalodon's prey moved to cooler waters at higher latitudes. Food scarcity and competition from new predator species such as killer whales may then have been the fatal combination that drove megalodon to extinction, Griffiths explained. ...

FULL STORY: https://www.livescience.com/64274-megalodon-shark-body-temperature.html

 

[EnolaGaia]

Coincidentally, this other newly emergent study suggests muon radiation from one or more supernovae would have doomed the larger marine fauna - either directly via radiation exposure or indirectly via climatic influence(s).

Did supernovae kill off large ocean animals at dawn of Pleistocene?

The effects of a supernova -- and possibly more than one -- on large ocean life like school-bus-sized Megalodon 2.6 million years ago are detailed in a new article.

About 2.6 million years ago, an oddly bright light arrived in the prehistoric sky and lingered there for weeks or months. It was a supernova some 150 light years away from Earth. Within a few hundred years, long after the strange light in the sky had dwindled, a tsunami of cosmic energy from that same shattering star explosion could have reached our planet and pummeled the atmosphere, touching off climate change and triggering mass extinctions of large ocean animals, including a shark species that was the size of a school bus.

The effects of such a supernova -- and possibly more than one -- on large ocean life are detailed in a paper just published in Astrobiology.

"I've been doing research like this for about 15 years, and always in the past it's been based on what we know generally about the universe -- that these supernovae should have affected Earth at some time or another," said lead author Adrian Melott ...

"This time, it's different. We have evidence of nearby events at a specific time. We know about how far away they were, so we can actually compute how that would have affected the Earth and compare it to what we know about what happened at that time -- it's much more specific."

Melott said recent papers revealing ancient seabed deposits of iron-60 isotopes provided the "slam-dunk" evidence of the timing and distance of supernovae.

"As far back as the mid-1990s, people said, 'Hey, look for iron-60. It's a telltale because there's no other way for it to get to Earth but from a supernova.' Because iron-60 is radioactive, if it was formed with the Earth it would be long gone by now. So, it had to have been rained down on us. ... If you look at iron-60 residue, there's a huge spike 2.6 million years ago, but there's excess scattered clear back 10 million years." ...

Whether or not there was one supernova or a series of them, the supernova energy that spread layers of iron-60 all over the world also caused penetrating particles called muons to shower Earth, causing cancers and mutations -- especially to larger animals.

"The best description of a muon would be a very heavy electron -- but a muon is a couple hundred times more massive than an electron," Melott said. "They're very penetrating. Even normally, there are lots of them passing through us. Nearly all of them pass through harmlessly, yet about one-fifth of our radiation dose comes by muons. But when this wave of cosmic rays hits, multiply those muons by a few hundred. Only a small faction of them will interact in any way, but when the number is so large and their energy so high, you get increased mutations and cancer -- these would be the main biological effects. We estimated the cancer rate would go up about 50 percent for something the size of a human -- and the bigger you are, the worse it is. For an elephant or a whale, the radiation dose goes way up."

A supernova 2.6 million years ago may be related to a marine megafaunal extinction at the Pliocene-Pleistocene boundary where 36 percent of the genera were estimated to become extinct. The extinction was concentrated in coastal waters, where larger organisms would catch a greater radiation dose from the muons.

According to the authors of the new paper, damage from muons would extend down hundreds of yards into ocean waters, becoming less severe at greater depths: "High energy muons can reach deeper in the oceans being the more relevant agent of biological damage as depth increases," they write. ...


"One of the extinctions that happened 2.6 million years ago was Megalodon," Melott said. " ... They just disappeared about that time. So, we can speculate it might have something to do with the muons. Basically, the bigger the creature is the bigger the increase in radiation would have been."

The KU researcher said the evidence of a supernova, or series of them, is "another puzzle piece" to clarify the possible reasons for the Pliocene-Pleistocene boundary extinction.

"There really hasn't been any good explanation for the marine megafaunal extinction," Melott said. "This could be one. It's this paradigm change -- we know something happened and when it happened, so for the first time we can really dig in and look for things in a definite way. We now can get really definite about what the effects of radiation would be in a way that wasn't possible before."

FULL STORY: https://www.sciencedaily.com/releases/2018/12/181211112941.htm

 

[hunck]

This newly published research suggests Megalodon was partially doomed by an unusually high metabolism and body temperature, making it vulnerable to sea temperature rises occurring at the time of the Pliocene Marine Megafauna Extinction.

FULL STORY: https://www.livescience.com/64274-megalodon-shark-body-temperature.html

Conversely, this article from the Natural History Museum implies it became extinct in a period of global cooling..

We know that megalodon had become extinct by the end of the Pliocene (2.6 million years ago), when the planet entered a phase of global cooling. Precisely when the last megalodon died is not known, but it was between 3.6 and 2.6 million years ago.

Scientists think that up to a third of all large marine animals, including 43% of turtles and 35% of sea birds, became extinct as temperatures cooled and the number of organisms at the base of the food chain plummeted, resulting in a knock-on effect to the predators at the top.

The cooling of the planet may have contributed to the extinction of the megalodon in a number of ways.

As the adult sharks were dependent on tropical waters, the drop in ocean temperatures likely resulted in a significant loss of habitat. It may also have resulted in the megalodon's prey either going extinct or adapting to the cooler waters and moving to where the sharks could not follow.

 

[EnolaGaia]

Coincidentally, this other newly emergent study suggests muon radiation from one or more supernovae would have doomed the larger marine fauna - either directly via radiation exposure or indirectly via climatic influence(s). ...

Recently published research seems to have confirmed that there was a supernova explosion in our cosmic vicinity circa 2.5 million years ago. The confirmation is based on discovery of a manganese isotope that could only have been created in a supernova event. The earlier known iron isotope that suggested a possible close supernova in that timeframe was not so uniquely tied to a supernova for its origin.

We Now Have Proof a Supernova Exploded Perilously Close to Earth 2.5 Million Years Ago

Among all of the hazards that threaten a planet, the most potentially calamitous might be a nearby star exploding as a supernova.

When a massive enough star reaches the end of its life, it explodes as a supernova (SN). The hyper-energetic explosion can light up the sky for months, turning night into day for any planets close enough.

If a planet is too close, it will be sterilized, even destroyed. As the star goes through its death throes, it produces certain chemical elements which are spread out into space.

For years, researchers have puzzled over evidence that a supernova exploded somewhere in Earth's vicinity a couple of million years ago. The evidence is a concentration of 60Fe, an isotope of iron produced by supernovae, found around the Earth.

Now, a new study presents additional evidence of a supernova explosion near Earth 2.5 million years ago. This time, it's a concentration of 53Mn, another radioisotope produced by supernovae. ...

The study is centered on what are called ferromanganese crusts. They're made of rock, but look more like chocolate cake. They're deposits of marine sediments that grow over time, as iron and manganese oxides precipitate out of the seawater.

They keep a record of the chemicals in the source water as they form over time. Besides being a potential source of valuable minerals, they're also valuable evidence for scientists. The team of researchers behind this study examined samples of these ferromanganese crusts and found not only 60Fe, but also 53Mn. ...

The 60Fe found on the Earth is potential evidence of a supernova explosion in Earth's rough vicinity. 60Fe is known as an extinct radionuclide. Because its half life is 2.6 million years, any 60Fe on Earth should have decayed into nickel long ago. Finding it now means it was produced in more recent times, in astronomical terms.

But supernovae aren't the only thing that can synthesize 60Fe. It can also be produced by asymptomatic giant branch (AGB) stars. All stars in the low to intermediate mass range (0.6 to 10 solar masses) go through this stage of evolution near the end of their lives.

So it's possible that the 60Fe found on Earth came from one of these within the last few million years, rather than a supernova. How can the question of the source of the 60Fe be answered?

In their paper the researchers write that "An unambiguous, only SN formed radionuclide, such as 53Mn, detected in the same samples as the 60Fe, can solve this open question."

Now scientists have found 53Mn in the same ferromanganese crusts as the 60Fe. Unlike 60Fe, 53Mn can't be produced by AGB stars. It can only be produced by supernovae. ...

FULL STORY:
https://www.sciencealert.com/a-supernova-exploded-dangerously-close-to-earth-2-5-million-years-ago

PUBLISHED RESEARCH ARTICLE:

Supernova-Produced 53Mn on Earth
G. Korschinek, T. Faestermann, M. Poutivtsev, A. Arazi, K. Knie, G. Rugel, and A. Wallner
Phys. Rev. Lett. 125, 031101 – Published 17 July 2020
DOI:https://doi.org/10.1103/PhysRevLett.125.031101

ABSTRACT: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.031101

 

[Kondoru]

So, wheres the Nebula?

 

[EnolaGaia]

So, wheres the Nebula?

There may not be one. Depending on the destructiveness of the supernova event there may be little or nothing left after more than 2 million years. This is also enough time lapse for any ionization that may have rendered the supernova's remnants visible to have dissipated.