Dinosaur age shark teeth discovery in Dutch Maastricht


Cretaceous fossil shark's tooth from the Dutch Maastricht ENCI quarry, photo by Frans Frenken

This photo by Frans Frenken shows a Cretaceous fossil shark‘s tooth from the Dutch Maastricht ENCI quarry.

Translated from Dutch ANP news agency today:

Old shark teeth in Limburg ENCI quarry

Five teeth of an extinct mackerel shark were found in the ENCI quarry in Maastricht. According to conservation organisation Natuurmonumenten the animal was about 4 to 5 meters long. It lived about 66 to 68 million years ago.

Just before the Cretaceous-Tertiary extinction event which killed the dinosaurs and many other animals.

South Limburg was then a shallow subtropical inland sea.

Mackerel shark

The triangular teeth are about 2.5 centimeters. The mackerel shark used to eat sea turtles, fish and other animals. The first tooth was accidentally found during a guided tour of Natuurmonumenten volunteers on 17 November. On December 1 someone else found four more shark teeth.

The ENCI quarry has been used since 1926 to extract limestone. That stopped this year. The area is now being transformed into a nature and recreation area, to be opened in 2020. In the limestone layers in the quarry are many remains of prehistoric animals, such as sea urchins, corals, cephalopods and seashells.

Fossils

Fossils are often found in the ENCI quarry, such as sea urchins, but also a gigantic dinosaur age marine predator, a mosasaur.

This dinosaur age shark species is called Squalicorax pristodontus.

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Megalodon sharks, killed by supernova before Ice Age?


This August 2018 video says about itself:

The Truth Behind Why Megalodon Went Extinct

The megalodon was an amazing, powerful animal, and is an incredible part of our planet’s history—but that’s all it is now, history. New finds mean that we’re still making discoveries about how it lived, its life cycle and evolution. It died out because environmental changes and competition meant it couldn’t catch enough food to sustain itself, and with the state of our oceans today there’s little evidence to believe it’d fare any better now. Rather than fantasizing and investing time into the megalodon as a myth, we should listen to the plight of other creatures that now swim in its place, and help protect them before it’s too late.

From the University of Kansas in the USA:

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

December 11, 2018

Summary: 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, professor emeritus of physics & astronomy at the University of Kansas. “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. There’s some debate about whether there was only one supernova really nearby or a whole chain of them. I kind of favor a combo of the two — a big chain with one that was unusually powerful and close. 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.”

Melott’s co-authors were Franciole Marinho of Universidade Federal de Sao Carlos in Brazil and Laura Paulucci of Universidade Federal do ABC, also in Brazil.

According to the team, other evidence for a series of supernovae is found in the very architecture of the local universe.

“We have the Local Bubble in the interstellar medium,” Melott said. “We’re right on its edge. It’s a giant region about 300 light years long. It’s basically very hot, very low-density gas — nearly all the gas clouds have been swept out of it. The best way to manufacture a bubble like that is a whole bunch of supernovae blows it bigger and bigger, and that seems to fit well with idea of a chain. When we do calculations, they’re based on the idea that one supernova that goes off, and its energy sweeps by Earth, and it’s over. But with the Local Bubble, the cosmic rays kind of bounce off the sides, and the cosmic-ray bath would last 10,000 to 100,000 years. This way, you could imagine a whole series of these things feeding more and more cosmic rays into the Local Bubble and giving us cosmic rays for millions of 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.

Indeed, a famously large and fierce marine animal inhabiting shallower waters may have been doomed by the supernova radiation.

“One of the extinctions that happened 2.6 million years ago was Megalodon,” Melott said. “Imagine the Great White Shark in ‘Jaws‘, which was enormous — and that’s Megalodon, but it was about the size of a school bus. 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.”

Prehistoric sharks of central North America


This 4 December 2018 video from the USA says about itself:

When Sharks Swam the Great Plains

If you’ve ever been to, or lived in, or even flown over the central swath of North America, then you’ve seen the remnants of what was a uniquely fascinating environment. Scientists call it the Western Interior Seaway, and at its greatest extent, it ran from the Caribbean Sea to the Canadian Arctic.

Bahamas sharks, ray video


This 21 October 2018 video says about itself:

In this episode of Blue World, Jonathan and Cameraman Bill are night diving with sharks in the Bahamas! And just for added fun, we are taking the Brave Wilderness team with us! It’s sharks after dark! And we witness a spectacular chase between a Lemon shark and a Southern Stingray.

JONATHAN BIRD’S BLUE WORLD is an Emmy Award-winning underwater science/adventure series featuring underwater cinematographer/naturalist Jonathan Bird.

Shark scales study helped by Alan Turing


This 1 July 2015 video from the USA says about itself:

The Math of Shark Skin

Emory math professor Alessandro Veneziani, an expert in fluid dynamics, draws inspiration from nature. The rough surface of shark skin, for instance, helps sharks move faster through the water. Mathematicians have developed an equation for how this roughness translates into less viscosity for a swimming shark. Veneziani has applied this knowledge to everything from swimsuit design to the study of human blood flowing through arteries, to help doctors devise the best strategies for treating aneurisms.

From the University of Sheffield in England:

Codebreaker Turing’s theory explains how shark scales are patterned

November 7, 2018

A system proposed by world war two codebreaker Alan Turing

The British government ‘rewarded’ Turing for helping to win the war against nazi Germany with homophobic persecution, killing him. Like they had done before to Irish author Oscar Wilde.

more than 60 years ago can explain the patterning of tooth-like scales possessed by sharks, according to new research.

Scientists from the University of Sheffield’s Department of Animal and Plant Sciences found that Turing‘s reaction-diffusion theory — widely accepted as the patterning method in mouse hair and chicken feathers — also applies to shark scales.

The findings can explain how the pattern of shark scales has evolved to reduce drag whilst swimming, thereby saving energy during movement. Scientists believe studying the patterning could help to design new shark-inspired materials to improve energy and transport efficiency.

Turing, forefather of the computer, came up with the reaction-diffusion system which was published in 1952, two years before his death. His equations describe how molecular signals can interact to form complex patterns.

In the paper, published today (7 November 2018) in the journal Science Advances, researchers compared the patterning of shark scales to that of chicken feathers.

They found that the same core genes underlying feather patterning also underlie the development of shark scales and suggest these genes may be involved in the patterning of other diverse vertebrate skin structures, such as spines and teeth.

Dr Gareth Fraser, formerly of the University of Sheffield and now at the University of Florida, said: “We started looking at chicks and how they develop their feathers. We found these very nice lines of gene expression that pattern where these spots appear that eventually grow into feathers. We thought maybe the shark does a similar thing, and we found two rows on the dorsal surface, which start the whole process.

“We teamed up with a mathematician to figure out what the pattern is and whether we can model it. We found that shark skin denticles are precisely patterned through a set of equations that Alan Turing — the mathematician, computer scientist and the code breaker — came up with.

“These equations describe how certain chemicals interact during animal development and we found that these equations explain the patterning of these units.”

Researchers also demonstrated how tweaking the inputs of Turing’s system can result in diverse scale patterns comparable to those seen in shark and ray species alive today.

They suggest that natural variations to Turing’s system may have enabled the evolution of different traits within these animals, including the provision of drag reduction and defensive armour.

Rory Cooper, PhD student at the University of Sheffield, said: “Sharks belong to an ancient vertebrate group, long separated from most other jawed vertebrates. Studying their development gives us an idea of what skin structures may have looked like early in vertebrate evolution.

“We wanted to learn about the developmental processes that control how these diverse structures are patterned, and therefore the processes which facilitate their various functions.”

Scientists used a combination of techniques including reaction-diffusion modelling to create a simulation based on Turing’s equations, to demonstrate that his system can explain shark scale patterning, when the parameters are tuned appropriately.

Mr Cooper added: “Scientists and engineers have been trying to create shark-skin inspired materials to reduce drag and increase efficiency during locomotion, of both people and vehicles, for many years.

“Our findings help us to understand how shark scales are patterned, which is essential for enabling their function in drag reduction.

Therefore, this research helps us to understand how these drag reductive properties first arose in sharks, and how they change between different species.”

Patterning is one important aspect that contributes to achieving drag reduction in certain shark species. Another is the shape of individual scales. Researchers now want to examine the developmental processes which underlie the variation of shape both within and between different shark species.

“Understanding how both these factors contribute towards drag reduction will hopefully lead towards the production of improved, widely applicable shark-inspired materials capable of reducing drag and saving energy”, added Mr Cooper.

Shark evolution, new research


This June 2017 video is called The Evolution of Sharks.

From the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan:

Getting a grip on the slow but unique evolution of sharks

October 8, 2018

Scientists at the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan, in collaboration with other Japanese institutes and aquariums, have decoded the whole genomes of two shark species for the first time and improved the whale shark genome sequences released previously. By analyzing the genomes and comparing them with those of other vertebrate species, they have constructed an overview of their unique life histories and evolutionary paths. This work was published online in Nature Ecology and Evolution.

Advances in genome sequencing have made it possible to compare genomes from different species, giving us insights into their evolutionary histories and characteristics. While data for many organisms are available, to date, genome sequencing for sharks has been hampered by their huge genomes, which are even larger than the human genome. The notable exception is the elephant shark, although strictly speaking this fish is not professionally classified as a true shark.

Sharks have many unique characteristics, including their body structures, reproductive systems, way of sensing, and extreme longevity — a shark species is known to live for more than three centuries. Fully decoded shark genomes will be a tremendous help to research aimed at discovering the molecular bases for these qualities. With this ultimate goal in mind, a research team led by Shigehiro Kuraku at RIKEN BDR analyzed shark genomes using cutting-edge DNA sequencing technologies and comparative bioinformatics that were able to deal with gigabase-scale sequences. They chose two primary species — the brownbanded bamboo shark and the cloudy catshark — because they can be raised in aquariums, making it relatively easy to constantly obtain live specimen. They also performed an improved assembly of the whale shark genome, which had been previously released.

One of the puzzles regarding sharks is why their genomes are so large. The team found that the large genome size is due to massive insertions of repetitive elements. At the same time, shark genomes have been evolving slowly, which means that they have kept many ancestral gene repertoires and can be thought of as “living fossils” in a genomic sense.

The team found that sharks have counterparts of human genes regulating growth, reproduction, and homeostasis, such as obesity, appetite, and sleep, suggesting that elements of our molecular machinery for basic physiology have existed for more than 450 million years, before sharks split from our common ancestors.

The newly decoded shark genomes have already provided a number of insights, including those related to visual function. The researchers analyzed light absorption of visual pigments in the whale shark and found that its rhodopsin pigment is tuned to sense relatively short wavelengths of lights — close to 480 nm — that can penetrate deep-sea water. This is not true in its close relative the bamboo shark, and the researchers speculate that the altered rhodopsin function is related to the unique lifestyle of the whale shark, which dives down to about 2000 m when not feeding near the surface. This discovery was achieved by combining DNA sequence analysis and laboratory work using synthesized materials, but without animal experiments.

The team also showed that all three of the analyzed shark species have relatively few olfactory receptor genes, implying that they depend on other systems, such as sensing electromagnetic fields, for navigation.

“Our results will fill a long-standing gap in the genome biology of animals, and will also help us gain greater understanding about metabolism, reproductive cycle, and health monitoring of sharks,” says Keiichi Sato, an author and the deputy director of Okinawa Churaumi Aquarium. “Such understanding should contribute to the conservation of marine environments as well as to sustainable husbandry and exhibitions at aquariums that allow everyone to experience biodiversity up close.”