ammonites

Superb #emericiceras #barremense #ammonite.These #cretaceous period #fossils once filled the ancient seas over what is now North Africa. Termed heteromorphs the ammonites started an evolutionary path uncoiling out of the #logarithmic spiral forms, eventually almost becoming a walking stick form, see previous post. #fossilsale #spiral #helices #involute #evolute These ammonites became #extinct around 74 million years ago, while a cousin the #nautilus is #extant. Science has not yet found the answer to that intriguing question. Yet!?! Our latest collection arrived from North Africa last week.

What happens when @etherealcandy and @crystallistener force me to go rock shopping on my day off 🙊😂

SUPER excited about:
Tourmalinated Quartz
Opalized Ammonite (fossil)
Kunzite
Moonstone
Rutilated Smoky Quartz
Tumbled Shungite


••••••••¥••••••••

#seaox #crystal #crystals #jewelry #quartz #crystalhealing #crystalenergy #yoga #meditation #wicca #wiccan #newage #quartzcrystal #bohemian #vsco #vscocam #natural #beautiful #gypsy #bohochic #boho #nature #instagood #ootd #photooftheday #jotd #etsy #gemstone #chakra #healing (at Seaoxdesigns.com)

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We sell a lot of these cut and polished ammonite fossils from Madagascar, but I think this 6 inch wide pair is particularly interesting.  It has some brilliant purple coloration, which I’ve only seen in a few of them.  The inner chambers of these 110 million year old fossil cephalopods has been filled in with a silica based material, more commonly referred to as being “agatized”  Check them out at FossilEra.com

The purple color is likely a product of manganese compounds being present in the silica (quartz/agate) that filled in the chambers.

Ammonites are a group of ancient mollusks related to modern animals like nautiluses, which most closely resemble their extinct cousins, squid, and octopuses. Ammonites were a phenomenally successful group, branching out into a wide variety of distinct species and diverse forms all over the world’s oceans, where they endured for more than 300 million years. They also had hard shells—most frequently coiled, though some species sported spiral helices and U-shaped shells—and hard jaws, an extraordinary number of which survived as fossils. The Museum's invertebrate fossil collection, one of the largest in the world, has more than 2 million ammonite specimens. (The recently accessioned Mapes Collection of marine fossils, which pushed the Museum’s total holdings past 33 million specimens and artifacts last year, added about 150,000 more.)

Their abundance, broad geographic distribution, and a lengthy but limited stay on the planet make ammonites very useful markers of geologic time. They’re also great indicators of ancient climate. Ammonite shells and jaws consist mostly of calcium carbonate, the same substance that makes up the tiny shells of foraminifera. Depending on the temperature of the surrounding water when it forms, calcium carbonate contains different amounts of two oxygen isotopes. The ratio of these isotopes, says Neil Landman, curator in the Division of Paleontology, make the shells “very sensitive indicators of the environments and temperatures in which they were formed.” And since shells from one period can be compared against those from another, they can be used to track changes in climates over time. 

Ammonite shells could provide other clues about the ancient world as well. The fossil record shows that the first ammonites appeared during the Devonian period, around 400 million years ago. After thriving in ancient oceans for hundreds of millions of years, nearly all ammonites fell victim to the mass extinction at the end of the Cretaceous period that also wiped out the dinosaurs and more than half the species on the planet.

“Ammonites are everywhere toward the end of the Cretaceous period,” says Landman. “There’s no decrease in the number of individuals or the number of species leading up to their sudden disappearance.”

Their vanishing act can tell us more about the event that killed off so many forms of life, which is why Landman studies ammonite fossils that occur at the Cretaceous-Paleogene (K/Pg) boundary—the thin slice of geologic time immediately after the extinction.

This slice is found in just a few dozen places around the world, including sites in Morocco where Landman and colleagues traveled on a recent Constantine S. Niarchos expedition. Working with local geologists and university professors, Landman and other Museum paleontologists conducted the first big survey for ammonites around the K/Pg boundary in sedimentary rock layers on Morocco’s eastern coast. The result was a treasure trove of fossilized ammonites.

“We knew ammonites existed in this area,” Landman says. “But there is not much information known or published about them in this site.” The new specimens from the Moroccan expedition are still being studied, and Landman expects several papers will come out of the research. In addition to ammonites, the team gathered new specimens of foraminifera to add to the Museum’s collection and looked at levels of the element iridium, which was scattered across Earth during the meteorite impact, in samples of surrounding sediment.

Previous studies of ammonites have produced one consistent finding with implications for ocean life today. On the Cretaceous side of the K/Pg Boundary, ammonites are plentiful, while related nautilids are less common. After the extinction event, ammonites mostly disappear, while nautilid populations persist, largely unaffected. Their fates, Landman suggests, could have been clinched by the animals’ respective life cycles.

Ammonites hatched very small—less than a millimeter in diameter for some species—and would have made their homes among plankton and similar creatures in warm surface waters. Nautilids, meanwhile, were born larger and would have spent more time in deeper waters. If a meteorite impact caused rapid acidification of surface waters around the world, as some suggest, that would explain why ammonites, which used those waters as a kind of crib, would have been devastated, while young nautilids could have soldiered on through the catastrophe, sheltered in deeper water. 

As today’s oceans become increasingly acidic due to climate change, learning more about the ammonite extinction is more than an academic concern. The details of the catastrophe that struck 65 million years ago could inform how we deal with similar environmental issues in the modern era.

“Calcium carbonate shells on modern animals are getting thinner, and some evidence suggests the calcium carbonate spikes of sea urchins are getting smaller as well,” Landman says. “Understanding how ocean acidity affects marine species is very pertinent to where we are today.”

Learn about foraminifera, another group of creatures that are teaching us about climate change

An agatized ammonite fossil that has been polished so that the inner chambers are visible at the same time as the suture pattern.  An absolutely beautiful specimen, that provides a interesting look at the internal structure of this prehistoric animal.  

These ammonites are from the Cretaceous period, approximately 110 million years old and quarried from near Tulear, Madagascar.  Ammonites are an extinct group of marine invertebrate animals which died out at the end of the Cretaceous period. These mollusks are closely related to living coleoids (i.e. octopuses, squid, and cuttlefish)

This specimen was just added for sale at: https://www.fossilera.com/fossils/4-wide-polished-ammonite-dish-thick

X-ray vision: how did extinct marine creatures live?

Analysing fossils with modern imaging methods

Ammonites first made an appearance on Earth approximately 400 million years ago. Just like mussels and snails, they are classified as Mollusca. At first glance, there is a resemblance between ammonites and snails as the visceral mass of both species is concealed in a helical shell. However unlike marine snails, which crawl over the seabed, ammonites were able to use their shell for swimming; according to one theory anyway. Dr René Hoffmann from the Institute of Palaeontology wants to know if this is how it really was. To this end, he applies a method that is typically utilised in the field of medicine: namely computer tomography (CT).

Read more

Photos credit: Damian Gorczany, René Hoffmann (via RUBIN Science Magazine)

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Fossils at Monmouth Beach. Lyme Regis, Dorset. We were all so excited over these! So many happy memories from my childhood, and hopefully making happy memories for my children. It was so amazing to be in a place that helped to change history so spectacularly. You can almost feel the fin de siecle anxiety in the air, see the Victorians walking on the beach, see Hardy thinking up that passage in A Pair of Blue Eyes, Mary Anning finding her fossils. And you just can’t get it into your head that you’re looking at creatures that are hundreds of millions of years old. It’s too big to grasp.

(I have over 150 of these photos. Be grateful you only got 10.)

It’s a special cephalopodweek edition of Fossil Friday!

These are the extinct cephalopods known as ammonites. They inhabited the planet for more than 300 million years—almost twice as long as dinosaurs—before disappearing in the mass extinction event more than 65 million years ago. As many as 10,000 species may have existed, ranging from tiny organisms that measured only a fraction of an inch across to formidable animals more than 2 feet (0.6 meters) in diameter. Diverse, widespread, and abundant in their marine environments, ammonites left behind an extraordinary number of fossils.

©AMNH/S. Thurston

Happy Cephalopod Week!

This is a 170 million year old (Middle Jurassic) ammonite fossil, Parkinsonia parkinsoni, from Bridport, England. This particular specimen was on display during the 1893 World’s Fair here in Chicago. 

Ammonites – an extinct group of cephalopods – had series of chambers in their shells which could be filled with gas. A pump ran through these various pockets that allowed the animal to fill the chambers with water in order to control its own buoyancy! 

This photo is courtesy of our collections manager of fossil invertebrates, Paul Mayer. He regularly posts cool images like this to the Field’s Facebook. :)