The story of the phragmocones. Brief introduction to ammonites.
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- Опубликовано: 21 июл 2024
- As a true Nature’s work of art, ammonites are beautiful and each one is unique.
The useful links:
problem of dimorphism in ammonites (pdf file):
"palaeontologia.pan.pl/Archive/..."
Stone-on-stone technology to ignite fire:
"www.primitiveways.com/marcasit..."
Ammonites in folklore:
"depositsmag.com/2016/09/27/fo..."
The ammonites were mollusks from a group called cephalopods. The name cephalopods reflects the fact that these animals had tentacles attached to their heads. Modern day cephalopods are Nautilus, squid, octopuses and cuttlefish. By the way, scientists believe that the soft bodies of the ammonites resembled squids more that those of the living fossil Nautilus (no’-tee-lus), which is considered evolutionary less advanced than ammonites. Ammonites supposedly had 8 arms arranged in pairs, along with 2 longer tentacles.
The shell of an ammonite consisted of a living chamber, where the body of the mollusk resided, and a spiral part with multiple chambers. This part is called phragmocone. In most cases, the living chamber is destroyed leaving only phragmocone to be preserved as a fossil. So, we are actually looking at broken shells no matter how beautiful they are.
The function of the phragmocone was to enable the ammonite to float. The chambers were filled with a mix of gas and fluids making the average density the whole animal similar to that of water and creating so called buoyancy. The gas inside the chambers is likely formed through a process similar to the one observed in sparkling water and is controlled by the exchange of sodium and chloride ions across the wall of siphuncle. The siphuncle is a tiny tube running through all the chambers of the phragmocone.
It is an important feature of the chambered shells allowing the mollusks to adjust their buoyancy.
One of the key differences between nautiloids and ammonoids is that nautiloids had a so called median siphuncle, which was located right in the center of the chambers while ammonites had a lateral siphuncle located at the external edge of the spiral shell.
The walls separating chambers inside the shell are called septa, septum if singular. They can be slightly curved but in many instances have a wavy and branchy structure.
Here is a fragment of baculite, an ammonite with a straight shell. The specimen has empty chambers and well-preserved septa, which creates a labyrinth inside the shells, which by the way was originally made from a material called aragonite. In this specimen fossilized aragonite has a light brown coloration. Who knows how it was colored when the animal was alive? Supposedly it had some sort of stripes to camouflage the mollusks from the predators like marine reptiles.
The pattern of septa is a feature of paramount importance for the classification of the ammonites. Nautiloids always have plain, concave septa, and if you see complex patterns of the septa you can be sure that this is an ammonite. Look at the intricate design of septa revealed after the layer of mother of pearl was removed. The fossilized mother of pearl can be quite colorful and iridescent. This mineral is called ammolite and is advertized as one of the rarest gemstones on Earth. It’s been commercially mined in Canada but you can get a glimpse of it in specimens from other localities like Madagascar or Russia. It resembles opal due to light diffraction that separates colors of incident light in a rainbow-like fashion. Some books mention differences between the shells of a male and a female ammonoids but it’s really hard to prove this theory. In fact, Paleontological records are fragmentary and, as a result, female and male specimens can be easily described as two different species. This may happen and to animals fossilized at different developmental stages or even different parts of the same animal. There is just no way to know unless some rare specimen is discovered and new information is taken into account.
Nevertheless, careful and meticulous studies can reveal some hints based on the frequency association of shells with different exterior morphology and common features in internal structure. The general consensus is that female ammonites were larger than males to accommodate development of eggs. Scientists also look for the changes in the growth pattern associated with breeding cycles of females. To make things more complicated, a few species of cephalopods developed 2 distinct types of males within one species. Those may differ in size and mating behavior.
The ammonoids as well as modern nautiloids were predatory and fed on shrimp-like crustaceans and probably crabs.
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I absolutely adore your program it is so nice to see a young person taking time to share their wealth of information with everyone else. Keep up the good work young lady
Thanks, Joe! Much appreciated.
You have a good collection of ammonites. I like this video.
You are a very good teacher, Koi..! I learned a lot about this topic..! Thank you..!!!
Hi! I'm glad it was useful to you.Thanks for watching and commenting.
Thanks, Koi. I learned a lot and it was helpful to know about the ammolite/fossilized mother of pearl ammonite I just bought. Thank you again!
Gorgeous and informative video👍
Thank you, Michael!
Thank you so much for this information! I found one but it broke into 4 pieces when I dropped it. I'm trying to get a museum to analyse it for me.
Thanks for the comment. Good luck with the fossil identification.
GREAT VIDEO!!
Thank you.
You're welcome!
What do you do to stabilize fossils? I've heard of it but don't know what it is. I have an ammonite that I want to prep. Also, how do you get the beautiful colors to show? You are so smart, I bet you the answer for me. Your channel is so informative, keep it up.
Hi Rod, it depends on the mineral composition of the fossil. Most frequently, people would like to know how stabilize pyrite ammonites, which loose their color and even disintegrate under humid conditions due to oxidation (FeS2+O2=FeSO4). For an ordinary collector, the best way to preserve such a fossil by soaking it in the paraffin.
You would need to clean the fossil from dirt with a slightly alkali solution (a little bit of laundry detergent). It's better to be done soon after the fossil is extracted from the ground and still "wet". Heat and dry the sample for 20-40 min in an oven or under lamp (no more than 100oC, you should be able to handle it while it's warm). Let the fossil stay in dry place for few days to allow it to dry completely. Get a piece of paraffin and shave off small pieces. Put them into a pan with the fossil. Boil 2-4 min and watch how small air bubbles leaving the fossil (paraffin will replace air and protect the fossil from oxidation). Take the pan off the fire (stop heating) once paraffin starts boiling too strongly (with large bubbles). Take out the hot fossil using forceps and clean up extra paraffin. Be careful. Cover with a hair spray (hair lacquer) and then (after drying) with colorless nail polish (cover first one side of the fossil and then another side). Hair spray is needed to help with sticking nail polish to the paraffin. The procedure may change the hue/coloration of the fossil. The people who developed the technique mentioned that it works best for freshly excavated fossils. It you see white dust covering the pyrite and indicating corrosion, it is likely hopeless. Practice on unimportant piece first to test and improve the technique. Below is the link to the source of the information. My dad happen to know one of the authors via few collaboration on fossils and art related matters. So, he mentioned the article to me.
www.ginras.ru/p-science/files/nelihov_rogov2008_ammonit.pdf
The non-pyrite ammonites are mostly polished. This is what brings out the color in the vast majority of lapidary samples. Good luck and thanks for watching.
@@KOIstories Thanks!