PLACENTICERAS MEEKI
The representative fossil of the ammonites displayed in the Earth Sciences Museum of the University of Waterloo is the Placenticeras Meeki.
Oxygen is a biolimiting element for metazoans and is an important factor that affects the species diversity and abundance of marine life. Like many species of ammonites that had an oxygen-dependent lifestyle, Placenticeras Meeki inhabited higher zones of water. To provide evidence of this, oxygen and carbon isotope analyses have shown that there are significant reduced salinities of the surface waters where P. Meeki used to reside. It is unfortunate that this crucial adaptation also led to their downfall. They are very well known to have been strongly attacked in shallow, surface waters by predators. These predators were the now-extinct mosasaurs.
FUN FACT: It has been suggested that the link between ammonite shell morphology and position in the water column gives us a useful tool in interpreting fluctuations in oxygen levels in marine depositional systems
Shell characteristics of P. Meeki are a complicated suture, low sutural amplitude index and a low resistance to hydrostatic pressure.
An aritistic representation of the mosasaurs which ravaged P. Meeki
AMMOLITE: THE PRICELESS BEAUTY
Fossils serve an educational role in paleontology, but their aesthetic beauty and rarity make it very popular to the public eye.
Ammolite is an opal-like organic gemstone that is mainly found in the Rocky Mountains from Alberta to Saskatchewan, and extends south to Montana. It is the fossilized remains of the ammonite shell, or casts of the interior of the shell. Ammolite usually refers to gems cut from those shells with an iridescent layer. The layers are 0.1-0.3mm thick after polishing, which is sufficiently thick and durable enough to be manufactured into jewelry. It is one of three organic gemstones (the others being amber and pearl).
Like the pearl, ammolite shell is made up of mostly aragonite. There are also trace amounts of aluminum, barium, chromium, copper, iron, magnesium, manganese, silicon, strontium, titanium and vanadium.
The property that allows us to see the incredible array of colors across its surface is iridescence. The shell’s surface is composed of closely packed, tabular, crystals of aragonite. They are united into thin plates or scales.
The thickness of these lamellae is simliar to the wavelengths of the spectral colors that make up white light. As a result, when white light (sunlight) enters the consistently spaced thin layers of aragonite, diffraction occurs and flashes of spectral colors are seen. the color depends on the angle of light and the onlookers perspective. Sometimes a subtle chromatic shift occurs. In this video, it is monochromatic meaning that the shift is limited to hue within the same primary color. There are many patterns that Ammolite shells can display, including moonglow, pinfire, and Nipplites
The color depends on the angle of light and the onlookers perspective. Sometimes a subtle chromatic shift occurs. In this video, it is monochromatic meaning that the shift is limited to hue within the same primary color.
