![]() ![]() Images adapted from Benton & Harper, 2013. Dotted lines represent no evidence to prove existence of common ancestor. Phylogenetic tree depicting relationships amongst cephalopods with stratigraphic ranges Ammonoidea is more closely related to the coleoids as compared to Nautiloidea. Ammonites were believed to be petrified snakes and were fitted with carved heads to be sold to pilgrims during the medieval times. Their shells are index fossils for stratigraphy due to their easy identification, rapid evolution and being discovered on many types of marine sedimentary rocks with global geographic distribution. Ammonites faced extinction after three catastrophic events during the Permian, Triassic and end of the Cretaceous, which coincided with that of dinosaurs in the Cretaceous-Palaeogene (K-Pg) event. Nautiluses originated from the Ordovician period (approximately 450 million years ago) wheres ammonites first appeared during the Permian period (approximately 240 million years ago). In contrast to popular belief, ammonites and modern coleoids are more closely related as compared to the extant nautilus. Nautiluses are often compared with ammonites due to numerous morphological similarities. Evolutionary relationship with ammonites! Interesting facts about this unique creature!Ģ.1. Allonautilus perforates (Conrad, 1847).Ģ.Allonautilus scrobiculatus (Lightfoot, 1786).The Chambered Nautilus ( Nautilus pompilius) is of particular interest, being the largest and most prevalent nautilus known to exist! There were approximately 10,000 species in prehistoric times but only six extant species in the Nautilidae family remain as of today. These marine creatures have dominated the ancient oceans before the realm of fishes arose, and even before the first dinosaurs appeared. Commonly referred to as the “living fossils”, nautiluses had originated and virtually unmodified over the last 450 million years. Nautiluses are cephalopods (Greek for “head-foot” due to tentacles attaching to the head) that are closely related to the coleoids such as octopus, cuttlefish and squid. It is the source of all true art and science." - Einstein, Albert. Just as with sunflowers and succulent plants, the pattern of seeds on a sunflower can be found in repeating sunflowers in either clockwise or counter-clockwise motion.The most beautiful thing we can experience is the mysterious. ![]() ![]() (images via: daniel oines, wikimedia commons) The repeating golden spiral can be found within the petals of a rose. This shape helps collect sound waves and direct them to the inner ear. The Human EarĮven the human ear conforms to the shape of the golden spiral. The golden spiral is highlighted in this image of a leaf from a bromeliad plant. When cut in half, a nautilus shell displays its chambers and its spiral structure becomes even more apparent. Sea shells are among the most striking examples of the golden spiral at work. (images via: sudhamshu, wikimedia commons, bernadettemacphersonmorris)Įven certain species of spiders form their webs in spirals that closely approximate the golden spiral. Isn’t it striking how similar they are? While galaxies and hurricanes may not seem to have much in common, they both exhibit the mathematical curve of a logarithmic spiral. Look at the images of the galaxies compared to this satellite image of Hurricane Isabel. It may not be as evident as the other examples at first, but the spines on this cacti have grown in the same spiral pattern as the sunflowers and succulents. It works to the plant’s advantage by preventing new leaves from blocking older leaves’ access to sunlight, directing the maximum amount of rain and dew to the roots. Plants grow new cells in spirals, which is how this pattern appears. (images via: art poskanser, duff_sf, randy robertson)Įven succulent plants like aloe display the golden spiral with amazing perfection. Here is the Fibonacci spiral in the swirl of a galaxy, just as it appears in so many other natural forms. For a sunflower, growing in this manner creates the most compact pattern possible with no gaps from beginning to end. This amazingly complex layout of seeds is a perfect example of the golden proportion in nature. Look closely at the center of a sunflower and you’ll see the golden spiral in a repeating pattern. (images via: nickton, wikimedia commons 1 + 2) ![]()
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