Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland.In contrast to excretion, the substance may have a certain function, rather than being a waste product.ecretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland.
The oldest shark fossils. The oldest fossilized evidence of prehistoric sharks comes from shark-like scales that date to 455 million years ago during the Ordovician Period, in Colorado. Some paleontologists do not agree that these scales are sufficiently shark-like to pronounce them sharks.
The Megalodon, Carcharodon megalodon, was largest shark of all time. It lived from the late Oligocene to early Pleistocene epochs, 20 to 1.5 million years ago. This giant of a shark was a huge version of the current great white shark. The word megalodon is a Greek word and means big tooth. Megalodon had teeth, which are among the largest ever found, over 18 cm long. The are believed to be as long as 16 meters and weigh over 60 tons. Megalodon hunted large and medium-sized whales, attacking the bony areas, such as chest or fins. This would stop the whale, or it could kill quickly with a fatal bite to the chest region. Megalodon could bite with the one of the strongest bites in the animal kingdom's history. The skeleton of a Megalodon was made of cartilage, so it will be impossible to find complete remains of these animals. Megalodon teeth, however were bone and can be found in all oceans, which shows that the sharks were all over the world.