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.
parts of sharks that fossilize - types of shark fossils Introduction to Shark Fossils Because sharks are made of cartilage and not bone, it's a common misconception that teeth are the only parts that fossilize. Although shark teeth are by far the most common fossils, many other parts of sharks fossilize.