In vertebrate paleontology, CT (computed, computer, or computerized tomography) is a technology that allows highly detailed images inside fossils that are encased in matrix or other obstruction via the use of harmless (to the fossil) x-rays. This technique is vital for use in vertebrate paleontology because specimens are often described on the basis of a single fossil, which is usually precious and irreplaceable. This technology has been used to uncover internal structures that were previously unknown to science, as well as helping to determine the evolutionary and phylogenetic placement of specific animals.