Resting zone, Proliferative zone, Hypertrophic cartilage zone, Calcified cartilage zone, Ossification zone. Calcified cysts have already died and involuted. The resulting emboli are pieces of calcified plaque. Plain abdominal radiographs may show the outline of an aneurysm when its walls are calcified. This may be calcified, forming structures such as shells, bones, and spicules. It was diagnosed as a calcified fibrosis tumor. The carapace is calcified to varying degrees in different crustaceans. Since their skeleton is not fully calcified, light can easily penetrate tissues. CT scan may reveal nonspecific calcified images in the tonsillar zone. Exoskeletons have evolved independently many times; 18 lineages evolved calcified exoskeletons alone. The calcified gland is often seen in skull x-rays. These fossils resemble calcified multicellular members of the Dasycladales. Calcified aptychi only occur in ammonites from the Mesozoic era. In sewers carrying alkaline fluids, lipids can become calcified and solidify. Sometimes the Nektaspida are included, but these lack a calcified exoskeleton and eyes.