MANFRED KAGE / SCIENCE PHOTO LIBRARY MANFRED KAGE / SCIENCE PHOTO LIBRARY
Ammonite fossil. Section through the shell of an ammonite fossil. Ammonites were marine invertebrates. Within the shell are progressively larger chambers separated by thin walls. As the ammonite grew it added new larger chambers to the shell, only occupying the last chamber. Ammonites first appeared in the fossil record around 400 million years ago in the late Silurian and early Devonian periods and became extinct at the end of the Cretaceous period, 65 million years ago. Ammonites are index fossils, their presence allows the rock layer in which they are found to be dated to specific geological time periods.
Model release not required. Property release not required.