a body cavity that most animals possess

One body cavity that most animals possess is the coelom. The coelom is a fluid-filled cavity lined with mesoderm that surrounds and protects the internal organs. It provides space for organs to move and grow without disrupting each other, and it also acts as a shock absorber. The coelom is found in most animal phyla, including mammals, birds, reptiles, amphibians, and many invertebrates.