What do vertebrates have that distinguishes them from other animals?

Vertebrates are primarily characterized by having a bony or cartilaginous skeleton, which serves not only as a support structure for the body but also protects vital organs, including the brain and spinal cord. This skeletal framework is integral to the vertebrate's overall body plan and allows for greater complexity and mobility than is typically seen in invertebrates. The backbone or vertebral column, which is part of the skeleton, provides significant stability and allows for the development of a more advanced nervous system and muscle coordination.

The presence of a bony or cartilaginous skeleton is a defining feature that sets vertebrates apart from other animal groups. Other animals may have different skeletal structures or none at all, such as soft-bodied organisms. For example, many invertebrates possess exoskeletons or hydrostatic skeletons instead of an internal skeleton like that of vertebrates.

While a segmented skeleton and a notochord are features associated with certain animal groups, they are not unique to vertebrates alone. The notochord, while it is present in all embryonic stages of vertebrates, is also found in some invertebrate chordates. Similarly, a large brain enclosed in a skull is a characteristic of vertebrates, but not all