A starfish is neither a fish nor a mammal; it is an echinoderm.
Starfish, also known as sea stars, belong to the class Asteroidea and are marine invertebrates. Unlike fish, which are vertebrates with a backbone, starfish lack a skeleton made of bones. Instead, their bodies are supported by a hard calcium carbonate skeleton and are covered with a spiny skin.
Starfish are distinct from mammals as well. Mammals are warm-blooded animals that have fur or hair and typically give live birth. In contrast, starfish have a radically different physiology and reproductive methods, often relying on external fertilization and occasionally regenerating lost limbs.
In summary, starfish are unique creatures that do not fit into the categories of fish or mammals, highlighting the incredible diversity of life in our oceans.