The starfish belongs to the phylum Echinodermata, that is, a class of echinoderms, and belongs to a very representative group among them. Most echinoderms have some common features, such as their adult body is five radially symmetrical, for example, their body surface has some prominent spines and so on.
As an echinoderm, starfish also conform to the above basic characteristics. Their appearance is more familiar to us, is pentagonal star, the body is relatively flat, mostly five radiation symmetry; In addition, there are some spines on the surface of their bodies, which belong to the protuberances of their bones. It can be seen that starfish is a representative echinoderm with many common characteristics of echinoderms.
As mentioned above, starfish are echinoderms, so they are not mammals. Echinoderms belong to invertebrates, which are relatively advanced among invertebrates. But mammals belong to vertebrates, which are relatively advanced in vertebrates. Echinoderms and mammals do not intersect and should not be confused.
The differences between echinoderms and mammals are very large. For example, most mammals use viviparous reproduction and lactation, but starfish, as echinoderms, use different reproductive methods, requiring frequent oviposition, fertilization and other processes. Moreover, the way they breathe is also different, mammals generally have lungs, and use lungs to breathe; But as echinoderms, starfish have different respiratory organs, called gills.
