Which of the following is not classified as a eumetazoan?

Porifera, commonly known as sponges, are not classified as eumetazoans because they lack true tissues and symmetries that are characteristic of eumetazoans. Eumetazoans represent a more complex level of organization, with well-defined tissues that are organized into true organs and systems. Sponges are considered to be at a more primitive level of the animal kingdom, displaying a simple body plan that lacks specialized tissues and organs.

In contrast, Cnidaria, Lophotrochozoa, and Ecdysozoa all exhibit characteristics of eumetazoans, including the presence of true tissues. Cnidaria includes organisms like jellyfish and corals that possess specialized cells, such as cnidocytes, and exhibit radial symmetry. Lophotrochozoa and Ecdysozoa comprise diverse groups that include organisms with bilateral symmetry and organ systems, further illustrating their classification under eumetazoans.