The phyla that have only two tissue layers are called diploblastic. These are the Cnidaria and Ctenophora.

Here's a breakdown:

* Cnidaria: This phylum includes jellyfish, corals, sea anemones, and hydras. They are characterized by radial symmetry, a sac-like body with a single opening (mouth/anus), and specialized stinging cells called nematocysts.

* Ctenophora: This phylum includes comb jellies, which are free-swimming, gelatinous animals with eight rows of cilia for locomotion. They are also radially symmetrical and have a two-layered body.

Important Note:

While these phyla only have two primary germ layers (ectoderm and endoderm), they do possess specialized cells that carry out functions usually associated with tissues found in more complex organisms.

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