Platyctenids display widely differing morphological characteristics from their pelagic counterparts, being highly flattened on their oral-aboral axis and having lost many key traits associated with the phylum.

This has been supported by strong morphological and developmental data, specifically the sharing of what has been termed a "Cydippida-like" larva form in all 4 orders.

[1] Ranging in size 15 cm and below, they have dorso-ventrally flattened, oval and secondarily bilaterally symmetrical bodies.

All but one species of platyctenids lack the iconic ctene rows (the ciliated comb-rows) that distinguishes the ctenophores but they still possess the pair of tentilla-bearing tentacles and adhesive collocytes that also characterize the phylum in pores along the dorsal surface.

Sea Slug Forum, Australian Museum, Sydney 2)Eeckhaut, I., Flammang, P., Lo Bue, C., & Jangoux, M. 1997.

Functional morphology of the tentacles and tentilla of Coeloplana bannworthi (ctenophore, platyctenida), an ectosymbiont of Diadema setosum (echinodermata, echinoida).