Phytnatodermais a complex, branching biogenic structure that is seldom mentioned in the ichnologic literature, although it may have been misidentified recently as“Zonarites”and large pellet‐filled“Chondrites”.The ichnogenus is usually interpreted as the product of subsurface deposit‐feeding animals. Well‐preserved examples from Pliocene slope mudstone in Ecuador are assignable toP. granulatum(Schlotheim, 1822). These structures are typically 30–40 cm in overall diameter; consist of outward‐branching, horizontal to subhorizontal, overlapping tunnels grouped in bundles; and have tunnel fills consisting of pelleted volcanic ash. The EcuadorianPhymatodermaoccur with a moderately rich ichnoassemblage that includesAlcyonidiopsisichnosp.,Chondrites intricatus, several kinds ofPhycodes‐likestructures,Phycosiphon incertum, Planolitesichnosp.,Rorschachichnus amoeba, Scoliciaichnosp.,Taenidium barretti, andZoophycosichnosp. Benthic foraminiferids and geologic context point to deposition on the upper trench slope, ca. 3–4 Ma.