Tectocarya grandis was an early Eocene mastixioid plant known from a thick, one-seeded fruit stone. Its hard endocarp protected the seed and was organised into distinct fibrous layers around a curved seed cavity. The parent plant itself is not preserved with these fruits, so its exact growth form and ecology remain unknown.

The most distinctive part of the fruit lies inside the stone: a median wall of fibres divides the deep dorsal infold. This separates Tectocarya from superficially similar Diplopanax material and shows why internal anatomy can be more informative than external shape in London Clay fruits.