Turrilites (Turrilites) costatus is a species of helically coiled ammonoid cephalopod, from the lower part of the Upper Cretaceous (Cenomanian).

The shell of this species can reach a length of about 11 centimetres (4.3 in).

It is tightly wound in a high trochospiral, with an acute angle at the apex.

Ribs are weak, with rows of strong tubercles.