Micrornatus hopwoodi was a small mackerel-like predator known from a single three-dimensional London Clay skull. Modern re-examination of the specimen has clarified details that distinguish it from other early scombrids, including the structure of the skull roof and ethmoid region. Its slender teeth indicate a fish that grasped small mobile prey rather than crushing hard food.

The presence of a pineal opening and the arrangement of the frontal bones preserve primitive cranial features within an otherwise scombrid-like head. Because the species is known from one skull, ecological statements should remain modest, but an active pelagic or near-pelagic predatory role is consistent with both its anatomy and relationships.