What is not a unique anatomical feature of mammals that can be recognized in the fossil record?

Option A, Temporal fenestra

Explanation:

Complete question-

Which of the following is not a unique anatomical feature of mammals that can be recognized in the fossil record?

ANSWER

Temporal fenestra

A set of three bones—the hammer, anvil, and stirrup—that transmit sound in the middle ear

A lower jaw composed of a single bone

Teeth differentiated into incisors, canines, premolars, and molars

A dentary-squamosal hinge connecting the upper and lower jaws

Solution -

Temporal fenestra is a characteristic feature of skull of reptiles and some other animals. These are openings on the lateral side of skull that allow expansion and contraction of muscles. Mammals including human do not have temporal fenestra though they are descendants of synapsids whose fossils shows sign of presence of  temporal fenestra.

Rest all other features are visible in mammals of one or the other kind.

Hence, option A is correct