The claim that mammals are the only animals with outer ears or pinnae is false, as certain insects such as katydids and bush-crickets also possess cuticular flaps functioning as auditory pinnae.
The claim asserts that only mammals possess outer ears or pinnae. However, retrieved papers explicitly describe auditory pinnae in non-mammalian taxa, specifically insects like katydids and bush-crickets. Therefore, the claim is clearly refuted by the evidence.