Abstract:

Skulls of many living and extinct beaked whales (Ziphiidae) contain various bizarre bone and tooth structures. Many of them show sexual dimorphism in their skull anatomy: males have bizarre skull structures, whereas females do not. Opinions differ as to what the function of these structures might be. Some believe that these are weapons; others, that they are sound transmitters. This article argues that these structures are the means of visual display. Many of the bizarre bone structures of beaked whales are not exposed like ‘visuals’ of terrestrial tetrapods, but are located deep in soft tissues. Nevertheless, toothed whales recognize objects (including three-dimensional bodies), using echolocation. So, along with visual means, they can ‘see’ and ‘show’ their internal bone structures with echoic imaging and use them as informational sources in social interactions and in individual or species recognition.

I suspect some other basis.

As most people understand the word "dolphin", Orcas are not technically dolphins though they belong to the same family.

I've heard the claim that Orcas are a species of porpoise, like dolphins, but I can't even corroborate that since Wikipedia is claiming that porpoises are distinct from dolphins.

The clearest explanation I've been able to find comes from this article: https://nextlevelsailing.com/relationship-between-orca-kille...

> The classification of orcas as dolphins stems from their scientific categorization. Both orcas and dolphins fall under the family Delphinidae, which encompasses oceanic dolphins. Despite their formidable size and fearsome reputation, orcas share more in common with their smaller dolphin relatives than with other whale species.

So Orcas and dolphins are both categorized in the family Delphinidae which is colloquially referred to as the "Oceanic Dolphins" so, depending on what you mean, yes Orcas are technically dolphins but then ... so are dolphins. Meaning that "dolphin" and "delphinidae" refer to two distinct things even though all dolphins are delphinidae and the colloquial term for "delphinidae" is "oceanic dolphin." But it's important to recognize that the oceanic dolphins is a pretty wide family that includes several species that have the word "whale" in their name, such as belugas and narwhals, in addition to orcas.

More so than the lungs of other animals? Or is it just that "lungs" stand out as an unusual feature in that environment?