Ancient baleen whales had a mouth full of teeth

[Still Waters]

A strange phenomenon happens with modern blue whales, humpback whales and gray whales: they have teeth in the womb but are born toothless. Replacing the teeth is baleen, a series of plates composed of thin, hair- and fingernail-like structures growing from the roof of their mouths that act as a sieve for filter feeding small fish and tiny shrimp-like krill.

The disappearing embryonic teeth are testament to an evolutionary history from ancient whales that had teeth and consumed larger prey. Modern baleen whales on the other hand use their fringed baleen to strain their miniscule prey from water, hence the term filter feeding.

A new study that utilized high-resolution computed tomography (CT) to scan a 25 million year-old fossil whale skull found neurovascular evidence that Aetiocetus weltoni, an evolutionary "cousin" of today's baleen whales (Mysticeti), had both teeth and baleen simultaneously in adulthood, making for a very crowded mouth.

https://phys.org/news/2021-05-dental-crowding-ancient-baleen-whales.html

https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlab017/6278618

[+OverSword]

I wonder if orcas or dolphins will eventually follow this evolutionary path?