#toothed whale

Modernbeluga whalesandnarwhals are the only living representatives of the monodontid lineage, found only in cold Arctic and sub-Arctic waters. But this whale family actually first evolved in much warmer climates – and some of them were downright tropical.

Casatia thermophila lived about 5 million years ago during the early Pliocene, in the Mediterranean SeaaroundTuscany, Italy. Although known only from a couple of partial skulls and a few vertebrae it was probably similar in size to its modern relatives, around 5m long (16'4").

It seems to have had a larger number of functional teeth than modern monodontids, and probably didn’t suction feed like its modern close relatives. Instead it may have fed more like most porpoises and dolphins, relying more on speed and snapping jaws to capture prey.

It inhabited the Mediterranean at a time not long after the sea there had mostly dried up and then been rapidly refilled. The presence of warm-water marine species such as bull sharks,tiger sharks, and dugongs in the same fossil beds as Casatia indicates the local climate at the time was hotter than it is today, with tropical temperatures – and suggests that this whale’s ancestors must have originally moved into the replenishing Mediterranean from lower latitudes alongside these other warmth-adapted animals.

This tropical monodontid was also much closer related to modern belugas than modern narwhals are, which raises the possibility that the two living monodontid species actually specialized for colder conditions completely independently of each other rather than descending from a cold-adapted common ancestor. Instead modern belugas and narwhals may have originated from separate warm-water monodontid ancestors who evolved similar cold-tolerant adaptations in parallel as the climate cooled during the onset of the Quaternary ice age, while the rest of their relatives all went extinct.

———

Nix Illustration|Tumblr|Twitter|Patreon

Hi guys, another long silence I know. It’s busy with the train driver’s course - on top of regular driving I’ve had training for and taken a couple more exams (all passed, thankfully). It’s coming to an end though - within a few months I should be driving independently! Looking forward to it, as well as being able to pick up drawing again.

To show I’m not dead, here’s some more illustrations from last year’s big commission: the sperm whale. Males are quite differently proportioned from females, most notably that huge head! On big bulls it can be almost 1/3 of their total length - I’ve kept it a bit more modest here because at some point it just starts looking wrong to me lol. I’m very pleased with how these came out. I feel I’ve never managed to get sperm whales right, but these two are much more to my satisfaction (especially the female). Couldn’t resist putting some elaborate markings on the male because they are just so pretty. I hope you’ll like these swimming sonar-boosters too!