#physeteroidea

Kogiopsis floridana was a physeteroid whale that lived near the coast of the southeastern United States from the mid-Miocene to the early Pliocene, about 14-4 million years ago.

Known just from fossilized lower jaws and teeth, with some teeth up to nearly 13cm long (~5"), its full life appearance and size are uncertain – but it may have been slightly larger than a modern bottlenose dolphin at around 4.5m long (~14'9"). It's traditionally been considered to be part of the kogiid family, closely related to modern pygmy and dwarf sperm whales, but some studies disagree with that classification and instead place it in the true sperm whale lineage.

It was probably a predator in a similar ecological role to modern orcas, adapted for hunting prey like squid, fish, and smaller marine mammals. But unlike orcas it wouldn't have been the apex predator of its ecosystem, subject to predation pressure by even larger carnivores like macroraptorial sperm whales and everyone's favorite ridiculously huge shark – and as a result it probably had a "live fast and die young" lifestyle similar to modern kogiids and other small-to-medium-sized Miocene physeteroids, rapidly maturing and only living to around 20 years old.

I've reconstructed Kogiopsis here as a kogiid-like animal, with a similar sort of shark-like head shape and "false gill" markings. In the background a second individual is depicted displaying "inking" behavior, releasing a defensive cloud of reddish-brown fluid from a specialized sac in its colon.

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Sperm whale (Physeter macrocephalus)

The modern sperm whale is already an impressive animal, being by far the largest of the living toothed whales and famous for its ability to dive over 2km down (1.2 miles) to feed on deep-sea animals like giant squid.

But some of its ancient relatives were terrifying.

Livyatan melvillei here has an appropriately monstrous name, inspired by both the Hebrew name for the Leviathan and Herman Melville, the author of Moby-Dick. Known from the Pacific coast of South America during the late Miocene, around 10-9 million years ago, it's estimated to have measured somewhere between 13.5m and 17.5m long (~44'-57') – comparable in size to an adult male sperm whale.

Unlike the relatively slender mouth of its modern cousin, however, it instead had thick strong jaws full of enormous teeth.

Livyatan melvillei skull by Ghedoghedo | CC BY-SA 4.0 (for an idea of the sheer size of this reconstructed skull – some of those teeth are almost the length of your forearm)

It was part of a loose grouping of what are known as "macroraptorial sperm whales", which all had similarly toothy jaws and occupied the same sort of ecological niche as modern orcas, specializing in hunting prey like large fish, squid, seals, and other whales.

Livyatan's main food source was probably smaller baleen whales about half its own size, and its only real competition for this prey was the equally huge megalodon shark that shared the same waters.

A huge fossil tooth found in Australia suggests that Livyatan or a very close relative of it survived at least into the early Pliocene, about 5 million years ago. Around this time a cooling climate and dwindling numbers of its preferred prey would have eventually made a population of such enormous apex predators unsustainable, and driven this "killer sperm whale" into extinction – probably around the same time megalodon disappeared, about 3.6 million years ago.

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Sperm whale (Physeter macrocephalus)

Sperm whale (Physeter macrocephalus)

Dwarf sperm whale (Kogia simus)

The dwarf sperm whale inhabits temperate and tropical oceans worldwide, in particular continental shelves and slopes. It was first described by biologist Richard Owen, in 1866. The species was considered to be synonymous with K. breviceps from 1878 until 1998. Its appearance is very similar to the K. breviceps, distinguished mainly by the position of the dorsal fin on the body, which is nearer the middle on K. simus. The dwarf sperm whale is a suction feeder that mainly eats squid, and does this in small pods of typically 1 to 4 members. It is preyed upon by the killer whale and large sharks such as the great white shark. When startled, the whale can eject a cloud of red-brown fluid, similar to a squid. The dwarf sperm whale is hunted in small numbers around Asia. It is more threatened by ingesting or getting entangled by marine debris. No global population estimate has been made, and so its conservation status by the IUCN is data deficient.

Classification Animalia - Chordata - Mammalia - Eutheria - Boreoeutheria - Laurasiatheria - Scrotifera - Euungulata - Artiodactyla - Artiofabula - Cetruminantia - Whippomorpha - Cetacea - Odontoceti - Physeteroidea - Kogiidae - Kogiinae - Kogia - K. simus