#basilosauridae

I know I usually talk about crocs, but this is too good not to share. A new giant basilosaurid whale with weird anatomy from the Eocene of Peru. Perucetus colossus is a peculiar animal. It's bones were incredibly thick and incredibly dense, very much unlike those of modern whales and even more extreme than even those of the thicker basilosaurids (aptly named Pachycetinae i.e. thick whales). These adaptations have been compared to modern manatees and dugongs. Know the weight range is highly dependent on what you base the math on. Using manatees as a proxy, you get a weight of "only" 85 tons....using extreme values for whales a whopping 340 tons. Mean values for whales a still really big 180 tons. This could indicate that Perucetus rivaled the Blue Whale as the worlds heaviest animal ever.

The ecology is poorly understood tho. We know basilosaurids preferred coastal waters, and with all the similarities to manatees it is reasonable to assume that Perucetus was a shallow water animal itself. It also likely wasn't the fastest swimmer. And the lack of a skull basically means we can't say much on its diet. We can wager a guess and say it wasn't a predator because, you know....it also likely wasn't a grazer. Cool as it would be, we don't really have herbivorous whales like that so its incredibly unlikely. The two more likely suggestions are that it lived on small animals burried in the ocean floor, sorta like a grey whale. Or that it was a scavenger like a sleeper shark (tho I find that suggestion far less likely, giving me scavenging T.rex vibes ngl). But again, once we get a skull we can talk about this better.

Sidenote I do find the name a little underwhelming. It's a bizarre animal and the best we could come up with is "Colossal whale from Peru". I'm also not a mammal person, but from what I'm being told the silhouette is a little exaggerated and it wasn't necessarily that thick in life.

While I work on getting my major projects to a stage where I think they're worth sharing, here's some very loose sketches of five Archaeocetes staring straight down the camera, obviously looking most dignified from this angle. Drawn from memory, probably not quite accurate, nonetheless fun.

hello basilosaurid nation i have been thinking about the perucetus colossus and his tiny little legs !

Anyway, pls enjoy this BasilACEsaur!!!

While last week's Tutcetus was the smallest known basilosaurid whale, another recently-announced member of that group was almost the complete opposite.

Perucetus colossus was a chonker. An absolute unit of a whale.

Living during the Eocene (~38 million years ago) in shallow marine waters covering what is now the coast of Peru, this ancient whale is known from several vertebrae, ribs, and parts of its pelvis. As a result its full size is uncertain, but based on the proportions of other basilosaurids it was probably somewhere around 17-20m long (~56'-66') – similar in length to the larger specimens of Basilosaurus.

However, it had much thicker denser bones, even more so than those of its close relative Antaecetus, suggesting that its full body mass was much higher than the rather slender Basilosaurus – and possibly heavier than even modern blue whales despite being shorter in overall length.

Perucetus' thickened vertebrae were also fairly inflexible in most directions, indicating it was a sirenian-like slow swimmer with limited maneuverability – but it did have a surprisingly good ability to bend its body downwards. Without skull material it's unclear what its diet was like, but it may have been a suction-feeder hoovering up seafloor prey like modern grey whales or walruses.

I've reconstructed it here with a speculative bristly fleshy downturned snout inspired by the weird skull of Makaracetus, an earlier whale that may have also been a walrus-like bottom-feeder.

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