Perucetus colossus Size Chart

Finally managed to get my computer out to submit this thing!

So, Perucetus, often questioned as potentially the largest whale, is indeed a true colossus. Heavier than a Blue Whale? Well, this is where things get interesting.

Instead of having "normal" bones like any other tetrapod that ever existed, Perucetus has bizarre fat bones. The ribs look like sausages. The vertebrae look like fat pastries or some inflatable pool toy, or really fat star anise pods.

Needless to say, it's going to be a VERY heavy animal, and also VERY thickly built besides (the ribs suggest a thick girthy body; meaning we have an animal that's easily as long as Basilosaurus, but as fat as the larger Baleen Whale species... and would certainly weigh FAR more for its size.

As a result, instead of having a nice, simple task of sizing up normal-looking bones and guessing the weight, the researchers who described this specimen had the herculean task to to draw upon really dense, heavy marine animals (like the manatee) to offset what would certainly be massive size under-estimates if they relied on normal, light whale bones alone. Assuming this animal was a hugely chonked up and elongated Cynthiacetus (very likely), the end result was a massively broad potential weight range- from at least about the size of a Sperm Whale or Argentinosaurus, to at most, some of the upper Blue Whale masses. A big range for sure, but given how no other animal is remotely close to Perucetus, a pretty good guess.

Ignoring the definite density skewing the weight, it's still a massive whale; certainly larger than any other marine animal of similar length, and probably heavier than the average blue whale.... though Antarctic Blue Whales were still about 10 meters longer, and had at least a similar body girth.

Making this I scaled up the hypothetical skeleton to match the dimensions of the vertebrae, and missing parts inferred from a scaled, superimposed a photo of Cynthiacetus (scaled to match chest girth- which coincided with matching pelvic dimensions, and a cranial length slightly larger than presented- I also assumed similar cervical scale and form, so my version has a longer neck). Everything else I just erred to the reconstruction presented by the researchers.