Tutcetus: Dwarf Basilosaurid
It's funny, barely a week after the reveal of Perucetus, perhaps the largest known basilosaurid so far, we immediately see the description of what may be the smallest.
Tutcetus, named after child king Tutankhamun, is a new species of early whale that may have measured only 2.5 meters. Known from a single skull of what is thought to be a subadult at the very edge of maturity, it is also one of the oldest basilosaurids. The fossil was discovered in the famous Fayum Depression, i.e. one of the most important regions for early whale fossils.
While its generally hard to tell age, the stage of tooth replacement and the fusion of the skull bones indicate that Tutcetus was about to reach maturity, so it likely didn't grow much larger than indicated by the holotype fossil.
Tutcetus seems to be an early diverging basilosaurid (which is paraphyletic according to the authors), with its closest relatives being Ocucajea (a contemporary of Perucetus) and Chrysocetus.
Although our sample size is obviously low, the authors still tried their best to deduce some parts of its biology. For instance, they suggest that the small size of this animal might be related to the warmer temperatures of its time and that Tutcetus followed the mantra of "live fast, die young". They argue that Tutcetus, again based on how its teeth were replaced, matured quickly to reproduce sooner, while never reaching an especially old age. This would contrast later basilosaurids, which would grow slower, reach larger sizes and live longer. But of course more material would go a long way to confirm these suggestions.
