Sinonyx jiashanensis (Zhou et al. 1995; late Paleocene, 55 mya; 28 cm skull length) was also originally considered a mesonychid, and the resemblance is indeed remarkable. Here Sinonyx nests within the tenrec/whale clade. It had 11 teeth (x4) including 4 blunt molars and a tall sagittal crest over the narrow cranium.
Wikipedia reports that scientists once thought of Sinonyx as a whale ancestor, but now consider artiodactyls close to hippos as whale ancestors. Those scientists were right the first time. In Sinonyx the entire bulla (ball enclosing the tiny ear bones) had become ossified, as it is in all whales.
An entire Sinonyx museum mount skeleton is shown online here, but I cannot verify its veracity in the literature, which only details the skull at present.