Hesperornis(diving bird)
Fish eaterLandNot rideable
Hesperornis avenatantes. Flippant
Method
Cannot be tamed
There is no way to tame this.
Taming
Hesperornis has no taming data on the wiki, so there is nothing to calculate. That usually means it cannot be tamed at all, but it can also mean the numbers have not been published yet.