|Squalicorax bites on the top of the skull|
|That's a nice set of ribs|
|Lower jaws, slender and displaying symmetrical tooth replacement|
|Nearly complete axis showing beefiness|
The differences really are amazing. A few years back, Takuya Konishi split Platecarpus planifrons into its own genus: Plesioplatecarpus. I was very skeptical of this split for a long while, but now after comparing the low chalk mosasaur against its upper chalk relative, I'm really beginning to see his point.