These photos come to us from Steve Ballwanz, via Paul Murdoch. Steve found this specimen in the Miocene Kirkwood Formation in New Jersey. In this view (the lateral side of the tooth) it appears to be a typical tooth from a type of toothed whale called a squalodont. But if we turn the tooth over and look at its inside (medial) surface, it gets strange…
This tooth has a third root, which is very unusual in a Miocene whale. Squalodonts and a few other Miocene whales have two roots on each back tooth, but most Miocene whales (and all living ones with teeth) have only single-rooted teeth. Here is what a normal squalodont tooth looks like (this is a tooth from the Smithsonian Institution’s collection):
The right image above is the medial side of the tooth; notice that there is no big bulge on it.
I have seen squalodont teeth with three roots, but the third root is generally small and doesn’t much affect the shape of the crown, which is normally a flat triangular blade. But in this tooth, even the crown is affected, as you can see when the tooth is viewed from the tip:
In spite of its unique shape, I believe this is a squalodont tooth. Third roots are a primitive feature in whales, and they still occasionally showed up in squalodonts all the way up to their extinction around 14 million years ago. Other than the extra root and its associated features, everything about this tooth looks like a squalodont. I think this tooth is atavistic, a throwback to the primitive three-root condition.
Thanks to Steve and Paul for sending us photos of this unique specimen.
Update: It turns out the tooth probably came from Eocene rather than Miocene sediments, and after seeing these images Mark Uhen and Richard Hulbert suggested that the tooth looks like a protocetid whale, which is consistent with the apparent Eocene age.