Hi Scott,
I have been very interested in the teeth at Bakersfield (STH) for the past three years and have come to several conclusions about the identification process of planus and hastalis. (For what it’s worth)
- Planus uppers and hastalis uppers are pretty distinguishable, but even that can be a little confusing when some of the laterals are taken individually.
- When it comes to lowers, then the difficulty becomes tenfold. I have read accounts from museum literature to guides to STH identification stating that there is no difference when it comes to lowers, and that they are the same in both species.
Now, I’m going to stop right here for a moment and say that Bill Heim, who is a good and extremely respected friend of mine, and has already commented before me, is as brilliant as anyone in observing the smallest details in distinguishing shark teeth. I would hang my hat on what he says, but to most mortals some of the ID process is a very difficult and uncertain task.
What makes it even more confusing is that, to my knowledge, no associated dentition of C. planus exists or has ever been discovered. There are composite dentitions but without at least one associated C. planus to compare, then one is simply relying on the preparers imagination of what it might be. From a scientific standpoint I find that to be a real problem. If one takes a large random collection of mixed hastalis and planus uppers and lowers, it seems to me that that it would be very difficult to decide what differences constitute differences between species and what is genetic diversity within the same specie. Then ask yourself what are tooth location differences in the mouth within the same individual. Then ask the same question between different individuals within the same specie, or ask again between species and you load up your problems to even greater uncertainty. The more I look at the two species, the more difficult I find that it is to be sure of what exactly you are identifying in many cases, especially within the lowers. Like I stated earlier, upper anteriors and most mesial position laterals are pretty clear between the species. To compound the hastalis problem, throw in a transitional tooth from I. oxyrhinchus, and you can add another wrinkle to the lateral hastalis problem.
For sure this topic makes for an excellent conversation, and reminds us why more research and future discovery is always important in every field of science.