Reply To: Body Size

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Lee Cone

These are certainly interesting questions that are raised.  I do not know if sexual dimorphism is a characteristic in sharks generally, or of particular species within sharks families.  Are females always larger than males?  Victor @vperez is absolutely correct that meg tooth size varies from posterior to anterior in the mouth, as well as the slant shape of lateral vs. anterior.  Further, uppers and lowers have distinct differences in height to width ratios.  To complicate matters, not every meg anterior tooth (from the same position in the mouth) is identical in shape, especially the depth and weight of the tooth.  I have observed this variation even more profoundly in C. angustidens.

These points were discussed in Nebraska during the Edisto River shark tooth identification lesson plan that I led.  When you have enough teeth to look at, you really begin to see subtle differences that exist within a species, and this complicates the process. And this begs the question, is this simply Darwin’s variation within a species or is it something more?   Clearly, meg teeth are impressive teeth regardless of how you relate them to shark body size, but I do think that a formula that would compare tooth size to shark length does need to specify tooth position.  I have seen composite dentitions that have lateral teeth from smaller sharks used for posterior teeth in dentitions for larger sharks.  True posteriors are quite rare and that is why I love to collect them.

Still another consideration is related to the questions: (1) Is shark growth uniform throughout an individual’s life, and (2) Is tooth size related uniformly to length throughout its life?  My guess is that the ratio of tooth size to body size (mass and length) of juveniles would be very different from that of a very old shark.   It would be interesting to compare body mass, body length, and tooth size of modern shark species vs. age, especially as one reaches the upper age limits.  Of course, the problem with meg size estimation is that we do not have any extant modern evolutionary descendants to compare data with, and the relationship with the broad tooth mako and modern great white may have no direct genetic relationship or similarity to megalodon, especially if one subscribes to the Otodus lineage.