Subject: Paleocarcharadon megaladon
Date: Fri, 22 Nov 1996 01:49:46 -0800
From: Bill Heim
Reply-To: Sharks and Cartilaginous Fish Discussion
To: SHARK-L@RAVEN.UTC.EDU

I possess fossil teeth of all 3 white shark lineages and when you lay them out the evidence is fairly obvious. Below is a timeline of species. Note that Paleocarcharodon branches off early as does the lineage that leads to Carcharocles megalodon. Carcharodon carcharias arises out of the mako line (which is why they resemble each other so closely). Henri Cappetta places megalodon in a seperate family, OTODONTIDAE vice LAMNIDAE, which I agree with. With a completely different evolutionary history there is no way one can logically lump them into the same genus. Also note that intermediate fossils exist such as irregularly serrated (i.e. with weak, wavy serrations) Isurus teeth (I. escherei) and irregularly serrated Otodus teeth (O. subserratus) as well as teeth with partial serrations, i.e. ones that are serrated only part way up the blade.

Notes:
*	partially or weakly serrate teeth
^	completely serrate teeth (note: some Paleocarcharodon's are only partially serrated and all of them have very irregular serrations)
?	Unable to determine if Otodus arose out of Cretolamna or Cretodus as it shares features of both. More study is indicated.

ILLUSTRATIONS