RE: Dino/bird amphibians & Carcharocles [Carcharodon] megalodon

[Jura <pristichampsus@yahoo.com>]

Tim Williams <twilliams_alpha@hotmail.com> wrote:

> In brief, the crux of the issue is whether the
modern > great white shark (_Carcharodon carcharias_)
is more > closely related to the modern mako sharks
(_Isurus_  > spp.) or to the extinct 'mega-toothed'
sharks like   > _Carcharodon megalodon_. Those
researchers who       > believe that _C. carcharias_
is closer to _Isurus_   > advocate putting _C.
megalodon_ in a separate genus, > named
_Carcharocles_. However, it's my understanding > that
most fossil shark researchers favor the other   >
view: that the modern great white is closer to _C.   >
megalodon_ (and other 'mega-toothed' sharks), and    >
_Carcharocles_ is therefore a junior synonym of      >
_Carcharodon_. Nevertheless, _Carcharocles_ is a     >
great name.

+++++++++++++++++++++++++++++++++++++++

>From what I've gathered, this debate seems to swing
back and forth a lot. Recently, though, it's the teeth
of  _Cosmopolitodus_ that seem to strongly suggest
that _Carcharodon carcharius_ really did evolve from
the mako shark line. 

From: 

http://www.elasmo.com/frameMe.html?file=selachin/gw/cvc_intr.html&menu=bin/menu_topics-alt.html

Bottom paragraph:

When this webpage was first uploaded, I had concluded
that there was insufficient basis, at the time, for
the reassignment of Carcharodon to Carcharocles. Since
that time (1998), I had the opportunity to inspect a 5
million year old specimen from Peru (see Sacaco -
Great White Mako?). For me, this specimen broke the
bond between the genus Carcharodon and the species
megalodon. This specimen provided a link to
Carcharodon carcharias' past - it was the sharks then
known as Isurus escheri/hastalis, the broad-toothed
makos, not the megatoothed sharks. By accepting this
evolutionary relationship, I was not only accepting
Carcharocles megalodon, but also hastalis as being a
great white and not a mako. During 1999 and 2000, I
decided to follow Siverson & Ward's lead by slowly
incorporating  Cosmopolitodus into the website for
extinct great whites. Each reader must form their own
opinion, but it is the fossil record that provides the
answers - not credentials or friendships.

The "Great White Mako" mentioned, can be read on here:

http://www.elasmo.com/frameMe.html?file=paleo/sac/sac-gw.html&menu=bin/menu_fauna-alt.html

It is interesting to note that this huge debate was
inspired, not so much from a healthy degree of
skepticism, but more from a fear of losing an iconic
name. 

_C.megalodon_ truly is the _T.rex_ of the deep, for
the paleo-fish guys. 

That aside, it must be a real pain in the butt to only
have teeth and the occasional impression to work with.
I'm so glad reptiles leave bones behind. :)


Jason

"I am impressed by the fact that we know less about many modern [reptile] types 
than we do of many fossil groups." - Alfred S. Romer

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