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RE: Dino/bird amphibians & Carcharocles [Carcharodon] megalodon
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.
The fear of losing an iconic name extends beyond extinct sharks. One
well-known (and well-meaning) dinosaur paleontologist once made a valiant
effort to "save" the iconic sauropod genus _Brontosaurus_. It required some
fancy taxonomic footwork that was not at all convincing - and focused mainly
on trying to split _ajax_ off from _excelsus_.
_C.megalodon_ truly is the _T.rex_ of the deep, for the paleo-fish guys.
True. Heaven forfend that the genus _Tyrannosaurus_ be sunk - say as a
junior synonym of _Manospondylus_. (Of course, this will probably never
ever happen.) Also, not that this means very much considering that we are
comparing an aquatic elasmobranch with a terrestrial archosaur, but both _T.
rex_ and _C. megalodon_ attained around the same body length: around 12-14m.
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
So am I. The trouble with shark teeth is that, as you say, they are so
rarely preserved attached to jaws or bones, due to their cartilaginous
skeletons. Many fossil shark phylogenies tend to be intuitive, and rely on
'trends' in tooth morphology identified by an individual researcher.
Sometimes we are blessed with fossil shark skeletons (such as the beautiful
_Scapanorhynchus_ fossils), but these are few and far between. There are
some bones of _C. megalodon_, but these are only vertebrae AFAIK, and don't
shed much light on its relationships. We also have bones from the victims
of _C. megalodon_, such as cetotheriids preserved with deep gashes in their