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COELACANTHS...



Hi all. Forgive me, but I've just got to comment on this one.

In pointing out the falsehood of the notion that lineages without small
representatives are doomed, Ron Orenstein said..

> For example, the coelacanths exist today because a quite large form outlived
> its smaller relatives.

More myths and misinterpretations are attached to the evolution and fossil
record of coelacanths (Actinistia) than any other group of vertebrates, mostly
because they are frequently employed as 'ghost lineage' models. 

Recently, it has become popular to point out how radically different _Latimeria_
is from its fossil relatives. For example, it's big (about 1-1.5 m) whereas most
fossil coelacanths are piddly little things (less than 40 cm). Oops. An outdated
myth. _Megalocoelacanthus_, a Camp-Maastrichtian coelacanth described by
Schwimmer _et al_. in 1994, was HUGE: 3-3.5 m long. So big, in fact, its bones
were long misidentified as those of a mosasaur. So you could argue
parsimoniously that the coelacanthid lineage is dwarfed (uh oh.. here we go
again..).

Note another glaring problem in the dogma here.. just about everywhere you look,
you'll read that 'coelacanths vanished from the fossil record at the end of the
Cretaceous, 65 Ma ago'. Well, until 1994 - and the description of
_Megalocoelacanthus_ - this was not the case. The very last fossil coelacanth
was _Macropoma_ from the Santonian.. about 100 Ma old or so. OK, so now it _is_
the case (i.e. the most recent fossil coelacanths *are* from the end of the
Cretaceous), but those who said it prior to 1994 were just lying. Of course,
there is a mention somewhere in the literature of a Tertiary coelacanth. In best
tradition, I've just gone and lost the dam citation.

And while on the subject, coelacanths are now officially recorded from
Madagascan waters if you didn't know. And megamouth sharks are in the Atlantic..
both off west Africa (Senegal) and Brazil. Add to that the new ziphiid whale
_Mesoplodon bahamondi_.. To use a recent quote "Obviously we have no idea what's
down there". 

"Speaking of happiness, you never thought of mine"

DARREN NAISH
dwn194@soton.ac.uk