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Re: Extinct vs Disappeared



> (unless we are lucky enough to find the last Stegosaurus
> that ever lived).
> How big is this gap, or "range extension"? It can be very
> large; the
> classic example is the coelacanth, which disappears from
> the fossil record
> after the Cretaceous but actually is not extinct at all.

And yet, it is just "hanging on by a thread" just two species in two isolated 
locations, with small numbers.

That lineage's future looks pretty bleak.
I doubt it will be long (relatively speaking) before it really is extinct.
In such low numbers, it may simply be luck we found them before they did go 
extinct.
There may have been other lineages from the cretaceous that lived in an 
isolated geographic location... extinct for practical/evolutionary purposes, 
but continuing on until something in their tiny geographic pocket changes, or 
some animal's behavior changes, or population genetics shift, or an invasive 
species comes along...

Never say Never in biology..... but I would say it is highly likely that 
Coelacanths will never again diversify and radiate.