Shark ark

Sharks have interesting dental arrangements which means that there are a lot of shed teeth for palaeoecologists like Dr Charlie Underwood, of London’s Birkbeck College, to collect. He has used them to plot the evolution of modern sharks.

We’ve seen mass extinctions, us neoselachians.
The reason we’re still here today?
We’re good at adapting to new situations
And avoid competition that way.

Our adaptive behaviour is like Noah’s ark.
The proof is this vital distinction:
A primitive cousin, the hybodont shark,
Died out at the K-T extinction.

Our bite has adapted to cut, crunch and tear
At worms, squid, crustaceans and fishes.
Salt water? Fresh water? Done that and been there;
We’ve colonised all sorts of niches.

Our teeth keep on coming, they’re specialised scales
That bud from the skin of our jaw,
Conveyor-belt gnashers; incisors on rails.
When we’ve used ’em, we just make some more.

(The old ones drop out, and geologists spot ’em,
Though many get missed, they’re so small.
The keen ones sieve bagfuls of mud ’til they’ve got ’em –
Maybe five in a kilo, that’s all.)

If you want to survive as a species, you need
Ecological niches with scope
To specialise. But, to be sure you succeed,
Adapt your dentition to cope.

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