Ammonite (or cogs of time)

Ammonite fossils are very common here in Keynsham town, but I've never noticed this before (despite it being perfectly visible in the park). I have no idea about the origin of this rock which has a number of ammonites bedded into it, looking for all the world like some ancient clock mechanism of cogs (maybe it is!). I have no further insight but I thought you may be interested to see it!