Acipenseriformes are an incredibly successful order of bony fish, first appearing in the early Jurassic and still having members surviving to this day including Sturgeon and Paddlefish. They are also one of the first orders of Ray-finned fish to have evolved.

Acipenseriformes are most notably characterised by their partially ossified (bony) skeletons while still retaining much cartilage. The only described member of this order found within the London Clay is Acipenser toliapicus which is known from only partial remains including dermal scutes and fins. 

A modern comparison would be the European Sea Sturgeon (Acipenser sturio) pictured here showing the 5 lateral rows of dermal scutes rather than scales.

(Credit: Photo by Hans from Pixabay)