So I'm not going mad. Not quite anyway.
On Sunday I browsed to the Local Guardian website and they had an excellent April Fool gag about a dinosaur skeleton (the fabled 'Cheamosaurus') being found in Nonsuch Park. I fully intended to post about it on Monday morning but when Monday came the article had entirely disappeared from their site!! After much huffing and puffing Google's webcache has coughed up an archived version here, which I suggest you read before continuing.
You'll notice that the tone of the article is quite straight-faced, which leads me back to my question in the title. Were the Guardian writers perpetrating the gag or was it them who got pranked by some joker? The reported discovered of the bones was one Ross Geller, otherwise known as the paleontology-loving character from Friends played by David Schwimmer? They also quote John Hammond of the British Museum, but I think you'll find that John Hammond was the eccentric owner of Jurassic Park.
A more mundane answer could be that a junior staffer put it on the site and the editor went nuts on Monday morning when he found out and had it removed. There's no doubt it's a (very neat) gag but the question for me is still, whose?