The Mega-Legus

So, we are busy under the stairs jack-hammering out the new bedroom. The hole is now impessively deep and Dexter and I are waist deep when we find the dinosaur bone.
'I think we are on to something here,' I say. I rub the dirt off- what is most likely- a bit of its leg.
'Here's another one,' says Dexter, hauling the other leg bit out of the soil.
We study the two legs.
'Do you think there's any more of it?' I whisper. 'I mean maybe we can get it named after us, like Wilfasaurus Dex.'
'Dextersaurus Wilf,' says Dexter.
'No, because that does not sound right and it is my house,' I point out. So we have a bit of a scuffle and I fall back onto yet another bone. 'It must be an arm,' I say, even though it looks like the other legs.
And Dexter gets quite excited and starts jammering the jack all over the place and the hole gets deeper much quicker. 'There's more!' he shouts and pulls out loads of bones. 'This dinosaur has alot of legs!' he says. 'The Mega-Legus!'
I crawl along into the massive tunnel to look for more dinosaur evidence and that is when I hear the noise; a sort of shuffling and growling, getting closer.
'There's something else down here,' I whisper. Dexter crawls into the tunnel. 'Listen.'
We put our ears to the wall of mud.
A hideous claw reaches through the tumbling dirt. There is some screaming, mostly from Dexter. We scrabble back too late. A pair of open jaws with long fangs clamped down over a Mega-Legus bone, shoves its way through the hole.
'There's masses of them!' screeches Dexter, 'it's an invasion!'
'WILFRED?!' calls a voice from above. 'WILFRED!' It's Mrs Next-Door.
'Get out of here!' I shout. 'Save yourself!'