The leaf is from our Liriodendron tulipifera (American tulip tree) but its beens snagged on its way to earth by a south american shrub called Colletia. I'm fairly sure its Colletia paradoxa and sadly not the brilliantly named and presumably Harry Potter themed Colletia cruciatus. Those big fleshy spines are rather intriguing in the flesh and they look so large you can touch them without getting spiked but that's the beauty of the trap - you can't get anywhere near it without getting nailed by the razor sharp little so and so.
This talk of prehistoric trees (the Liriodendron) and spiky little plants (the Colletia) reminds me of Ethical paleontologist Julia's cycad "bastard" and the rest of her Mesozoic garden. I share Julia's interest in this field and within the initial planting of the arboretum one of the themesI tried to explore was the prehistoric trees - those with real fossil history. Since some of them are now 10+ years old and big enough to be interesting to look at a post on these will follow shortly.