Biggest Dinosaur Yet Discovered

An anonymous reader quote the BBC: "Fossilised bones of a dinosaur believed to be the largest creature ever to walk the Earth have been unearthed in Argentina, palaeontologists say. Based on its huge thigh bones, it was 40m (130ft) long and 20m (65ft) tall. Weighing in at 77 tonnes, it was as heavy as 14 African elephants, and seven tonnes heavier than the previous record holder, Argentinosaurus. Scientists believe it is a new species of titanosaur — an enormous herbivore dating from the Late Cretaceous period. A local farm worker first stumbled on the remains in the desert near La Flecha, about 250km (135 miles) west of Trelew, Patagonia."

Does anyone know what the largest possible is?

[mark-t]

We know that mass generally increases with the cube of a creature's height, and the tensile strength of bone can only support so much pressure from a creature's own weight, so it seems that if there should be some limit to how large a creature in earth's gravity can be (and, for the sake of argument, not being provided any additional buoyancy due to being under water, for instance). This particular creature is alleged over 60 feet tall, and more than 10 times the height of a man, which makes it more than 1000 times the mass of a human. Cross sectional area generally increases with the square of height difference, meaning that more than 10 times as much pressure would be exerted on every square inch of a lateral cross section of bone as what human bones endure. Now granted, this creature was not shaped like a man, and having four legs instead of just two could give it some additional advantage in this department. Additionally, it could have denser bones, capable of supporting more weight, but denser bone structure in turn requires more muscle mass to move, and will tend to further increase the creature's size. Still, it seems like there's still got to be a maximum possible size. Does anyone know what this might be?