Hmm, the WP article said that Dreadnoughtus weighed more than Boeing 737, so I was expecting it to be at least similarly sized. Was confused for a while because the 737 is much bigger in the chart.
Turns out the plane in the chart is the biggest version of the 737 series, which is nearly 50% longer and heavier than the smallest version. The weight shown in the chart (44 tonnes) is the 737-900's empty weight. When fully loaded, it can weigh up to 85 tonnes, much heavier than the Dreadnoughtus. The weight mentioned in the WP article (50 tonnes) is for a fully loaded 737-100, the oldest and smallest version.
(From http://arstechnica.com/science/2014/09/meet-dreadnoughtus-th...)