Xenoposeidon is a species of mid-sized sauropod. This dinosaur was roughly 40-50 ft long and weighed around 10 tons. Xenoposeidon was fairly tall for it's length. It's been estimated to be over 15 feet tall. This is rather large by today's standards, but somewhat small compared to other sauropods. Xenoposeidon lived in Europe about 140 million years ago.