Barosaurus, Diplodocus, and Dryosaurus
Barosaurus stands among some puny Diplodocus while some tinsey Dryosaurus walk by, about 145 million years ago in North America.
Barosaurus has generally been thought to be a moderately large sauropod, roughly the size of the many famous Diplodocus mounted casts you can see the world over. However Mike Taylor and Matt Wedel (of SV-pow! fame) argue that some truly enormous neck vertebra belong to Barosaurus giving it a neck seventeen metres long, and making Barosaurus a horrifyingly colosssal gargantuan thumping great mountain of a beast. It is also an exceptionally beautiful sauropod.
I used Scott Hartman's skeletals for reference.