The Biggest - Puertasaurus reuili

They seem to have gotten wide due to needing a longer and more efficient digestion, either because of changes in the cretaceous plants (i.e. more toxic?) or as a response to more extreme seasons and more volatile food supply. Funny thing is, we don't know how much longer they could have gotten. The Puertasaurus holotype probably wasn't even the longest.

The mobile island theory is tempting but probably off. Titanosaur legs and feet get more robust in their evolution just as their bodies do. These animal's limbs were evolving to support more mass for their length, so judging by their skeletons, they were not becoming aquatic in any sense. Other sauropods probably didn't have any trouble floating even with a slimmer body. None of them were semi-aquatic, but all were capable of floating and swimming - elephants can swim just fine, and sauropods had more attachment points for limb muscles, so likely more precise movements. The overall density of sauropods was, ton for ton, less than most other animals because of all the air sacs in their bones. This was true of brachiosaurs, diplodocoids, mamenchisaurs, etc. just as it was for titanosaurs.

Chris Masna actually did that part. I designed the Puertasaurus.

Also, hummingbirds are dinosaurs by definition, as all birds are highly derived theropods from the coelurosaur line.

Thanks very much!

Amphicoelias is totally valid - in the sense of it being a valid genus with valid type material. However the type material (Amphicoelias altus) is from an animal no bigger than Diplodocus.

Amphicoelias fragillimus, the near-mythical giant vertebra that got lost, was only about 40% of the vertebra (if the published drawing can be believed) but based on that a 2m+ tall reconstruction has been drawn for the full bone by both Cope and Ken Carpenter.

For being a bone that no longer exists, it's definitely extremely popular. But the fact is, this isn't the biggest dinosaur we have currently existing fossil proof for. If more bones are ever found, it may actually need its own genus separate from Amphicoelias, the proportions are a bit different from A. altus, but not enough to definitively erect a new genus. The problem with this animal is not so much its validity (the bone is no longer around to analyze) but the fact that it's so poorly documentes (a single paper from Cope, and it isn't even the main focus of the paper). Cope could have made a scaling error, or a typo. The discovery was so obscure that for nearly a century nobody paid it any attention in major paleo-journals. So the real issue is that it wasn't really a big deal until the 1990s (and until the 1980s even PhDs thought there was nothing bigger than Brachiosaurus, despite larger and more massive sauropods (some still as yet undescribed) being known from Argentina since the 1920s (and possibly even since the late 1800s).

That said, there are some footprints scattered around the planet that could have been made by an A. fragillimus-sized creature. None of them are in the Morrison, but that doesn't rule out their discovery. But when you scale off of footprints, you really run into some serious problems. Unless you can scale a bigger animal from the same family off of bones, I'd avoid scaling from footprints, just don't do it! There's too much margin of error either way, either from splaying of the heel pads, or conversely from prints with caved-in edges that are too eroded to tell if they caved in. (for Breviparopus, I kept in mind that "Brachiosaurus" nougaredi can actually be scaled to a larger size based on a pretty huge partial sacrum, so Breviparopus is not a record-breaker even in Brachiosauridae - or even if you put it in another family.)

The average blue whale is less than 65 tonnes in mass, it's not larger at all than Puertasaurus.

[link]

Blue whales were nowhere near the actual largest animal that ever lived title.

The problem is that people commonly take the largest specimens as the only figures while ignoring the plethora of more average specimens.