The mystery of the other rearing sauropod of the Egidio Feruglio museum

Way back in 2014, John Hutchinson posted some photos from the Museum of Paleontology Egidio Feruglio in Trelew city, Patagonia, Argentina. John’s original tweets are long gone (quite rightly), but happily we reposted the photos on SV-POW!, so they live on. John’s first photo showed what we now known to be Epachthosaurus. But the second photo is more interesting for our present purposes: John R. Hutchinson ‏@JohnRHutchinson@MikeTaylor Here’s the wide view of that exhibit, with about-to-be-squished abelisaur and sulking Amargasaurus. This also prominently features the Epachthosaurus mount. But as you can see, the foreground also shows another, smaller, sauropod — also in a rearing pose. But we don’t know what it is. (In a comment, Nima suggested “The smaller one may be a Neuquensaurus with a very wrong Giraffatitan-based skull model” but gave no reason for this ID.) So I went to look for other photos of the same exhibit. Wikimedia, which is often the best source, has 145 photos of the…