Amphicoelias part of Rebbachisauridae?

[suspsy]

https://svpow.com/2018/10/21/what-if-amphicoelias-fragillimus-was-a-rebbachisaurid/

A very intriguing idea! Naturally, it would mean a major reduction in size, but the result would still be a very big sauropod!

[Vidusaurus]

Well A. altus is still (as far as I'm aware) a dubious Diplodocid, which is why the authors named a new species for it. Having looked at the evidence, I think it's pretty likely that "A". fragilimus was a Rebbachisaurid, and it would have been the largest (and I think earliest?) known to date, but without the actual fossil to observe I think it's putting the cart before the horse a bit to name a new genus for it. As a side note, what is it about the Morrison Formation that seems to promote non-Macronarians reaching their maximum size?