The diplodocid sauropod Barosaurus is best known from the spectacular mounted skeleton in the atrium of the American Museum of Natural History (AMNH).
Apart from the disproportionately long neck it is similar in size to Diplodocus
But did Barosaurus get bigger?
BYU field jacket 3GR was collected from the Jensen/Jensen quarry, Utah, in 1966 but only recently prepared.
It contains three cervical vertebrae, designated A, B and C, anterior to posterior.
They are referred to Barosaurus based on:
Based on spine bifurcation, vertebra C is C9-C11.
The centra of the AMNH cervicals C9-11 are 685, 737 and 775 mm long.
That of vertebra C measures 1220 mm, making it 1.57-1.78 times longer.
This suggests a neck length of 13.3-15.1 m based on 8.5 m for the AMNH specimen.
BYU 9024 is an even larger cervical vertebra, referred to Supersaurus.
It is indistinguishable from C9 of Barosaurus based on the characters above.
(The holotype is a scapula which has never been diagnosed and is not obviously different from those of other diplodocids.)
At 1370 mm in total length, the giant cervical is exactly twice the length of the AMNH C9.
This suggests a neck 17 m long.
Supersaurus seems to be a Barosaurus twice the size of better known specimens.
That makes is comparable to Amphicoelias fragillimus, which is more or less an apocryphal Diplodocus twice the size of the better known specimens.
That's why I can readily believe in big-ass Amphicoelias.
And in Bruhathkayosaurus.
(See also: the big-ass OMNH apatosaur)
Jim Jensen's "big three":
First known from a Reader's Digest article.
Brian Curtice and colleagues synonymised first Ultrasaurus and then Dystylosaurus with Supersaurus.
Dystylosaurus has also been referred to Supersaurus.
The holotype and only vertebra is clearly a diplodocid anterior dorsal, due to:
But it cannot be assigned to any known diplodocid because of:
It may be a valid, distinct genus.
(Cinderella and the Ugly Sisters.)