dicraeosauridae

BRACHYTRACHELOPAN
“Short-necked Pan”
Late Jurassic, 150 million years ago (uncertain)

This unique sauropod measured only 30 feet in length. It set itself apart from its relatives with its unusually short neck – less than a quarter of its body length. While species like Diplodocus evolved longer and longer necks along the course of the evolutionary arms race, Brachytrachelopan practiced an adaptation strategy commonly known as “giving up.”

Dyslocosaurus polyonychius

Source: http://dino.wikia.com/wiki/Dyslocosaurus

Name: Dyslocosaurus polyonychius

Name Meaning: Hard to place lizard

First Described: 1992

Described By: Mcintosh, Coombs & Russell 

ClassificationDinosauria, Saurischia, Eusaurischia, Sauropodomorpha, Plateosauria, Massopoda, Sauropodiformes, Anchisauria, Sauropoda, Gravisauria, Eusauropoda, Neosauropoda, Diplodocoidea, Diplodocimorpha, Flagellicaudata, Dicraeosauridae?

Dyslocosaurus is a relatively little-known sauropod from the Kimmeridgian to Tithonian ages of the Late Jurassic, from about 155.7 to 145.5 million years ago. It was found in the Lance Creek area from east Wyoming, and was a dicraeosaurid. It was a unique member of this group in having four or even five claws on the feet, where most other animals in this group only had three. This could mean that it is the same as the ichonospecies Brontopodus birdi from the Early Cretaceous - ichonospecies meaning a species of organism described based on an ichnofossil, or the fossilized work of an organism - in this specific case, a trackway. We cannot always exactly match up ichnofossils to their bone-identified counterparts; however, the fact that a diplodocoid trackway was found with four claw marks instead of three could link these two animals. Though it was briefly though to be a chimera, the Tschopp et al. 2015 analysis found it to be a valid genus. It was a large, quadrupedal herbivore, like most members of Sauropoda. 

Sources: 

https://en.wikipedia.org/wiki/Dyslocosaurus

http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=157545

Shout out goes to virtual-water!