“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.”

The double forked lizard, Dicraeosaurus (1914)

Phylum : Chordata
Class : Reptilia
Order : Saurischia
Suborder : Sauropodomorpha
Family : Dicraeosauridae
Subfamily : Dicraeosaurinae
Genus : Dicraeosaurus
Species : D. hansemanni, D. sattleri

  • Late Jurassic (155 - 150 Ma)
  • 12 m long and 10 000 kg (size)
  • Tanzania (map)

Dicraeosaurus wasn’t your typical sauropod of the late Jurassic period: this medium-sized (“only” 10 tons or so) plant eater had an unusually short neck and tail, and most important, a series of double-pronged bones that jutted out from the front part of its vertebral column.

Clearly, Dicraeosaurus had prominent spines along its neck and upper back, or possibly even a sail, which would have helped to regulate its body temperature (the latter possibility is less likely, since numerous sauropods besides Dicraeosaurus would have evolved sails if these had been of any adaptive value). You might not be surprised to learn that Dicraeosaurus was closely related to Amargasaurus, an unusually spiny-backed sauropod from South America.