DinoBlag: Dicraeosauridae

A DinoBlag first: a whole family of dinosaurs. The Dicraeosauridae was a family of diplodocoid sauropods, related to diplodocids such as Diplodocus, Apatosaurus, and Barosaurus. They are, however, distinguished from these dinosaurs by their shorter necks and smaller size. Three species are known of this family thus far: Dicraeosaurus, Amargasaurus, and Brachytrachelopan.

The type species, Dicraeosaurus, was described by Werner Janensch in 1914 for fossils found in the late Jurassic Tendaguru Formation, a fossil formation in Tanzania which also bears Giraffatitan and Kentrosaurus fossils. It is the largest dinosaur in the above diagram, at 41 feet in length. It was named "bifurcated lizard" for the set of small spines on its back.

Another species was not added to the family (named in 1929) until 1991, when the distinctive Amargasaurus was described. It had a set of tall spines running down the length of its neck. At 33 feet, it was smaller than Dicraeosaurus but larger than Brachytrachelopan. It was described by Leonardo Salgado and Jose Bonaparte, from the Cretaceous of Argentina.

The smallest species in this diagram, Brachytrachelopan, was described by Oliver Rauhut et al. in 2005 for fossils also found in Argentina. It had the shortest neck in the family. Indeed, the shortest neck of any sauropod. Its name, "short-necked Pan", in reference to the Greek god of shepherds.

This family was native to the southern continents of Gondwana, and must have migrated here from the northern continents before they broke away from the north, around 140 million years ago, but after the diplodocoids came into existence, 154 million years ago. That is, of course, unless the order Diplodocoidea came into being on the southern continents. Dicraeosauridae is classified either as the most inclusive clade containing Dicraeosaurus but not Diplodocus, or as any diplodocoid more closely related to Dicraeosaurus than Diplodocus.

The diagram at the top was created by Nobu Tamura, and is used here under the GNU Free Documentation License.