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.

And the First Dinosaur of the New Year Is...

(Pictured: Not Texacephale, but its relative Prenocephale)
Texacephale langstoni! This dinosaur was described yesterday from cranial remains found in the Big Bend region of Texas. It has been found to be a relatively pachycephalosaur from the late Campanian in the Cretaceous.

It's helped to rewrite pachycephalosaur taxonomy, too. Classification of this dinosaur has shown that pachycephalosaurs found in Asia, such as Homalocephale and Prenocephale form a monophyletic group. A monophyletic group is determined by whether or not the common ancestor of all members of the group would be considered of that group. For example, the common ancestor of an ostrich and a sparrow would have feathers, wings, and be warm-blooded, and therefore a bird. This means that Aves is a monophyletic group. Whereas the rhino's ancestor is related to horses, an elephant's to seacows, and a hippo's to pigs, which makes the group Pachydermata a non-monophyletic group.

And, surprisingly, analysis of its skull has revived the debate over whether or not pachycephalosaurs could have used their skulls in combat. And here I was, betting on the first dinosaur of 2010 to be yet another theropod.

Happy New Year!

It's 2010! A good new year to whoever may be reading this. Here's hoping that this new decade brings plenty of new dinosaurs into the realm of science, and that maybe, just maybe, we'll see some good dinosaur documentaries (for once)!