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Dicraeosauridae is a family of Diplodocoidea sauropods who are the sister group to Diplodocidae. Dicraeosaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as Amargasaurus, Suuwassea, Dicraeosaurus, and Brachytrachelopan. Definitive genera of this family have been found in North America, Africa, and South America. The Asian taxa Lingwulong and Tharosaurus have been suggested to be dicraeosaurids, but some authors disagree with this classification. Their temporal range is from the Early Jurassic or Middle Jurassic to the Early Cretaceous. Few dicraeosaurids survived into the Cretaceous, the youngest of which was Amargasaurus.
The group was first described by German paleontologist Werner Janensch in 1914 with the discovery of Dicraeosaurus in Tanzania. (2025). 9780520254084, University of California Press. ISBN 9780520254084 Dicraeosauridae are distinct from other sauropods because of their relatively short neck size and small body size.
The clade is monophyletic and well-supported phylogenetically with thirteen unambiguous synapomorphies uniting it. They diverged from Diplodocidae in the Mid-Jurassic, as evidenced by the diversity of dicraeosaurids in both South America and East Africa when Gondwana was still united by land. However, there is some disagreement among paleontologists on the phylogenetic placement of Suuwassea, the only genus of the Dicraeosauridae to be found in North America. It has been characterized as a basal dicraeosaurid by some and a member of the Diplodocidae by others. The placement of Suuwassea within Dicraeosauridae or Diplodocidae has substantial biogeographic implications for the evolution of Dicraeosauridae.
Dicraeosaurids are differentiated from their sister group, diplodocids, and from most sauropods by their relatively small body size and short necks. Dicraeosaurids are advanced sauropods within the monophyletic clade Neosauropoda, which is generally characterized by gigantism. The relatively small body size of dicraeosaurids make them an important outlier relative to other taxa in Neosauropoda.
Tschopp includes Dyslocosaurus and Dystrophaeus as dicraeosaurids, two genera traditionally not considered to be part of Dicraeosauridae. The specimens of Dystrophaeus viamelae are highly fragmentary, with only a few bones available for study including an ulna, partial scapula, partial dorsal vertebrae, a distal radius, and some metacarpals. Dyslocosaurus polyonychius also has extremely limited fossil evidence that only includes appendicular elements, and the position of it in Tschopp's phylogeny is therefore considered "preliminary".
Several studies, however, do not include even Suuwassea in Dicraeosauridae, such as Sereno et al. (2007); and JD Harris (2006). Other studies, however, recover Suuwassea as a basal dicraeosaurid, including Whitlock (2010) and Salgado et al. (2006).
Recently from the Thar Desert, a dicraeosaurid fossil dating back to 167 million years ago was discovered in 2023. This present-day sweltering expanse of India was a lush green tropical coastline that bordered the Tethys Ocean, serving as a habitat for a diverse range of dinosaurs during the Mesozoic Era. This discovery marks the first of its kind to be unearthed in Asia and is also the oldest specimen ever recorded in the global fossil record.
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