Dicraeosauridae

Dicraeosauridae is a family of diplodocoid 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 or Middle Jurassic to the Early Cretaceous. Few dicraeosaurids survived into the Cretaceous, the youngest of which was Amargasaurus.

Classification

Dicraeosaurids are a part of Diplodocoidea and are the sister group to Diploidocidae. In the past two decades, the known diversity of the group has doubled. A 2016 reappraisal of Amargatitanis has placed it into the Dicraeosauridae, as well. In 2018 a new genus, Pilmatueia, was described. 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. == Phylogeny ==

Phylogeny

There have been several different proposed phylogenies of Dicraeosauridae and the intra-group cladistics are not resolved. Suuwassea is variably positioned as either a basal dicraeosaurid or a basal diplodocoid. The phylogeny published by Tschopp and colleagues in 2015 is as follows: == Paleobiology ==

Paleobiology

Feeding behavior As sauropods, dicraeosaurids are obligate herbivores. Due to their relatively small necks and skull shape, it has been deduced that dicraeosaurids and diplodocids primarily browsed close to the ground or at mid height. However, compared to its known relatives, Dicraeosaurus is unique in that it has an equal number of teeth in the upper and lower jaw, though teeth in the lower jaw are replaced more slowly. They are 10–13 meters in body length. They share thirteen unambiguous synapomorphies including dorsal vertebrae without pleurocoels, the presence of a ventrally directed prong on the squamosal, and a subtriangular-shaped dentary symphysis. == Distribution and evolution ==

Distribution and evolution

Early Dicraeosaurid specimens have been found in three continents - Africa, South America, and North America. The distribution of species is primarily Gondwonan, with the exception of the North American Suuwassea. The presence of Suuwassea in North America is unique among dicraeosaurids, therefore making the proper taxonomic classification of Suuwassea essential. The group likely first diverged from the diplodocids in the middle Jurassic in North America and subsequently dispersed into Gondwana, with the most diversity in East Africa and South America. ==Sources==

Source: Wikipedia ↗

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