Eusauropoda

Eusauropods Temporal range: Early Jurassic—Late Cretaceous, 175–66 Ma PreЄ Є O S D C P T J K Pg N
Skull of Jobaria
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Order:	Saurischia
Suborder:	†Sauropodomorpha
Clade:	†Gravisauria
Clade:	†Eusauropoda Upchurch, 1995
Subgroups
†Abrosaurus †Algoasaurus †Amygdalodon †Asiatosaurus †Atlasaurus †Chebsaurus †Chuanjiesaurus †Ferganasaurus †Jobaria †Liubangosaurus †Nebulasaurus †Pukyongosaurus †Qinlingosaurus †Shunosaurus †Volkheimeria †Xianshanosaurus †Cetiosauridae †Mamenchisauridae †Turiasauria †Neosauropoda

Eusauropoda (meaning "true sauropods") is a derived clade of sauropod dinosaurs. Eusauropods represent the node-based group that includes all descendant sauropods starting with the basal eusauropods of Shunosaurus, and possibly Barapasaurus, and Amygdalodon, but excluding Vulcanodon and Rhoetosaurus. The Eusauropoda was coined in 1995 by Paul Upchurch to create a monophyletic new taxonomic group that would include all sauropods, except for the vulcanodontids.

Eusauropoda are herbivorous, quadrupedal, and have long necks. They have been found in South America, Europe, North America, China, Australia, and Africa. The temporal range of Eusauropoda ranges from the early Jurassic to the Latest Cretaceous periods. The most basal forms of eusauropods are not well known and because the cranial material for the Vulcanodon is not available, and the distribution of some of these shared derived traits that distinguish Eusauropoda is still completely clear.

Eusauropods are long-necked, strictly herbivorous, obligate quadrupedals. They have a highly specialized set of skeletal adaptions due to their large size, and are graviportal.

Yates and Upchurch described eusauropod evolution as moving towards a “bulk-browsing mode of feeding”. They describe the development of lateral plates on the alveolar margins of tooth-bearing bones. These plates can be used to strip foliage, the eusauropod’s “U-shaped” jaws create a wide bite, and their loss of “fleshy cheeks” increased the gape. The crowns of eusauropod teeth also have “wrinkled enamel textures”, but it is unclear what this meant for their feeding habits.

The skull length of the basal eusauropod, Patagosaurus is about 60 centimetres (24 in). One of the most basal eusauropods, Shunosaurus, has two characteristic features of the eusauropod elongated neck: the incorporation of the equivalent of the first dorsal vertebra into the cervical region of the spine, and the addition of two cervical vertebra in the middle of the cervical vertebrae.

Other synapomorphies of Eusauropoda includes a retracted position of the external nares. Unlike prosauropods and theropods, which have a snout with smooth, unprotruding alveolar and subnarial regions, eusauropods have snouts with “stepped anterior margins”. Further distinguishing features of eusauropods include the absence of the contact between the squamosal and the quadratojugal, the absence of the anterior process of the prefrontal, and a distally elongated anterior ramus of the quadratojugal. Separating the anteroventral process of the nasal from the posterolateral process of the premaxilla, eusauropods also have a long maxilla that forms the posteroventral margin of the external naris.

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Wikipedia