Dreadnoughtus

Dreadnoughtus, meaning "fearing nothing," is a genus of giant titanosaurian sauropod dinosaur discovered in the Upper Cretaceous (Campanian-Maastrichtian; 84–66 Ma) Cerro Fortaleza Formation of Argentina. It is one of the largest of all known terrestrial vertebrates, possessing the greatest mass of any land animal that can be calculated with reasonable certainty, using limb bone measurements. In terms of skeletal completeness and ability to encode its anatomy into cladistic analyses,Dreadnoughtus schrani is the most complete gigantic titanosaurian sauropod din

osaur. It is also perhaps the heaviest dinosaur known, as the one known specimen was a sub-adult.

Mass
Dreadnoughtus schrani was substantially more massive than any other supermassive dinosaur for which mass can be accurately calculated. Using Equation 1 of Campione and Evans , which allows inference of body mass of a quadrupedal animal solely from the minimum circumference of the shaft of its humerus and femur, the Dreadnoughtus type specimen weighed approximately 59.3 metric tons (65 short tons). By comparison, the animal's weight was more than eight and a half times that of a male African elephant and even exceeded the Boeing 737-900 airliner by several tons when taking the estimate from the description. Linear bone measurements indicate the holotype individual was approximately 26 metres (85 ft) long and stood about 2 stories tall. Its neck is estimated to have been 11.3 m long, its torso 4 m long, and its tail 8.7 m long.

Distinctive features
Composite image of the tail bones of the Dreadnoughtus schrani type specimen. This individual’s tail would have been 30 feet in length.

The tail of Dreadnoughtus schrani has several characteristic features included in the diagnosis of the species. The first vertebra of the tail has a ridge on its ventral surface called a keel. In the first third of the tail the bases of the neural spines are extensively subdivided into cavities caused by contact with air sacs (part of the dinosaur’s respiratory system). In addition, the anterior and posterior boundaries of these neural spines have distinct ridges (pre- and postspinal laminae) connecting them to the pre- and postzygapophyses (the articulation points of the neural arches). In the middle of its tail, the vertebrae have a triangular process that extends over the centrum towards each preceding vertebra.

Just like modern archosaurs with tails (for example crocodilians, Dreadnoughtus schrani had bones below the vertebrae called chevrons or haemel arches. These bones connect with the ventral surface of the vertebrae and are “Y” shaped when viewed anteriorly. In Dreadnoughtus schrani the bottom stem of the “Y” is broadly expanded, likely for the attachment of muscles.