Haestasaurus

Haestasaurus is known from a left upper arm bone (humerus), a forearm bone (ulna), a radius, and a skin impression. The skin was the first dinosaur skin ever recognized by science.12

Scientists created the new name Haestasaurus in 2015 because the old name Pelorosaurus was used for different bones in earlier studies.1

The fossils come from the Hastings Beds Group, which are about 139 to 133 million years old (Early Cretaceous).4

Haestasaurus had a very thick and strong ulna (forearm bone) but a slim radius next to it. That unusual combination helps scientists tell it apart from other sauropods.1

The upper arm bone had a special hook-like bump on its lower inner corner. This bump is a unique feature not seen in any other sauropod.1

Haestasaurus is classified as a macronarian, a group of sauropods that includes the huge titanosaurs. But scientists are not sure if it was a very early titanosaur or a close cousin.1

The skin impression shows small, round scales. This was the first direct evidence that sauropods had scaly skin, not feathers.2