Sauropelta (/ˌsɔːroʊˈpɛltə/ SOR-oh-PEL-tə; meaning 'lizard shield') is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species (S. edwardsorum) has been named although others may have existed. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of Wyoming, Montana, and possibly Utah. It is also the earliest known genus of nodosaurid; most of its remains are found in a section of the Cloverly Formation dated to 108.5 million years ago.
It was a medium-sized nodosaurid, measuring about 6 metres (19.7 ft) long. Sauropelta had a distinctively long tail which made up about half of its body length. Although its body was smaller than a modern black rhinoceros, Sauropelta was about the same mass, weighing in at about 2 metric tons (2.2 short tons). The extra weight was largely due to its extensive covering of bony armor, including the characteristically large spines projecting from its neck.
Sauropelta was a heavily built quadrupedal herbivore with a body length of approximately 5–6 metres (16–20 ft) and a body mass of 1.5–2 t (1.7–2.2 short tons).[1][2] The skull was triangular when viewed from above, with the rear end wider than the tapering snout. One skull measured 35 centimeters (13.75 in) in width at its widest point, behind the eyes.[3] Unlike some other nodosaurids, the roof of the skull was characteristically flat, not domed. The roof of the skull was very thick and covered in flat, bony plates that are so tightly fused that there appear to be no sutures (boundaries) like the ones seen in Panoplosaurus, Pawpawsaurus, Silvisaurus, and many other ankylosaurs. This could also be an artifact of preservation or preparation. As in other ankylosaurs, thick triangular scutes projected from the postorbital bone, above and behind the eyes, as well as the jugal bone, below and behind the eyes.[3] More typically for nodosaurids, leaf-shaped teeth lined both upper and lower jaws, used for cutting plant material. The front end of the skull is unknown, but there would have been a sharp bony ridge (tomium) at the end of both upper and lower jaws, as seen in other ankylosaurs. This ridge probably would have supported a keratinous beak.[4]
The tail of Sauropelta was characteristically long and made up nearly half of the body length. One skeleton preserved forty caudal (tail) vertebrae, although some were missing, suggesting that the true number of caudal vertebrae may have exceeded fifty. Ossified tendons stiffened the tail along its length. Like other ankylosaurs, Sauropelta had a wide body, with a very broad pelvis and ribcage. The forelimbs were shorter than the hindlimbs, which resulted in an arched back, with the highest point over the hips. Its feet, limbs, shoulders, and pelvis were all very stoutly constructed and reinforced to support a great deal of weight.[1]